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?
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:
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.)
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.
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.
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.
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.
'I remember a brown car' vs "I remember a brown 1976 Ford coupe with worn tires and a broken side window'.
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.
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.
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.
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.
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…
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...
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."
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.
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.
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.
Why?
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?
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.
*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."
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.”
https://deathpenaltyinfo.org/policy-issues/innocence/execute...
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.
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.
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.
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.
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.
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.
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.
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.
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!
https://splinternews.com/the-fbi-convicted-this-man-using-ha...
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/
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.
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.
https://www.washingtonpost.com/local/crime/fbi-overstated-fo...
Reading online I see its still respected lots of places and still taught in forensics. Don't know where that came from.
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.
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.
If someone critiques astrology you don’t reply that “planets follow physics”.
> 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.
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.
IE: from a specific (discrete) distribution of temperatures in, say a length of wire, you cannot infer the distribution some time before.
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.
Not saying they have no basis in evidence, but people drastically overestimate their accuracy.
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.
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.
In some jurisdictions, absolutely
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.
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.