Another scientific body has debunked bitemark analysis | Hacker News Reader

Another scientific body has debunked bitemark analysis

radleybalko.substack.com

406 pointscolinprince236 comments

https://en.wikipedia.org/wiki/Annie_Dookhan

I find it shocking that there is no "continuous quality assurance" of these labs - for example, one should take the lab as a blackbox, and send 10% known-negatives, 10% known-positives, and 10% random samples from previous batches in every batch, and then evaluate a) how many known positives/negatives turned out right, b) how many samples from previous batches return the same result.

This is just another case of one of those typical double standards that arise from existing in a society where a non-trivial fraction of the population is willing to give the government a free pass for anything short of chucking puppies into a wood chipper on a live stream.

You can bet your ass if these labs were in the business of supplying defense attorneys the info they need to get clients found innocent they'd be QC and government-regulated up to their eyeballs and would get shut down at the drop of the hat for doing shoddy work.

See also: Many telecoms and ISPs will happily provide police records with little formality. If a defense attorney wants to see all the records the cops got (not just the ones that are going to be used by the prosecution in court) they're pretty much up shit creek until a judge tells the business to turn them over.

I think there's also the problem of science that has been elevated as a religion and anything labelled scientific is taken as gospel.

We should all remember this study that showed that 90% of scientific papers weren't reproducible (not science then).

While I have no problem with science itself, scientists are humans, they make mistakes and can be bought.

People have trouble with moderation because moderation requires the skillful exercise of prudential judgement, and since prudence is a virtue, it means that it is something learned and acquired. That we can't verify everything personally and therefore must often rely, for practical reasons, on appropriate trust toward authority does not mean we ought to jump out of the pan of irrational skepticism into the fire of uncritical subservience.

Was that replication crisis study ever successfully reproduced?

Yes. Massively.

Your assertion that 90% of scientific papers aren't reproducible is extremely simplistic. There is a vast difference in reproducibility across the different scientific fields. A lot of the "reproducibility" crisis is taking place in fields that are not even traditionally known as science.

How offen are people bitting people and only being id through the bite marks? Are there people sneaking into bedrooms biting people? I don't get it.

Typically it's a "man bites dog" kind of case. [ducks]

When there are violent struggles, it's not actually that uncommon for bite marks to be present on victim or assistant.

*Source - I've seen lots of episodes of Forensic Files.

Too late to edit but...

*assailant

I'd imagine it's not uncommon for bite marks to be at least one piece of evidence. Victim struggles, bites assailant, cops arrest somebody with a bite mark, suspect insists it's from some fun times with their SO and not from a victim defending themselves, cops call upon their pseudoscientists to "prove" that the bite mark came from the victim. Or another way around, a victim of a violent assault might have been bit while fighting off their attacker. In a grappling scenario, there is definitely a portion of the population who will instinctively use their teeth, from my experience in water polo, I'd reckon about a quarter of people.

do people in water polo really bite each other? Sounds pretty vicious...

I've seen it happen once in over 15 years of playing it on a "Beer-team" level. 25% sounds a bit much but YMMV for region to region and level of play.

Maybe. Might also have something to do with your position. I was a whole set/whole D/bruiser for my high school teams, so I spent a lot more time in direct contact with other players than most.

It's a vicious sport. More so in women's polo, where the brute strength range is a lot smaller than in men's. I played at the highschool level, where the violence is vicious, as opposed to the university level where I'd better describe it as "brutal". Players treat the game as team vs. team vs. referee, so it's basically a melee until you think you can flop a bit to get the ref to kick an opposing player out.

Here's one such example of a biter, not in polo but football: https://www.businessinsider.com/luis-suarez-biting-history-2...

Surely there must be tons of DNA when somebody gets bitten?

Even if the mere presence is not enough for a conviction, it should be enough to disprove that "fun times" explanation.

It's very hard to get a reliable DNA sample from the body of a different person.

There was an HBO documentary series named Autopsy[0] I watched back in the 90s and two crimes stick out. The series mainly followed the case file of a Forensic Pathologist named Dr. Michael Baden.

If I can remember them correctly, one case was a murder that appeared as a break-in and a bite marking found on a garbage bag was tied back to the victim. The other was an inmate that left bite marks on a guard and tied the crime back to the inmate with.

It’s so interesting to see this research now and wonder what would come of those cases now that the main evidence is seemingly unreliable.

[0] https://www.hbo.com/autopsy

Some criminals MO is to bite. Before DNA testing was available, it might be all the cops had as evidence. My person opinion is it is only good enough for a clue, not evidence. I think the same of the blood spatter patterns and when cops do reconstructions of things to determine what happened.

Bloodstain analysis is, for the most part, also crap. [0]

We should be wary of many of the types of physical "evidence" popularized by crime shows; many of them are backed up mostly by propaganda rather than science.

[0] https://scholarship.shu.edu/cgi/viewcontent.cgi?article=2125...

The murder of Sherri Rasmussen [1] comes to mind.

They caught the perpetrator decades later, mainly due to DNA traces left in the bite mark on the victim’s arm.

[1]: https://en.wikipedia.org/wiki/Murder_of_Sherri_Rasmussen

Proves the main thesis of his excellent book

The Cadaver King and the Country Dentist: A True Story of Injustice in the American South

https://www.amazon.com/Cadaver-King-Country-Dentist-Injustic...

"Crime labs" cannot be trusted. They are unaccountable and dependent on police departments for funding. Their results are "good" if people get convicted. That's perverse and contrary to scientific principles. That extends to publications in that field. It's systemically corrupted and needs to be restructured to be independent of police and prosecutors.

Bitemark analysis for which child got into the block of cheddar cheese is dead accurate, though. You will not so easily overturn the convictions.

Lack of incentives for scientific skepticism as a normalized, institutionalized form of academic discourse -- is the problem.

The are a lot of incentives to get 'published' or to get 'sponsored. And there are no incentives to question validity of methods or results (unless these are 'sponsored').

Formalized methodology underpinning scientific skepticism, should be taught as part of first 4 years of college (or even specialized vocational schools).

There are should magazines in every field, dedicated to skepticism, the recent discoveries, methods of analysis, etc. There are should be commercial and tax-payer funded sponsorships available to do just that.

May be, there should be advanced degrees in statistical claim validation methods, and so on.

I sometimes worry that we don’t have a culture of science, but a culture of scientists. Very different things in terms of aggregate output.

This seems like a really straightforward thing to test. If I get a thousand people together, have them each bite 10 human skin analogues, identify the participants and each of their bite records with a GUID, can bite mark analysts map bite records to biters and with what accuracy?

If they can't, why did the courts think they could? Why are we doing the tests for whether or not a method works after making use of that method?

After skimming one of the papers linked in the NIST analysis - it seems bite mark analysis is far below this standard. The analysts being tested had substantial disagreements over whether something was a bite mark and whether it was caused by adult or child teeth. Matching bite marks to a reference mark seems well out of reach.

> This seems like a really straightforward thing to test. If I get a thousand people together, have them each bite 10 human skin analogues, identify the participants and each of their bite records with a GUID, can bite mark analysts map bite records to biters and with what accuracy?

Not quite the same thing. Because that assumes you already know it was one of those people.

More appropriately you should ask the labs "does this bite mark fit any of these 100 people", where none of those people actually caused the bite mark.

Will the lab recognize it was none of them? If they just falsely identify one out of the hundred, that extrapolates to millions of people.

I've been listening to the podcast Your Own Backyard (yes, I occasionally indulge in true crime, sue me!)

There was recently an entire episode dedicated almost entirely to cadaver dog testimony. Well, the dog was not testifying, the handler was.

Now, I have no doubt that cadaver dogs can, and do, find cadavers, and can detect when a cadaver was recently present.

But listening to the testimony of the handler, from their viewpoints, the cadaver dogs are psychic. The ability of their senses verges on mysticism.

I don't doubt that there is value to cadaver dogs - clearly they work, and get results. But the humans who testify on the dogs' behalf have a cult-like behavior about what the dogs can realistically detect, and how they interpret the dogs behaviors.

"... and how they interpret the dogs behaviors."

The interpretation part is huge in many disciplines. If you especially look at high profile cases, you can have experts for each side presenting opposing interpretations (not even involving animals).

Then it's up to the jury to decide which is more believable.

There's your spooky story for the day.

And, unfortunately, "reasonable doubt" is not a reliable fallback in such a situation.

Reasonable is whatever they say it is.

So it seems that "beyond the reasonable doubts" is a fiction unless one can afford really expensive lawyers.

Even expensive lawyers and experts do not always overcome the court of opinion.

At least in the jury I was in, people severely misunderstand reasonable doubt. And they took into consideration the defendant not testifying, as is their right under the 5th Amendment. No matter how I pointed it out they kept saying “if they didn’t have anything to hide, why not testify?”

It’s definitely destroyed my trust in a jury of my peers.

"It’s definitely destroyed my trust in a jury of my peers."

If only they were actual peers. Many of the smart ones know what to say to get out of being on a jury. There are so many people with biases too, and many don't get filtered out because they don't even realize that their belief is based on bias.

>"Many of the smart ones know what to say to get out of being on a jury."

I believe in supremacy of justice as I understand it over a written rule (I know it is flawed but this is me). If I feel that person will be punished unjustly then screw the law and I would vote for nullification as it is my right. I think this will stop from being selected as a juror.

I only recently learned that you can waive your right to a jury, and instead have your case decided by the judge.

I think this would be a very tempting option for me, if I ever found myself in serious legal trouble. I assume a judge would be less susceptible to emotional manipulation, and be intelligent enough to properly weigh the facts.

Of course, then you are at the mercy of one person.

Well actually they will bypass both and offer you a deal you can't refuse.

It's called a plea bargain. "Plea guilty and here is your penalty. And if you don't, here is the stack of charges we'll try to get you for and how much worst it will be. Do you feel lucky, punk?"

Over 95% of cases end this way. Based on exoneration, a fairly significant percentage are actually innocent people who decide that they can't fight it.

If you think this doesn't sound like justice, I absolutely agree.

"and instead have your case decided by the judge."

Oh God no. This is even worse. In my limited experience, judges can be very biased. They tend to be very unaccommodating as to what reasonable doubt is (it's whatever they say it is).

>Then it's up to the jury to decide which is more believable.

And anyone who the prosecutor will stereotype as potentially having too much critical thinking skills or skepticism of the prosecution will get tossed from the jury.

Some of the humans, the subset who's testimony was selected to appear on that show.

A cadaver dog could be useful for finding a carcass, human or otherwise. Once a carcass is found, can't more qualified experts testify about it? Are we talking about cases in which a carcass wasn't found, but was theorized to have been present at some point?! How do we know the carcass was human? How do we know how long ago it was present? If we could be certain of either of those things, how do we know it was the particular human whose murder is being prosecuted?

We can't blame dog enthusiasts for testifying, but it's a judge's job to keep fantasists out. Judges who allow such testimony aren't stupid; they are evil.

When they find a body, it's easy.

It's the cases you'll read about when it says the dog "activated" or "altered" five times on the property, even though nothing was found, and that's somehow used as evidence of something.

That's hideous. Judges who allow that testimony should be impeached and disbarred, at a minimum.

I don't see why judges can't allow bunk testimony, the problem is that juries have been watching way too much CSI:Miami and don't believe any arguments brought up by the defense that forensic 'experts' are reading chicken entrails.

For the same reason that a defendant may not be presented to the jury in handcuffs or in a prison uniform. Because we humans are not able to return to a blank slate, free from biases imparted by information later learned to be false. For methods that are known to be useless, the jury shouldn't be asked to perform the impossible.

Easy to say. But to the extent that it’s easy to get rid of judges they can’t be an effective check on the other branches.

Thread hypothesis is that the judges are encouraging prosecutorial misconduct, i.e. that they are intentionally not acting as a check on the executive branch. For local and state courts, which is what we're talking about, the primary check they embody is against police and prosecutors. When they fail in this duty, absolutely they should be replaced by those who do not fail.

Then the question is, who should get to decide when to replace a judge? Obviously not the executive branch, especially in the context of this particular discussion.

For example, some judges are elected (probably varies by state, but there are some places where that's true), so in those cases a perfectly viable remedy already exists (in theory, at least). Of course, in practice there's nothing to prevent voters from being very pro-prosecutor. Usually the judicial system is the best option for a remedy to that sort of problem, but of course then we're back where we started..

Typically the legislative branch handles impeachment, although in some states the judicial branch would also play a role in the process. We have a norm that officials are not fired for doing their jobs poorly, even to the extent that they intentionally harm people, and that certainly makes various things run more smoothly. Smoothness would have been a more convincing argument back in the day when our government produced acceptable results [0], assuming that day ever occurred. Obviously one would prefer that people not be convicted of murder based on stories told by buffoons about their interactions with dogs. Probably there aren't a great many judges who would allow such a thing. When that has occurred, however, a public proceeding in a legislature would constitute a wonderful reminder for all judges to take their heads out of their asses, which would contribute to justice.

[0] In USA we spend twice as much on health care as any other nation. Our performance against covid has only been better than Peru, Brazil, and several nations in eastern Europe. Every nation in Asia and Africa had fewer deaths per capita than we did.

There's also "dog alerted, after five days of digging we found a single bone fragment 200ft away. Insufficient DNA remains for us to conclusively say it's human, but all the evidence is consistent with human"

That scares the shit out of me if I'm being honest.

years ago I read an article by bruce schneier talking about how he ran an open home network so if someone accessed illegal content he could claim it could have been anyone. His argument was that if it was secured the police would argue it had to have been him.

I got the point but disagreed.

a year or two later I was reading an article about a police officer that got convicted of accessing child pornography on the police computer systems. The chief of police was quoted as saying "we know it was him because he used his password".

My ass went home that night, opened up my home network, and I've ran it that way ever since.

of course it's not that simple, understanding why that chief of police was wrong (I'm not making any claims about whether that police officer did or didn't access that material) in his confidence is what caused me to suddenly strongly agree with Bruce Schneier.

So when I hear things like your dog story, I just know that confidence has to be misplaced, even if I don't fully understand why (although in this case I do).

Those aren't really the same thing. You can go to the next level of detail on the password question. Was the officer reliably in the area, was his password well known, is it trivial for anyone to find the password. Whereas wifi at your home, there are endless ways to get it, plus did you share it with anyone.

Good luck making those arguments to law enforcement.

Arguing with law enforcement is a losing battle. You can beat the rap, but you can't beat the ride, etc.

Or, when a dog's "evidence" is used to get a warrant. The argument is that the right to privacy does not exist for illegal actions, and a dog will only alert for illegal contraband. So a baseless fishing expedition without any reasonable justification is rendered legal based on pseudoscience.

This is like saying "Dont hate the player hate the game"

No I am perfectly capable of rightly placing blame on both. In this context the Cops, prosecutors and judges all have an ethical duty to the truth. All 3 seem to have forgotten that underlying obligation in the system

They want that "win", that conviction, that revenge, or what ever.

So yes I will blame the judge for letting bad "evidence" in that lacks proper foundation, but I will also blame the cop that is presenting the "evidence" and the prosecutor that presented the "evidence"

Our systems have layers for a reason, we can not and should not have to relay solely upon the Judge as the first, last and only line of defense here.

> In this context the Cops, prosecutors and judges all have an ethical duty to the truth. All 3 seem to have forgotten that underlying obligation in the system

Could you clarify: are you referring to every single member of those 3 groups, or just some?

And if it's just some, then roughly speaking, what fraction do you mean, and what evidence supports that?

Depends on which part of that quote...

I believe every single member of all 3 have an ethical duty to the truth

I think a significant number of all 3 groups have forgotten that, or believe something else take precedent further I believe every member of all 3 groups knows about a co-member of the group that has ignored or violated their ethical duty and looked the other way, or actively covered for that abuse

I think it's important to note that cops, prosecutors, judges, etc. are trained and encouraged to "listen to the science" and "don't rely on your gut." Of course, many disregard this, due to corruption or other moral failings. But many do follow this advice, and sometimes it results in presenting faulty evidence simply because they have been taught faulty science.

In addition to rooting out corruption and dismantling immoral incentives, we need to seriously re-examine the forensic science that is the backbone of many cases. People--including judges, juries, cops, and lawyers--are far too willing to blindly trust "science," and it can have extremely scary outcomes. We need more replication of studies and better science education for our criminal justice professionals.

the bigger problem is we have lost the true meaning of "science" or rather the "scientific method" as a huge part of forensic "science" has no connection with the "scientific method" upto and including the foundational "science" of fingerprints which is more of interpretive art than science

Too much of science today is Hypothesis -> Gather Data to support, reject any that does not -> Report Conclusions -> Burn Heretics

Also, in the US precedent sets if something is scientific in the eyes of the court, not science.

well, one potential nefarious use of dogs is the parallel construction of evidence that was gathered illegally in some way. That's, I assume, what psychics are for.

primarily the bad use of cadaver dogs isn’t in finding buried bodies but in allegedly being able to say that the body was somewhere else before it was moved, like the trunk of a car or a bedroom etc. cadaver dogs are basically used to frame suspects by claiming that the dog smelled the dead body somewhere where only the suspect could have been, therefore proving they killed the person. it’s complete bullshit. can dogs detect corpses? i think they can. can they detect where a corpse was, but no longer is, days or weeks or even years later? absolutely not, but cadaver dog handlers will testify under oath that they can

> (yes, I occasionally indulge in true crime, sue me!)

Sounds like civil court rather than criminal.

"2biteencryption", name checks out

Similarly, handler beliefs affect scent detection dog outcomes to at least some degree as indicated in this study:

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3078300/

> No conditions contained drug or explosive scent; any alerting response was incorrect

> Within marked conditions, handlers reported that dogs alerted more at marked locations than other locations.

> The overwhelming number of incorrect alerts identified across conditions confirms that handler beliefs affect performance. Further, the directed pattern of alerts in conditions containing a marker compared with the pattern of alerts in the condition with unmarked decoy scent suggests that human influence on handler beliefs affects alerts to a greater degree than dog influence on handler beliefs

I found this to be very telling. It at the very least warrants more study. At the worst and in my opinion, warrants elimination of dog scent detection as the sole factor in a search.

Check out this article from the National Detector Dog Association - 'The Double-Blind Attack'. These people seriously don't believe in science.

https://nndda.org/the-double-blind-attack/

Wow!

> Results in confusion and frustration in the canine – As stated previously, under doubleblind testing, the determination of the team’s accuracy cannot be made at the time of the alert. Therefore, to provide or withhold a reward from the canine under such a condition can result in confusing and frustrating the canine, which will lead to an increase chance of incorrect responses.

Juxtapose that with the real world. I am not an expert but I sincerely doubt that K9s in airports get treats every time they correctly identify a illicit source. That is why they are trained constantly(I presume). Testing for one hour or one day will likely not have an effect on the long term ability of the dog to correctly sniff illicit sources.

The NNDDA article is addressing the "double blind attack", which in my opinion is their way of redirecting from the notion that the K9s should not be used as a gold standard to ascertain probable cause. I would have to think more on the subject to comment on reasonable suspicion. If they truly believed in the idea that handlers are benign, they would embrace the double blind process.

Reminds me of audiophiles. When the scientific method is the enemy, you are dealing with some massive psychological effects that people refuse to acknowledge.

Suppose you have a grand piano recording set up something like this https://images.squarespace-cdn.com/content/v1/59e4eb2464b05f... or like this https://i0.wp.com/royerlabs.com/photos/rec_tips/piano/Mancin...

Not only you have a multitrack recording to play with when mixing/mastering, but the tracks are naturally frequency weighted due to spatial positioning. Mix these tracks into stereo with some panning and play it on a decent set up with large-ish (say 5m) scene. You end up with unnaturally large grand piano spanning the whole scene. It does not sound "natural", but gives fake perception of "scene".

The whole audio field is weird constant chase between production, recording and reproduction (e.g. in the 90s V shaped frequency profile used to be quite prevalent to sound good on boomboxes) which gives perfect breeding grounds for audiophilic mysticism. No set up will ever be able to "naturally reproduce" both rock concert and chamber orchestra.

I have noticed that there are two types of audiophiles. The first kind has certain collection of records and strive for a set up that gives them the same goosebumps they felt first time hearing the recording/concert, the second kind lives off giving goosebumps to their audiophile friends bringing their own records. Both live in constant grind for perfection that they will never achieve.

> I sincerely doubt that K9s in airports get treats every time they correctly identify a illicit source.

Why do you doubt that? When people say "treat" they don't mean a full day at the spa. It's a bite of something tasty, or a bit of play with a tennis ball while the dog handler says "goood booooooy".

they absolutely treat the dog for finding contraband. that’s how you train them to alert on the smell. the problem is that this means they might alert for nothing at all, just because they want a treat

Wow. Everything in that article reads as an admission that canine units are utterly useless, even as the article tries to defend their use. The primary argument seems to be that dogs need constant and immediate reinforcement in order to be effective, and therefore double-blind studies are not effective measurements. This same argument would also imply that canine units are not effective in the field, since the handler wouldn't be able to provide accurate reinforcement.

If that would be treated seriously, it would mean that detector dogs are impossible to use in case where they need to find or detect something.

So they are completely useless.

Is nndda.org actually serious representation of them?

Oh, they're extremely useful, just not for the thing you think. They manufacture cause for searches. It's a form of evidence laundering.

And yes, the NNDDA is one of several organizations that certifies police dogs.

A bit similar in the story of the counting horse from Germany in the early 20th century: https://en.m.wikipedia.org/wiki/Clever_Hans

My wife had tulip bulbs from Amsterdam in her carryon and the beagle at customs immediately identified her. It was amazing.

That said I’m sure even without training them to do so they look to their handlers for cues.

I know guys who smoked a lot of pot when they were younger. Would even fly with a small stash.

Never got caught or had a dog alert on them. They also didn't look like stoners. Whatever your stereotype is of how a stoner looks (and there are a few).

The 9/11 attackers were all clean shaven and dressed in business casual.

While I've seen roaming dogs in airports this was in customs and she passed by everyone. I'd certainly tell those friends to not try that on an international flight judging by that experience.

My one friend came from an English family so mostly flew to the UK.

As I understand it, buying drugs there is not a problem. No need to fly with them.

> immediately identified her.

How many others were "immediately identified" but were not carrying bulbs?

0. The handler even immediately asked if we had tulip bulbs - though I'm guessing that was just because she knew where we came from.

Was she aware of the bulbs being a potential issue? Maybe she sweated or showed other signs.

I don't think she was nervous about it as we got them in the airport, though she was confused as to whether or not we needed to declare them.

I had a cop friend directly tell me that there is no point to telling an officer not to search your car. If he feels like it, he will call a K9 unit, and the with that he will have probable cause to search the car. I said what if the dog doesn't detect anything. He laughed and said that doesn't happen.

There is a point. I understand your friends point though. In the USA, not giving them permission allows your lawyer to fight the case on the ground that it was an illegal detention. Case law has set precedent that without reasonable suspicion officers cannot extend your detention in a traffic stop just to bring a dog in(Rodriguez v united states 2015). Never ever give permission to search.

I know he's your friend, but "don't take legal advice from your opponent" applies here. It may be true that they will inevitably find a reason to search your car. It may not be true that the ensuing search will be legal and hold up in court.

Of course, there is a nonzero chance you will not survive to see a court date, but that's a different policing issue.

At this point, I'm convinced sniffer dogs are the dowsing rods of our time: basically just serving as psychological salve to reinforce a feeling of safety.

Are you saying the "use" of sniffer dogs, or that sniffer dogs are unable to accurately determine individual scents ?

The use of sniffer dogs in schools and airports.

I can tell you the drug sniffing dogs in use in Queensland, Australia in the late 2000s absolutely were basically “dowsing rods” (I was involved in illicit things at the time and went past/was sniffed by drug dogs over a dozen times and was never caught or searched despite having illegal drugs on my person, without much of an attempt to hide them). I’ve shown my partner how the handlers give a signal to the dogs to “mark” someone for a “probable cause” search too.

I would be fascinated to know how many and to what extent police techniques that appear to stretch believably are really tools to perform parallel reconstruction and get around shady sources of evidence.

Probably a lot of them. The US justice system has a lot of good things, but parallel reconstruction, constantly using the easiest way to get info even if it is illegal. Of course the latest thing is spying on all of us either through apps on our phones or just asking the phone company directly.

The entire industry, yes industry, of "expert witnesses" is murky.

Not just murky. Surf around and you can find companies offering these types of experts as a service. These experts are often experts in a surprisingly wide variety of fields, too.

> But the humans who testify on the dogs' behalf have a cult-like behavior about what the dogs can realistically detect, and how they interpret the dogs behaviors.

There was a scandal here in .cz regarding forensic odorology using dogs, as a report came out where the authors basically found out they were unable to test it, because the dog-operators either did not understand what is a double-blind experiment, or they even actively sabotaged it. It is then implied that when they do the identification for real, they are not blind to who the suspect/control is. (report, unfortunately only in Czech: https://jenda.hrach.eu/f2/salamoun-testovani-pachovych-stop....; google translate: https://jenda.hrach.eu/f2/salamoun-testovani-pachovych-stop-... )

It's clear that this resistance to being reasonably tested is because the handlers are obviously influencing the dogs. It's freaking irritating. A lot of that is drug war bs. I thought only us law enforcement would be resistant to evaluation.

The more "system" you have the more often you'll hear "sorry, but that's just how the system works" and nobody will ever be able to (or want to) do anything about the problem.

And there's a lot of system around here in EU. Applies to healthcare, social care/security and of course police as well.

I did volunteer search and rescue for a bit and people were split on weather dogs were even useful in that context either. Some people thought they were indispensable and some thought they were useless.

Is this just a general problem in science?

Science is highly objective, but the process of attaining scientific credibility is prone to all kinds of human problems.

Expecting the judicial system to sort through this better than the scientific community seems foolish.

Ideally, a high-enough percentage of scientifically-educated people would mean more skeptical jurors, defense attorneys who more able to challenge experts, and judges more able to keep junk science out entirely.

Bite marks were used to convict Ted Bundy

Mexican here, in my country these type of "evidences" are harder to support / enforce, as long as your lawyer / you are willing to provide enough scientific indication they're not reliable, those evidences are dismissed.

Of course, as any country, there's corruption at every level.

Wonder what's the stance of other countries?

Often these types of evidences are used to get the subject to confess or agree to a plea deal.

(In other words, they're often used "when we know you did it" kind of things.)

The justice industry isn't very pretty, best not to look too closely at it.

I’ve heard the Mexican legal system has really strong rights for defendants. So strong, it’s hard to prosecute corrupt officials.

Found a spelling/grammar/idiom error ("little to know" -> "little to no"). Tried to commend, but I have to pay for that. Tried to click to that persons profile. Have to create an account. This seems like a bad idea...

> Tried to commend

ironic

Muphry's law at play.

So no way to be sure if I bought Jon Voights car?

I'd be curious to see a list of all of the classic cinema police cliche's that have no basis in evidence. So far there's the lie detector, blood spatter analysis, bite marks.. what else?

Wait - blood spatter must follow the rules of physics, so there is some kind of analysis that would be valid, surely?

Reading online I see its still respected lots of places and still taught in forensics. Don't know where that came from.

I think if you read this article you'll see (at least part of) the answer. Not only does a given action have to cause a definable result, the medium upon which the result is deposited has to provide enough detail to read the result back off it, and the people reading the result have to be able to be consistent and accurate in their analysis of that result.

With bite marks, the skin has to hold the bite mark (which it doesn't) and experts have to be able to map it back to real human teeth (which they can't). With blood spatter, there are analogous problems.

Which sounds miles from 'have no basis in evidence'. So that might have been a little hyperbolic.

I'm not sure why you're trying to play devil's advocate on that. The things they are claiming about the analysis techniques literally have no basis in evidence. Saying "blood spatters follow laws of physics" has nothing to do with what the experts are doing now

...and I countered with "the physics surely have validity", which the plentiful science done to date has corroborated.

Not playing devil's advocate; just doing some simple searches and calling out hyperbole.

These days folks have replaced science with advocacy. You know, that thing lawyers do to convince a jury. To the point folks think that you can arrive at a conclusion with advocacy. Instead of looking at the data.

I'd ramble on about how the world is going to pot, because folks thing a sarcastic remark or clever-sounding turn of phrase is 'just as good' as facts. But oh well.

You confused the GP statement about “blood spatter analysis” with a statement about “blood spatter”.

If someone critiques astrology you don’t reply that “planets follow physics”.

"Blood spatter analysis" is not a physics based discipline. The other comment responding to you with the analogy about astrology is good explanation of what is wrong with your reasoning

not so, if i square a number, and get 4, There is no basis in evidence for the claim that the number I squared was 2. it could equally likely have been -2. Science is capable of making no stronger a claim than that.

I think the key challenge to blood spatter analysis is not that there's no way it could be valid, it's that so far, it's based primarily on unsupported assumptions and statements. Those assumptions may well be correct, but the hard physics behind it has not been done yet, it's been just folks saying 'well I'm very clever and this is what I think'.

An internet search shows there is research done, particularly the 'hard physics' behind it..

Is there? Simulating forward sounds doable. Some fluid sprayed from here, with this mass and so on it lands as so. Backwards from a spatter pattern on an object sounds a lot harder, not least because there will be multiple possible answers and heaps of unknown variables.

I mean the Wikipedia article on it basically says as much: https://en.wikipedia.org/wiki/Bloodstain_pattern_analysis

> The validity of bloodstain pattern analysis has been questioned since the 1990s, and more recent studies cast significant doubt on its accuracy. A comprehensive 2009 National Academy of Sciences report concluded that "the uncertainties associated with bloodstain pattern analysis are enormous" and that purported bloodstain pattern experts' opinions are "more subjective than scientific." The report highlighted several incidents of blood spatter analysts overstating their qualifications and questioned the reliability of their methods. In 2021, the largest-to-date study on the accuracy of BPA was published, with results "show[ing] that [BPA conclusions] were often erroneous and often contradicted other analysts."

That's not the same as saying it could _never_ be done properly, but the analysis being done right now is not that, even though it's presented in courts as expert opinion with high certainty.

Blood splatter is still studied. What I think most forensic experts would tell you is they are really trying to compile as much evidence as possible that allows the largest reconstruction of what may have happened. It is not like the movies, or it shouldn’t be, where you find a single finger print and that determines who the killer is.

Everything follows the rule of physics. The existence of some way to do something is a very low bar to clear. There may be some way to determine if there's water underground, but that doesn't mean a dowsing rod can.

The actual current practice of blood spatter analysis is to the physics of blood splatters roughly what astrology is to the physics of the movement of stars and planets.

Could there be an astronomy equivalent for blood spatter analysis? In principle yes, but it doesn't exist yet.

Could the current astrology sometimes shed real light? In some cases yes, just like even an astrologer can tell you something true about where Mercury is likely to be on the sky tomorrow. But the vast majority of the claims of current experts are going to make claims a lot stronger than that.

And just like most astrologers, they will make those claims based on what they want to be true, or what they think you want to be true, not on what the evidence tells them.

Usually solving a PDE “backwards” is not possible. And that is exactly what those people are claiming to do.

IE: from a specific (discrete) distribution of temperatures in, say a length of wire, you cannot infer the distribution some time before.

From my understanding, fingerprint analyses don't have widely-accepted specificity or sensitivity rates either. Those "73% match" figures are not derived from any sound principles.

Breathalyzer tests are incredibly inaccurate and prone to false-positives.

Not saying they have no basis in evidence, but people drastically overestimate their accuracy.

They have an accuracy rate that is pretty good. Sure they have false-positives (eat a gas station pizza, ping positive) but far more likely are false-negatives due to bad air sampling. Folks go to all sorts of extremes to fake them in the car-installed devices e.g. have somebody else blow; blow through a long tube so the sample is just what's in the tube; hold it out the window and let the wind 'blow' into it; put two straws into a half-full drink cup, blow into one and connect the device to the other, and on and on.

The devices have all sorts of countermeasures now including a dash-cam, temperature sensors, humidity sensors etc to try and ensure its actually the right human's breath.

"Pretty good" is completely unacceptable if states will suspend your drivers license for 12 months if you refuse to take the breathalyzer test (many states do this).

Yeah, it's gross that consent to a breathalyzer test is a precondition for even getting a license in the first place.

Are people convicted of DUI based on breathalyzer evidence alone? I would hope that the breathalyzer is just used as a first gate (since it's relatively easy to administer), but then a conviction would require corroboration from a blood test. Then again, with our "justice" system as it is, I wouldn't be surprised if a breathalyzer is enough in some circumstances.

> Are people convicted of DUI based on breathalyzer evidence alone?

In some jurisdictions, absolutely

This depends on the country.

In mine (slovenia, a lot of drunk people here), you can not-sign the agreement with the breathalizer result, and the police will take you to a clinic to do a blood test. Usually breathalizers show a bit less (larger tolerances/errors that the police have to subtract from the measured result), but if you're big/heavy enough, and the nearest clinic is far enough, it might be worth it, since you'll process some of the alcohol in the time to get the blood taken... depending of course if you're on the upper limit to a higher fine or near the lower limit.

> Are people convicted of DUI based on breathalyzer evidence alone?

Yes and no. In the US the DUI process looks like this (it's an interest of mine):

1) Pattern of impaired driving or other reason to justify the stop. This one is ridiculous and of course highly subjective - it includes things like a "sweeping turn" which is essentially not turning into the closest lane of traffic on a turn (think left turn and not turning into the left most lane), tires brushing a line, etc. Then obviously there's speeding, running stop signs, etc. In some states DUI checkpoints are legal where courts have ruled (essentially) that the Fourth Amendment doesn't apply for one reason or another to blanket stops for investigating impaired driving.

2) Some justification to start or continue a criminal investigation beyond the justification for the stop - this is the classic/infamous template: slurred speed, bloodshot/watery eyes, smell of alcohol, etc that you see in literally every single police report for impaired driving.

3) Field sobriety tests (FSTs). These are designed for you to fail and completely ridiculous. In the era of dash and body cams you're essentially going to put on a horrible performance that makes you look intoxicated or at least ridiculous even if you aren't. It's been demonstrated time and time again these tests are subjective and failure prone under ideal controlled conditions with known factors, let alone someone suddenly pulled out of their car on the side of a dark road somewhere...

4) Preliminary breath test (PBT). This is the small, roadside, handheld unit. You're usually going to get this no matter what. Obviously if this reports above the legal BAC limit you're going to get arrested. Depending on a variety of factors (how the officer feels, your FST performance, etc) you can be arrested for impaired driving regardless. This is obviously to account for other drugs that impair driving but of course do not register on an alcohol test. Additionally, you can be under the legal limit and still get arrested for impaired driving for the real/suspected "I had a beer but I also took a bunch of Xanax" type situations. To my knowledge these results are not admissible (or easily defeated) in court.

5) Certified test. When you get down to the police station (or wherever) they're going to have you do a breath test on a "certified" machine that's supposedly tested, calibrated, etc. Interestingly, in most places there are two tests, typically spaced by 20 minutes (or so). Apparently this is to account for the surface/residual alcohol issue. If you swish Listerine around your mouth and blow into a breathalyzer it will max out and tell you you're dead (essentially). Yet obviously none of this alcohol is in your blood. My understanding is for most cases the second reading is emphasized/reported/charged even though it's almost always lower because it eliminates a "residual alcohol" defense and the result is typically far over the legal limit anyway. This test is defined as "scientific" and admissible in court.

Of course in many cases where a breath test is refused or other drugs are suspected they can get a warrant for blood. Typically the barrier here is having a judge on call at 2 AM (or 10 AM, whenever) with a rubber stamp to issue these. That said, most places with DUI checkpoints now will have judges at the ready so more and more a refusal to do FSTs or a PBT at a checkpoint is signing yourself up for an almost instant blood draw.

But, to answer your question there have almost certainly been people convicted on breathalyzer evidence alone. However, "convicted" is a stretch here because to my knowledge there aren't a lot of jury trials for DUI - it's just not really worth it to anyone because the stakes for either side aren't really that high. Besides, in many states the Department of Motor Vehicles or whoever controls licensing has a completely separate administrative process that applies to your driving privilege.

I suspect in many cases where a breathalyzer has been the sole evidence even many (most?) innocent people will plead to "reckless driving" or whatever the prosecution offers - especially because in most places there isn't jail time for a first offense regardless, most states have some kind of hardship/occupational standard in place so that you can still drive for work, school, worship, child care, etc, and as mentioned the DMV process is somewhat separate anyway.

Because of the car-first culture in the US (vast distances, limited/non-existent public transportation, costs of ride sharing, etc) many people just drive with suspended licenses anyway which, to get back on track with tech here on HN, isn't what it used to be. ALPRs (automatic license plate readers) have really changed the game there.

And that is why they should only be for suspicion and any real evidence should be from blood test administered in suitable location verified in lab.

Lots of scandals around DNA evidence as well. It’s not the science itself that’s wrong, but mistakes can be made and were made during collection and in interpretation.

There’s also cases of people who received a transplant who then supposedly have two (or more) different DNAs in their blood.

Wow, that's pretty crazy. I never really thought about how transplants imply two different sets of DNA cohabitating in the same body.

I think the relevant transplant is bone marrow, since that produces Red Blood Cells. Here is an article about it:https://www.nytimes.com/2019/12/07/us/dna-bone-marrow-transp...

Pregnancy presents a similar situation, and fetal microchimerism among parous women is not uncommon. This also includes, supposedly, brain tissue: https://www.science.org/content/article/bearing-sons-can-alt...

A founder I worked with had both a bone marrow transplant and a lung transplant. He named his company 3dna to commemorate having three sets of DNA in his body

It also turns out that chimerism may be a lot more common than we’d thought.

Wasn't there a famous incident where the police assumed they were dealing with a serial killer because identical DNA was found at dozens of crime scenes, and only much much later did they learn it was the DNA of a guy who worked at the DNA analysis lab who didn't always wear gloves like he was supposed to?

Sounds similar to this: https://en.wikipedia.org/wiki/Phantom_of_Heilbronn

No, it was exactly that, and I misremembered some details. :-P

Nowadays DNA is matched by a proprietary software that nobody knows if it's buggy or not. But I've never seen a non buggy software before…

There is some amount of the science itself being inconclusive, as no one has really studied things like "how likely is it for DNA that matches X's to n% precision to be in a location Y given that X has/has not visited that location".

Even discounting intentional placement of evidence, we really don't know how likely it is to find pieces of your DNA in places near to those you frequent - say, in the lobby or elevator or first floor of an apartment building you pass by every day, but have never entered. This is especially important given partial matches, since it's likely thousands of people pass by a building each day that have never made it inside - so the chances of an accidental match increase greatly (while also being guaranteed to match corroborating evidence, such as security cameras seeing you next to that building on the day of).

Conversely, we also don't know how likely it is that you can avoid leaving your DNA in a place you have visited to commit a crime.

Now sure, there are cases like "we found a large smear of blood, all of it containing DNA that matches this suspect 99%, and the suspect has an obvious open wound/scab"; or, the same smear containing DNA that only weakly matches the suspect or the victim or any known eye witness, which is extremly good evidence that someone else was at the scene.

But when one hair or bit of spit is found in an apartment that matches someone who does live around that area, we don't really know if that means anything.

hand-held laser speed measuring

Fire pattern analysis often falsely claimed, from visual analysis alone, that fires were started with an accelerant.

Body language experts... Thankfully I don't think it is used as evidence, but still...

Think again.

Fire investigation was historically plagued by myths like "concrete spalling means the floor was soaked in gasoline before being set on fire". Turns out, concrete just does that whenever it gets very hot, with or without an accelerant.

Ironically, Law and Order SVU has an entire episode focused on that issue.

This was posted years ago on HN and it has always stuck with me.

https://www.newyorker.com/magazine/2009/09/07/trial-by-fire

Jesus Christ. Death penalty advocates always say there are so many checks and that only absolute monsters are executed but this is a case made off animal spirits and the testimony of a fellow prisoner, both of which were later called into serious question. What the fuck.

I think that a lot of people are just bloodthirsty and once they’ve categorized somebody as evil then anything can be done to them. Unbelievable.

> animal spirits

*mineral spirits

But thanks! "Animal spirits" intrigued me, so I read the entire article. A clusterfuck from top to bottom, particularly the bit about the cracked glass patterns... something better explained by thermal shock of cold water from fire-hoses on hot glass, and not the use of BBQ lighter fluid as an accelerant.

Haunting words: "I almost sent a man to die based on theories that were a load of crap."

I used the term "animal spirits" to describe the voodoo that the arson investigator used to justify the conviction (I admit this is confusing given that "mineral spirits" plays a role in the article). The term is often used in economics to describe the fickle and unknowable and seemingly random reasons for market motion. This arson investigation feels just as random.

That was a thing? Was/is there any actual expert involved ever in these claims?

I am more worried about all the claims that one field expert can look at someone and tell if they are drunk, using specific substances or had a head trauma. Doctors can’t do that but I guess… there are “experts.”

Hell yes. A probably-innocent man in Texas executed for murdering his family, based primarily on the evidence of fire analysis which was later shown to be almost entirely bullshit.

https://deathpenaltyinfo.org/policy-issues/innocence/execute...

This is so sad in so many ways. I had to research the topic and this was the first case popping up. Thank you, and... I am still really sad...

> Ultimately, the authorities concluded that Willingham was a man without a conscience whose serial crimes had climaxed, almost inexorably, in murder.

This is what has condemned innocents throughout history to death, torture, and prison. His history is what got him convicted, in my opinion. So many people forget to shield themselves from future indictment by acting "normal" in the present.

> That was a thing? Was/is there any actual expert involved ever in these claims?

Unfortunately, a lot of fire source experts were trained based on a mishmash of folk theories about arson, many of which have been subsequently disproven by scientific testing. There have been some improvements over the last decade or two, but the field is still heavily contaminated by junk science.

Heh, my dad had an old story about how he and his pals got pulled over, his pal was driving. The cop had them all do the thing where you walk heel-toe, touch your nose, etc. His pal driving was unsteady and was arrested, the other two guys were obviously drunk but were passengers, so they were out driving, and my dad who had drunk the most out of all of them was told to drive the two other guys home. When he responded, "I drank more than any of them!" the cop told him, "That's fine, you seem ok, here's my card if you get pulled over, stay safe." Oh, and his pal who was driving was stone-cold sober, but had old knee injuries, so he just walked funny all the time. He was let go at the hospital when the blood test turned up 0.0.

I wonder at what point all those movies are here to legitimize the use of dubious ways of determining the culprit in real-life investigations.

I’ve always been surprised that USA could claim “It’s Al Queida” in the first 6hrs of the Twin Towers falling, and the French police could say “No relation with the wave of terrorism” in the first two hours of Notre Dame burning.

Concrete spalling doesn't require fire at all. Ask any Civil Engineer (I'm not actually Chartered).

I trained as a Civ Eng in Plymouth (Devon, UK) and obviously ended up in IT (22 years as MD of an IT firm). It's quite wet, windy and the air is pretty salty in Plimuff. All of those factors scream: Bad for conc. if you don't allow for them. Also, steel is well known to get quite unhappy in the presence of salty water, if it isn't cared for properly. Concrete cancer is another exciting opportunity to contend with in the face of ... conditions.

Concrete is a marvellous material, it really is but it is a sodding complicated matrix of variously graded (sizes) stones (aggregate) and particular sands bound up in the cement plus some admixtures (stuff added for various reasons). The cement alone is properly complicated - clinker and that. When you mix the stuff up and pour it, it's a chemical reaction that happens and not simply drying. That's why it works underwater - what you are worrying about underwater is avoiding the finer materials being carried off before the stuff sets. In the air, you worry more about temperature effects on setting and wind causing the surface to dry too fast. The reaction is caused by water, so if the surface dries out, the reaction doesn't happen and you get ... spalling later in life.

I hope that the studies quoted in court relating to conc spalling, describe the precise conditions that the stuff was poured in. Care will be taken over the effects of admixtures and the temperatures, weather and other conditions that affect setting and curing of conc. Was gap grading of the agg. a factor perhaps? What is the agg. composition anyway, let alone its size distribution?

I could go on a lot, lot more and I'm not even close to being an expert. I can pour a decent 3-2-1 mix and expect it to do the job at home. My little DIY conc related projects tend to work rather well - my garden is quite challenging topographically.

I hope I'm getting across that concrete is rather complicated. It's not a simple material just as balsa and elm are both "wood" but have very, very different properties.

This report is relevant. If I recall correctly it pointed that some of these analyses are not really reproducible.

https://www.ncjrs.gov/pdffiles1/nij/grants/228091.pdf

handwriting experts?

Fingerprint analysis is rather sketchy, convicting someone based on a tiny part of a print. Also lie detector analysis.

This was my first thought as well. I think penmanship analysis is a candidate.

There are two types of handwriting analysis - "Graphology" and forensic handwriting analysis. Graphology claims to be able to derive personality/psychological traits of the penman, and is just for charlatans. But, forensic handwriting analysis is "real" and useful, for determining if a known-author handwriting sample matches an unknown-author handwriting sample.

Hair analysis is another. Famously, a man was convicted based on hair at the scene that turned out to belong to a dog instead.

https://splinternews.com/the-fbi-convicted-this-man-using-ha...

If only it was limited to the cinema.

https://www.washingtonpost.com/local/crime/fbi-overstated-fo...

Ballistic fingerprinting is almost completely nonsense as used in media. Has some real life use, but limited.

There are multiple types.

1. Capturing a spent casing and comparing to a reference of that firearm. The idea being the primer indentation, and chamber wall tolerances/imperfections should let you match fired case to firearm. This was believed in so much that every firearm sold in the past 20 or so years in NY/MD/?? has required a spent case to be shipped with the gun and a case kept at some crime labs, or the owner is required to provide when registering the gun - the bullshit is that it doesn’t work at all - and not one single solved crime has ever been attributed to this system. Giant waste of money / feel good legislation. There is some correlation to be made… Factory Glocks have fairly unique square firing pins and it’s easy to say a case was or wasn’t fired from an unmodified Glock. Likewise, MP5 platform guns typically have fluted chambers and one can easily see the case marks on a fired case, but neither of these things will help with storing a sample.

2. Muzzle/barrel printing. While this is a LITTLE more scientific, mostly shit. For the most part, you need a really large flaw in a barrel to leave a matchable print on the barrel. You can look a fired bullet and easily tell the rifling. Polygonal (Glocks again), cut, button, hammer forged… but the whole microscope printing of miniature and unique imperfections is a lot more art than science. Again, easy to prove this bullet didn’t / couldn’t come from this gun - but hard to prove it came from this specific gun.

3. Micro stamping entirely bullshit. This is where a California despite overwhelming evidence it doesn’t work is still trying to get firing pins to leave a unique impression on the primer. The people that push for this stuff have no idea how guns work, never have.

Lived in MD. They did away with the spent shell casing law. Turns out they were literally throwing them unorganized into barrels. No way to organize or search through them if there was a need. Just a massive waste of taxpayer money.

fiber analysis is also fake as hell (like saying: these threads came from your carpet, or your shirt).

ballistic forensics only works if the gun is barely fired after the time that the bullets in question are fired, becuase each time you fire a gun it wears down the barrel again, in new ways.

Fingerprint analysis is not based on solid science, nobody knows how common it is for someone to have very similar fingerprints to another person, and nobody knows what the right standard for "points of similarity" is. Fingerprint analysis has been used to convict people of crimes they could not have committed because they were not in the same state or even country, in ways that are provable:

https://en.wikipedia.org/wiki/Brandon_Mayfield

> fiber analysis is also fake as hell (like saying: these threads came from your carpet, or your shirt).

I'm not a forensic technician, but I've watched probably every episode of every true-crime forensic documentary TV show / YouTube channel / podcast / etc that exists; which probably has some weak but non-negligible correlation with having a gestalt impression of what people do and don't use forensic techniques for in practice. (At least in the "solved" cases, since the point of these shows is "how they solved it.")

In every use of "fiber analysis" I ever saw covered, where the "fiber analysis" was actually used to prove something, the thing they're always noticing is "trilobal fibers" — presumably because, at least for some period in recent history, those type of fibers only ever got used by specific manufacturers for specific use-cases (vehicle manufacturers, for car floor matting, IIRC); and weren't part of the composition of anything sold to individuals at retail (except, perhaps, replacement car floor mats.) So "trilobal fibers on the body" could be taken to imply "this person was at some point in a car footwell/trunk."

I don't ever recall any case that made a "fiber analysis" claim other than that particular one. (Maybe once someone claimed something about what proprietary dyes were used on the fibers via GCMS assay — but that's not really "fiber analysis" per se.)

I don't have a link handy, but there was a huge FBI scandle where their experts were essentially calling things a match to a specific person, etc.

But yes, the science is fine if interpreted correctly. The correct phrasing would be exclude or not exclude a suspect. Or for your example, it could be consistent with someone having been in a vehicle. The problem is when the experts say they must have been in a vehicle, or especially a specific individual vehicle.

That seems something that should be criminal. And realistically always asked how many vehicles with this type of material is there around?

The judge should have thrown it out.

Second thing they teach in forensics is that unless I witness the actual event, it is really hard to tie it to a specific person. I can present dozens and dozens of circumstantial evidence which has sufficient weight for a reasonable person to make that inference, but I cannot attest to that.

Judges should do a lot of things. In reality, their quality and knowledge varies greatly.

Any judge worth their salt would prohibit or censor witness testimony making conclusory statements, especially based on circumstantial evidence. This is Evidence 101. Everybody knows the so-called "hearsay" rule, but almost every rule in evidence revolves around one core precept--no evidence is per se conclusive, and the function of testimony of any sort isn't to submit conclusions to the question at issue.

But implying conclusions is exactly what both the defense and prosecutor are working at; they're constantly playing word games, and some judges would certainly be better than others at seeing through the B.S.

Judges are elected in many areas of the US so they're potentially literally some rando in a robe who wants to put "bad guys" in jail, not some master of critical thinking.

Yeah, and the other way you get judges is via appointment. So there's a chance you have a hack that put in because the executive leader likes their politics.

Thank you for the link! Though I would say it highlights a different problem (investigators' bias) than stated. The Spanish police have rejected findings apparently.

> nobody knows how common it is for someone to have very similar fingerprints to another person

Your last example is definitely a good counterexample to this, but I feel in most of cases, the suspects are very few so fingerprints only need to be able to distinguish one of the others, than say, identify a random dude from billions. So it's still useable.

It's like while SHA-1, or even CRC32, is totally incapable for security, it's still perfectly fine to be used to detect if a known file is corrupted (through natural cause, not deliberately altered) or not.

That's like saying if a witness says "he had brown hair, that's all I can say", and only one of "the suspects" had brown hair, that's reason to convict him.

You are misrepresenting the odds of a group of people having an outlier hair color vs a group of people having one which matches sufficiently well to a piece of evidence which excludes the others.

'I remember a brown car' vs "I remember a brown 1976 Ford coupe with worn tires and a broken side window'.

please don't forget all the databases that can search for fingerprints, and all the suspects brought before the detectives, and at that point if they did not have a good enough alibi, or good enough psyche to withstand interrogation, or ...

https://en.wikipedia.org/wiki/Brandon_Mayfield

That's a fair comparison, although I don't know if the numbers work out to a 1976 Ford Coupe or more like a 2005 Honda Civic. But the other thing is, fingerprint analysis is also usually expressed as more like "a 70% chance of being a 2005 Honda Civic with worn tires and a broken side window", the match is always partial (another thing that science doesn't support, those %'s given).

But would a jury think someone having a 2005 Honda Civic with worn tires and a broken side window is alone reason to convict someone? Probably not? Would they think "A 75% match with [fingerprint equivalent]" is alone enough reason to convict someone? Usually. Because they are very misinformed about what fingerprint "science" can and does do.

That is not how criminal convictions (is supposed to) work. You don't have to present evidence that proves that, out of these three people, this one is the most likely killer. You have to prove that, beyond any reasonable doubt, this person has definitely committed the crime in question. If there is some reasonable possibility that some unknown person could have come off the street and committed the crime while leaving fingerprints that happen to match one of the suspects, then that suspect should not be convicted.

>supposed to "supposed to" is doing a lot of work there. People routinely get railroaded in criminal trials because they are too poor to afford good defense or for even sillier reasons like the prosecutor is better looking or more charismatic than the defense attorney.

Absolutely.

But making claims like "fingerprints are good for choosing which of the suspects is more likely to have done it" is harming the situation you describe, not helping. That is, it puts even more onus on the defense attorney to explain how the process is even supposed to work.

The totality of the evidence must prove beyond a reasonable doubt. But not every piece of evidence must provide beyond a reasonable doubt.

If all you have is a finger print--then yea--the possibility someone else with a close match did creates reasonable doubt.

But if the thief was seen in the area at the time and you have a finger print, well that's less reasonable now.

TL;DR; apply Bayesian probability.

I'm not saying you should be convicted by a single fingerprint.

Forensics evidence is almost always circumstantial.

For your example - If everyone wears wool sweaters except one person wearing poly microfibre, what is the inference?

The first rule that is taught in forensics is that every interaction leaves a trace of some sort. The poly microfibre showed up at the scene. How did it get there is now a different type of forensics and where lawyers step in. The prosecutor will insist because the poly microfibre owner was there, while the defense lawyer will insist, there was a party the night before and everyone was rubbing against each other, the poly microfibre wearer and the wool sweater wearers. It can be anyone.

> Fingerprint analysis is not based on solid science, nobody knows how common it is for someone to have very similar fingerprints to another person, and nobody knows what the right standard for "points of similarity" is.

Weird, I mean surely we have enough data to answer these questions with high certainty? Makes you worry that somebody won’t like the answer…

Many things do have a basis in science. The main problem (with almost all of them) is that the results are interpreted in incorrect ways. For example, you can compare hair and fibers just fine. You cannot say it's a match. You can only tell if it excludes or does not exclude someone. Yet many experts would say it's a "match" and the juries believe it's unique to the suspect.

Tracking calls that are over 60 seconds.

Everything is electronic now. There are audit trails. It may take a while to figure out where you were, but they will. So the only advantage of getting off the phone early is to not be there when the cops show up. And the fact of where you were and what phone you used might help them identify you anyway.

You'd be surprised.

a) Drug recognition experts -- commented that on a sibling comment too -- identifying drug usage vs e.g. trauma by sight.

b) blood alcohol levels imply alcohol consumption -- you could actually be walking around with elevated alcohol levels not realizing it due to liver issues+yeast biome/diabetes (https://www.ncbi.nlm.nih.gov/books/NBK513346/)

c) uniqueness of fingerprints -- studies pointing always this is a statistical argument not a unique identifier -- https://www.aaas.org/resources/latent-fingerprint-examinatio...

d) partial DNA match implying perfect match -- partial matches have been used to convict people

e) probably every depiction of mental illness -- there are exceptions but can't say Hollywood does its best there

f) lawyer interaction -- no your lawyer can't just barge in: you have to ask specifically and probably persist on needing a lawyer to consider any further interaction. (And even how you word that is a minefield in the U.S.)

g) talking to the police -- somehow invoking the fifth is something only bad guys do -- it is the other way around. And that is causing issues already.

h) DNA, fingerprints imply you were there. No material can be moved around. And police knows that. (And of course substances too, e.g. you were in a tax/uber after someone exposed to X, you are now exposed to X.)

i) pretty much all of statistics -- this case one would have hoped would be the eye opener (https://forensicstats.org/blog/2018/02/16/misuse-statistics-...)

P.S. j) ... science honestly? I am always dumbfounded with how much lack of basic scientific knowledge plagues courts and in extend society. Courts can not survive with uncertainty: they have to make decisions and stick to them. Science is different.

A lot of these problems come from deference to experts who wear the hat of science. For instance, https://en.wikipedia.org/wiki/R_v_Adams a man was convicted because an expert said the DNA gave 1 in 200 million chance of incorrect match (or something similar), which is incorrect. I don't remember enough details to look it up, but I recall a US case where the prosecution repeatedly used an expert with a history of lying on stand and of course people wrongly spent time in jail for that.

I think a bigger issue here, at least in the US, is prosecutions seems to have a really easy time finding experts, often on the same payroll as the prosecution, who say the things needed to get a conviction and jurors are encouraged to blindly trust that.

That's the whole point of the adversarial system. The prosecution finds experts that state one opinion, the defense finds experts that say a contrary opinion, the juries pick out whose opinions they want to believe. That's the whole point of expert witnesses - they are the only witnesses in the courtroom who are there for their opinions.

The problem is that one side of this equation has a cottage industry of well-funded experts to pick from, but there isn't a cottage industry of well-funded 'bullshit debunkers' to work for the defense.

That's incomplete, to some extent.

The Daubert standard says the judge is a gatekeeper who can rule that a given expert's opinion will not be presented to the jury unless the expert's opinions are relevant, reliable, and based in scientific knowledge.

https://en.wikipedia.org/wiki/Daubert_standard

It's more than that. The judge usually has a good relationship with the prosecution, and the judge is deciding on what the jury is allowed to see and what expert witnesses are allowed to testify as expert witnesses.

>the defense finds experts defense finds nothing because it's a public lawyer and he barely can afford paper for photocopier, so no highly paid experts for you if you are poor

> g) talking to the police -- somehow invoking the fifth is something only bad guys do -- it is the other way around. And that is causing issues already.

The "don't talk to the police" video has been shared enough times on HN that I know I will never do so, at least in the US. The video claims you are likely to incriminate yourself and be charged with something even if you didn't commit the crime the police is investigating!

This presents a summary of all the bullshit science.

https://www.youtube.com/watch?v=ScmJvmzDcG0

You want the book Junk Science and the American Criminal Justice System [1] by Chris Fabricant, the Innocence Project's Director of Strategic Litigation.

The book is an approachable, anecdotal tour of some of the significant issues with each major sub-speciality within forensic science.

The Innocence Project uses DNA testing to prove convicted criminals are actually completely innocent of everything, them undergoes the massive legal battle required to have a chance of going from conclusive evidence of innocence to release in the American Justice System. The are reasonable quibbles with their methods on the margin, but taken as a whole their work is an amazing contribution to society.

Edit: I imagine some people might be skeptical that there's an uphill battle after conclusive evidence of innocence. Take a look at Shinn v Ramirez. Mark Brnovich, the Arizona Solicitor General, successfully convinced the Supreme Court to tell a federal judge they couldn't look at Ramirez's evidence he's innocent. Notably Brnovich said "innocence isn’t enough here" [2][3].

[1] https://www.amazon.com/Science-American-Criminal-Justice-Sys...

[2] https://deathpenalty.org/innocence-isnt-enough-here-arizona-...

[3] https://www.scotusblog.com/case-files/cases/shinn-v-ramirez/

"The Lie Behind the Lie Detector" had a big impact on me [1]. As a kid I made lie detectors (a 9 volt battery, 1M-Ohm resistor, BC108 transistor and buzzer) and got sent home from school for "Interrogating" the other kids. The teacher evidently thought it really worked - even though as an 8 year old I knew it was just an electronic trick.

40 years later the Iraqi government was purchasing thousands of ADE 651 "bomb detectors" [2] - basically a stick - that no doubt caused some poor dudes to get blown to bits by IEDs.

All technology (indistinguishable from magic) has a cult-like aura around it, in that there's the reality of what it does, and a separate set of human beliefs about what it does. Cybersecurity is full of wishful and magical thinking in this regard. I sometimes feel like a kind of James Randi, trying to debunk the certainty people want and project on to technologies.

[1] https://antipolygraph.org/lie-behind-the-lie-detector.pdf

[2] https://www.cnet.com/culture/divining-rod-reborn-as-explosiv...

Thank you. I had not heard of this product before. I want one.

https://en.wikipedia.org/wiki/ADE_651

> According to Iraqi police officer Jasim Hussein, "The vast majority of the people we stop, it's because of their perfume". A fellow officer, Hasan Ouda, commented that "Most people now understand it's what gets them searched, so they don't use as much."

Ulgh, knowing the polygraph is a lie is actually a huge hazard for you.

I once had to take a polygraph test, and I was freaking the fuck out because I knew being nervous will register me as a liar, and I wasn't actually lying at all. I tried my best to stay calm, but I was freaking out during the test, and I actually did fail the polygraph, but passed after a retest.

It's such bullshit. I wish they got rid of this bullshit technology from this earth, because I had so much on the line and I was absolutely miserable before and during the test.

I am sorry you had to go through that, but why would you take it if you knew it was scientifically unsound? I would just say "no, this is scientifically unsound" and refuse to participate. They're going to "detect" whatever they want from my words and punish me accordingly, so I might as well say nothing.

Well, because you don't get a choice, if you don't take it then you don't get what you want (for example, a security clearance or a job), it tends to be a non-negotiable requirement.

You wouldn't get a criminal conviction by refusing to participate, but in other contexts refusal to participate can be (and is) treated the same as failing it.

Ah yes, the good old security clearance polygraph. My friend failed that one 3 times through nervousness. I believe that whole process is just partly to make you nervous and off-balance while they ask you probing questions and partly to signal that you, as an applicant, are willing to ask "how high?" when the government says jump. I did a few clearance processes when I was in the military, ultimately got a TS-SCI, but never took a polygraph; I think because I had a clean-as-a-sheet record since I joined the military a week after my 18th birthday.

It's a compliance test.

If you'll take a polygraph (or engage in any other witchcraft ritual) then you're probably malleable enough to do other dumb things against your better judgement.

In other words you'll act dishonestly to please others or advance yourself. That is to say - it really is a lie detector, just one for seeing how well you can lie to yourself.

Every few years I come across this statement about polygraphs. I want so much to learn about them and how to “beat them.” But every time I look into it, it’s a 300-page book to read or a 4+ hour video commitment.

Why?

Here's the TLDR; polygraph tests really test for stress indictators. If you think they work and you generally stress out when lieing, and you really dwell on the 'oh my gosh, they're going to know I lied, because of the test and I just lied', your stress indicators will be off the chart, and there you go.

If you know they're bunk, and so you can lie without stressing out, then they won't detect stress, especially if you've practiced with a polygraph. But, they usually do some sort of calibration. If you're calm or stressed the whole test, the results are inconclusive. You want to be calm when giving most of your answers, but stressed during the calibration questions where they expect you to be stressed.

The only reason you should submit to a polygraph if is if you want clearance in the US. Or you want to be a on a trashy talk show (eh, someone's gotta be on those, I guess). Anywhere else, stick to your guns and refuse on the basis that they're not reliable and it's a waste of everyone's time; don't be goaded into the 'well if they don't mean anything, why don't you just take it'

Of course, sometimes you might find yourself in a situation where the easiest path to what you want is through a polygraph, and it's easier for me to say don't take it, than for you to refuse.... like, do your best, I guess?

Thank you!!

I vote for a trashy talk show full of HN crowd. Optionally with everyone on polygraphs.

The "real" TLDR (and I am not kidding here!) is that you clinch your anus during every answer. It does something to your heartrate, blood pressure, etc. that makes lies indistinguishable from the truth. Also polygraphers know this and will call you out on it if they think you are doing it. It makes all of your answers register the same and they assume that you will lie on at least one as a baseline (usually something like "have you ever told a lie in your life" or something similar).

how is blood spatter analysis bogus?

Fire forensics.

The ultimate downfall of a society.. when justice system simply becomes just a system, out of convenience.

Heh, I used to watch true crime documentaries pretty religiously at one point.

But the more I read about just how flimsy the science behind some of these forensic techniques was the less comfortable I felt until I pretty much stopped watching altogether.

Good. I am not saying forensic ballistics is just as pseudo-science, but it also needs a hard look to re-validate the deductions and now-accepted methodologies.

> The field has a horrendous track record: More than two dozen people arrested or convicted with bitemark evidence have since been exonerated.

It's probably true that bitemark analysis is ineffective at identifying biters, but I would appreciate it if the full data picture were painted. 2 dozen people out of how many total?

It's like saying "X vaccine has a horrendous track record: more than 50 people have died after receiving it". 50 out of how many? If 200, that is indeed horrendous (25% death rate), but if 50 million, then it's not horrendous (0.0001% death rate). Let me be the judge of what is horrendous or not by giving me full context.

From the article, seems like only a few hundred cases:

“Bitemark analysis has been used only in a small percentage of criminal convictions...At worst, it would require the re-opening and reinvestigation of a few hundred cases.

I’m surprised that this even needed a study, which also makes it an little alarming.

I’m surprised that this even needed a study, which also makes it rather alarming.

Are any implications drawn from these findings from a dentist perspective?

This little eggcorn in the article made me chuckle "little to know" (should be "little to no").

TIL about eggcorns.

    a word or phrase that results from a mishearing or misinterpretation of another, an element of the original being substituted for one that sounds very similar or identical (e.g. tow the line instead of toe the line ).

I have a version of this all the time when writing but it doesn't match that definition. For me, it's more like my writing is transcribing an internal auditory dialogue and my inner voice might be saying 'their' but my transcriber will write 'there'. So, it's not that I don't know what's right ( or write ) but that it comes out wrong without active rereading.

Does anyone else have this?

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