Court rules drug dog barely more accurate than a coin flip is good enough | Hacker News Reader

Court rules drug dog barely more accurate than a coin flip is good enough

washingtonpost.com

165 pointspmiller2149 comments

This article, and in particular the title, is horrible and shows no understanding of the math in play. The facts do not indicate that the dog "is barely more accurate than a coinflip" if 59% of the indications in question turn out to actually have drugs.

Out of 1000 samples the dog is positively indicating for 930 of the (93% of the time) of which 549 are true positives and 381 are false positives. Let's be generous and say that all 70 remaining are true negatives.

If the dog was subbed out for a coin flip we would have a positive indicator 500 times of which 274 would be true positives and 226 would be false positives. We would then have 275 false negatives and 225 true negatives.

So subbing in the dog for a coin catches 275 drug carriers at the expense of an extra 155 false positives. We can argue about whether that is good enough but comparing it to a coinflip makes no sense.

On your quality metric, the best result would come from a two-headed coin that indicated positive 100% of the time. But that seems to me to miss the point rather badly.

Obviously the best quality metric would be 0 false positives and 0 false negatives. A two-headed coin would not achieve that.

You have completely missed the point. Zero error is not achievable. You have to choose to accept either false positives or false negatives. In a free society, false positives are supposed to be considered the greater evil.

I have made no judgement about the relative evilness of false positives vs false negatives. I have merely stated that the dog's performance is dramatically different from that of a fair coin and that making that comparison is a misrepresentation of the facts.

It's not different in the way that matters: both produce a lot of false positives. That makes it a fair comparison despite the fact that some of the details are different.

On your quality metric, the best result would come from a two-tailed coin that indicated positive 0% of the time. But that seems to me to miss the point rather badly.

;-)

Actually, for drug offenses I'd take the two-tailed coin without hesitation. Prohibition doesn't work. Never has. Never will.

Then it sounds like your opinion on the drug war is incorrectly influencing your opinion on issues surrounding the acceptable standards for a probable cause search. While the particular example here is drugs the same questions apply on searches for guns, stolen property or any other contraband.

It's important to keep orthogonal issues separate so you don't cross contaminate and introduce unintended outcomes.

> Then it sounds like your opinion on the drug war is incorrectly influencing your opinion on issues surrounding the acceptable standards for a probable cause search

Well, you set up a straw man, so the rules of logic had already been implicitly suspended in that branch of the conversation.

> the same questions apply on searches for guns, stolen property or any other contraband

No, they don't. Dogs can't generally sniff out guns or distinguish between stolen and non-stolen property, and so dogs can't be used as a pretense in those situations. Using a dog to sniff out stolen property (unless that stolen property happens to be a salami) would make it obvious that the dog is just a pretense.

> It's important to keep orthogonal issues separate

Indeed.

So let's review: the problem is that although dogs can sniff out drugs, unless some very strict protocols are followed, they generally don't sniff out drugs and instead just tell their handler what they want to hear, i.e. that there are drugs (though, of course, the dog has no idea that this is how its actions are being interpreted. All it knows is that if it signals, it gets a pat on the head.)

As a result, dogs are not an effective crime fighting tool, but instead a de facto pretense for doing an end-run around the fourth amendment. The same effect could be produced by other means, e.g. flipping a biased coin, but that would defeat the purpose because that would make the bias obvious, which is exactly the rhetorical point that the original author wanted to make.

Do you really want to disagree with any of that?

Choosing between false positive and false negatives has a lot to do with the consequences. If you miss a drug dealer on a screening test, you missed the chance to catch the bad guy. Depending on the drug and social dynamics, this could be fairly benign (pot) or lethal (cocaine, meth, benzos, opioids). You've also communicated to the bad guy that he can get away with it. Which, given what we know of male behaviour, suggests he will push more drug more brazenly next time.

Or you could just repeal prohibition. Then drug dealers wouldn't be "bad guys" any more and you wouldn't need to catch them.

You have perhaps not autopsied many overdoses.

When i was moving and literally everything i owned and cared about was pulled out of my car at 2am and strewn on the sidewalk in the rain for hours, the "extra 155 false positives" seemed to matter a little more to me than it does to you.

This isn't a clinical study where the stats are everything. This is a real world situation where people are being profiled and it is legalized.

I was not arguing whether dogs with this level of success should be used or not. I was pointing out that the argument made in the essay misrepresented the facts. See my last sentence: "We can argue about whether that is good enough but comparing it to a coinflip makes no sense."

Your point is that it is not comparable from a "I caught more bad guys" standpoint, which is fair.

But I think the other side: to say that a coin flip would punish less innocent people, makes it a fair comparison.

Er, no. A coin flip would punish more innocent people. This is an argument of specificity, not sensitivity. The "screening" test, the "sensitive" test, was when the officer decided to involve Lex.

Not if they've already been screened by the police. IE, if the cops only flip the coin once they would have brought in the dog, then it is no better than a coin flip.

I want to see the ROC curve

So that is after the officers filter of society. Officer picks 100 people to be suspected drug dealers out of N ...

Out of the 100 the officer picks the dog is choosing 93%... but is only right 55%... the dog correlates to the officers choice and both are only right about half the time

The article's whole analysis is fucked up because it ignores the prior probability.

> In U.S. v. Bentley, we see just how damaging the Harris decision really was. Lex, the drug dog that searched Bentley’s car, had a 93 percent alert rate. That is, when Lex was called to search a car, he alerted 93 percent of the time. He was basically a probable cause generator. His success rate was much lower, at 59 percent.

In other words, drugs were found in 55% of cars in which he was brought in.[1] The base rate for drug possession in a car is almost certainly a tiny fraction of that. So between the human judgment to bring in Lex, and Lex's sniffing, the police are able to find drugs at probabilities that are multiples of the base rate. In contrast, if you searched cars based on a coin flip (i.e. randomly), you'd expect to find drugs exactly at the base rate.

[1] Being successful > 50% of the time is pretty much the definition of probable cause.

Indeed you are completely correct.

I wonder if some percentage of Lex's false positives were from vehicles that had drugs in them at one point but not during the search?

Not really. You have conflated a couple things here:

There is some aggregate base rate, which is the percent of a random sample of motorists that are carrying drugs.

Then there is the rate of those who are actually carrying drugs within the a group that the police have pulled over, and suspect are carrying drugs, and have also presumably asserted their rights and refused a consensual search by the police and also do not have some other attribute (such as smell, items visible in plain view) that would provide probable cause.

You argue that "the base rate for drug possession in a car is almost certainly a tiny fraction of that" but in fact the base rate within this much narrower second group should be extremely high in comparison to the general population. And the problem is that searching that group, regardless of what you think of them, is illegal.

In order to make it legal you have to be able to show that you're going to do something specific that will provide probable cause.

Showing that the dog is anything short of a clearly reliable and accurate means of determining that a law is being violated means that the dog is not providing probable cause. A dog that alerts to drugs more 90% of the time when only 60% or so of the population in question has the drugs, has shown results that aren't sufficiently correlated to the data it is supposed to discern.

When that is true it is just a tool for violating laws that prohibit searches.

We need to ask what the ROC curve looks like.

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

> Then there is the rate of those who are actually carrying drugs within the a group that the police have pulled over, and suspect are carrying drugs, and have also presumably asserted their rights and refused a consensual search by the police and also do not have some other attribute (such as smell, items visible in plain view) that would provide probable cause.

Yes, but that hurts your argument rather than helping it. The drug dog does not, by itself have to clear the probable cause hurdle. Rather, the totality of the circumstances has to yield probable cause: https://en.wikipedia.org/wiki/Illinois_v._Gates.

So say the base rate for carrying drugs is 10% in the population. The police, based on their suspicions, pull over a population of people where 40% are carrying illegal drugs. Then, the drug dog comes in, and he's barely better than a coin flip--60% correct. Out of 100 people stopped, he'll correctly identify 24 of the 40 carrying drugs, and incorrectly flag 24 of the 60 not carrying drugs. But overall the process will be right 50% of the time, versus only a 10% probability if you stopped drivers at random. That's probable cause.

But I thought PC couldn't count a officer's inarticulable hunch towards that "totality of the circumstances".

For example, let's say that the dog is not sufficient probable cause. Consider the cases:

1) drug dog indicates + suspect driving erratically

2) drug dog indicates + "I just have a feeling"

Am I correct that 1) might be PC but 2) could not be, no matter how accurate that officer turns out to be in practice?

(In case 2, the dog's finding more drugs than the base rate would not validate its accuracy, as the results are being pre-filtered to have a very different distribution.)

If they're finding drugs at several times the base rate, the officer's suspicions probably aren't an "inarticulate hunch."

The term I used was inarticulable, and if you are unable to articulate something (like to a judge), then that makes it inarticulable -- irrespective of how otherwise grounded it was.

So rationally, the cop's "spidey sense" is indeed evidence. The question I posed to you (and whoever's reading) was whether it counts as legal evidence. And it's my understanding that, no matter how good your spidey sense is, it does not become PC in a legal sense until it is articulable. As Thomas Moore said in A Man for All Seasons:

"The world must construe according to its wits; this court, according to the law."

There's no objective way to determine a base rate here. If you argue there is what methodology are you using?

> [1] Being successful > 50% of the time is pretty much the definition of probable cause.

No, it isn't. 'A common definition is "a reasonable amount of suspicion, supported by circumstances sufficiently strong to justify a prudent and cautious person's belief that certain facts are probably true"' https://en.wikipedia.org/wiki/Probable_cause#cite_note-2

I would argue that if you roll a 100 sided dice, my belief that the result is over 45 is not 'prudent and cautious' but 'optimistic'.

But this is more like a procedure that will let you guess the number that will land > 50% of the time.

Um... not at all. That procedure has 100 different possible guesses. A drug dog only has 2 possible guesses.

edit: Seriously? A downvote for this comment?

Yes, this comment makes no sense. Your selection of a 100 sided dice was obviously just a method to discuss probability. But then you randomly jump to a statement about having 100 possible outcomes? This doesn't have anything to do with the original topic at hand.

I downvoted your comment because the argument you are attempting to make is incoherent. I'm sure that you understand what you are trying to say, but as written your comment does a poor job of expressing that point of view.

> But this is more like a procedure that will let you guess the number that will land > 50% of the time.

If have a procedure for guessing the number rolled on a 100 sided die, you are choosing between 100 different possible guesses. That is nothing like a dog guessing if a person has, or does have drugs (two possible guesses). Attempting to compare the accuracy rates between those two cases is major statistical error.

I thought this difference would be obvious to most readers of HN and was thus surprised to see such a simple statistical error being made. I did not think that verbose explanation would be needed once the error was pointed out.

That's orthoganal the math at play here.

The point of that analogy was to create a situation in which someone is right 55% of the time and see how the language "prudent and cautious" feels in those circumstances.

Whether that means rolling over a certian number on a die, or rolling a specific number on a very strange weighted die is irrelevant.

The "someone is right 55% of the time" scenario is meaningless without considering the base rate. A 100-sided dice has a 55% chance of landing on a number greater than 45. That's the implicit base rate in the hypothetical.

Consider, instead, something like guessing whether someone has had cancer. Only 8.5% of the population has ever had it. If you can guess randomly, you'll be right about 8.5% of the time. If you can guess correctly 55% of the time, you're doing far better than random guessing.

The implicit assumption of the "probable cause" concept is that the base rate is low. I.e. only a small percentage of people have illegal contraband. If a police officer is able to guess that someone is more likely than not to have contraband (i.e. more than 50% correct), then he must be acting on some concrete clues, because he's doing far better than if he just searched people randomly.

A correction for your cancer example.

Now if you take the 50% of people you guessed to be positive for test, only 4.25% will be true positives, indicating 8.5% accuracy rate; if you take the 50% people you guessed to be negative for test, 45.75% will be true negatives, indicating a 91.5% accuracy rate.

But your overall accuracy rate is 50%.

But... you are missing the point yet again. The officer's own judgement is not probable cause without specific indicators (e.g. visual evidence).

"The problem here is that invasive searches based on no more than a government official’s hunch is precisely what the Fourth Amendment is supposed to guard against."

Due to the high alert rate, we actually have a pretty good idea of the base rate of drugs in the situations that this dog is being used in (~50-60%).

The question is whether the dog is actually providing probable cause when the dog has such a high false positive rate.

The assertion of the article is specifically that drug dogs are being used and trained by police in ways that allow them to be be used as "a probable cause generator".

"The Supreme Court originally gave its imprimatur to drug dog sniffs because when used properly, the dog’s finely tuned sense of smell can detect drugs and their absence with incredible precision. But that caveat — when used properly — is critical. If a drug dog isn’t eliminating any innocent people, if it’s validating the suspicions of the police nine out of ten times resulting in searches for which up to half or more of the suspects are innocent, then descriptors such as finely tuned and incredible precision no longer apply."

Thus the base rate that we should be judging the dog against is not the base rate in the general population, but the base rate in the dog's tested sample. We need to incentivize the cultivation of higher levels of accuracy that the dogs are capable of providing.

I agree with you.

But I don't think "prudent and cautious" can quite be boiled down to just a certainty of outcome. Risk/reward plays in a lot. If we take "cautious" to mean a medium degree of risk aversion, then I don't think a cautious person would risk their year's wage on the chance to double it, even with a 55% certainty of success. However, I think they would risk $10 for a 55% chance of getting $20.

So what is at stake? What's the cost of an invasion of privacy?

Because of civil asset forfeiture, the base value is however much cash happens to be in the car, assuming it's enough to be "suspicious" (how just having cash is suspicious, I don't know). Most people don't have large amounts of cash in their car, but those who do have, well, a large amount.

The other quantifiable loss to a car search is time. Based on a quick search, it seems the average hourly wage of americans is $25. Wage isn't really the best evaluation of time, but it's easy. That covers the time wasted, but not the losses due to being late to something. A car search could make someone miss an appointment, or even get fired — or nothing.

I'm going to estimate that the sum of how much the average person stands to lose to asset forfeiture and time is about $100. That's of course not even considering the emotional impact of having your privacy violated, or the potential non-legal consequences of having a car search, say having an affair exposed. I'll try to give a personal answer to that question. How much would someone have to pay me for me to be okay with them tipping of the police that I have drugs in my car? Well since I'd be able to plan for it, missing appointments and asset forfeiture are hardly a concern, but time is. I suppose someone could hire me to stand around and be bored for an hour for $40. I'd let them tip off the cops for say, $600. Since that's how much it would take to make it worth my while and not really just meet the baseline of acceptable, I'll cut off a bit from that, say $60. And then subtract the $40 for my time. Adding in the estimated tangible cost, and that's $600 again.

So let's go with $600 as the cost of an erroneous search. Now we need the value of a successful search.

It's hard to quantify (I'd argue the value is negative because of the questionable value of the war on drugs and the cost of incarceration), but for this purpose, I'll use bounties. A quick search turned up a really bullshit looking page that mentions a county police department offering $1000 cash to anyone who turns in a heroin dealer. While the value to the county is going to be higher than the bounty they offer, I'm going to assume that since this county is offering a bounty in the first place, they value it slightly higher than other municipalities. So let's go with $1000 as the value of catching a drug dealer.

Risking $600 for a 55% chance of $1000 isn't just not cautious, it's a losing game.

So what would I consider cautious? Risking $1000 for a 60% chance of doubling it? I'd characterize that as "cautiously optimistic". 65%? Same. 70%? Sure I'll call that "cautious". Obviously different people will have different ideas of what "cautious" means.

But by my definition, and my value estimates, I'll say the certainty required for probable cause for searching a car with drugs is 85%.

This link was posted: https://news.ycombinator.com/item?id=10024503

The main gist of which is the difference between 'concrete' and 'statistical', which seems to be very different from the way many of use think about 'reasonable'.

The article certainly indicates that you don't need 85% certainty to have probable cause. While officers can have pretty high accuracy rates to their guesses, they need a 'concrete' piece of evidence to point to so they can have probably cause. Drug dogs are being used to create this concrete reason, but this has more to do with their perceived reliability than their actual effectiveness reliability.

My biggest concern with the points that this article raises is that it seems like the dogs are being trained to reliably provide probable cause rather than being trained to provide reliable probable cause.

Ignoring the prior probability invalidates the argument, but it cuts both ways.

Consider a drug sniffing dog at an airport, it sniffs all carry-on bags as people go through the line to be searched. If we find drugs even 10% of the time that the dog whines, it's amazing, because the actual distribution of drugs amongst travelers is minuscule, maybe 0.01 of 1%.

But if the dog is right 55% of the time? This is excellent probable cause for a search.

But by way of contrast, consider a drug-sniffing dog that is only brought in when a human handler suspects a traveller may be carrying drugs. If the handler is very good at their job, and optimizing for success, the handler may themselves have a 55% positive-positive rate. Meaning, 55% of the people they pick are carrying drugs.

Now if the dog whines 55% of the time they are given a suspect that has a 55% chance of carrying drugs, well, that is no better than a coin flip, it's garbage.

And of course, what if the handler is amazing at picking people who might be carrying drugs? For example, what if they have access to warrentless surveillance meta-data and are using the dog as an excuse for parallel reconstruction ("Your honour, I picked this person at random, and the dog whined, so I searched them"). The handler might have a near 100% success rate of picking people carrying drugs.

Now a 55% rate of whining is truly terrible for deciding whether the dog is any good.

>But if the dog is right 55% of the time? This is excellent probable cause for a search.

Going back to the original case, even if we assume that every time the dog doesn't signal there wasn't drugs (so the dog never missed a drug), had the police just searched without bringing in the dog they would've had similar rates. So why isn't the police's 'I think he had drugs, can't give any good reason though' not probable cause if the success rate is nearly 55% when the expected success rate of searching everyone is under 1%?

The numbers indicate that the increased rate is almost entirely within the human's judgment, though. If we assume that none of the cars where the dog didn't alert also didn't contain drugs, then that means that the dog was responsible for an increase from 55% to 59%. It's worse if the dog missed some cars in the 7%.

Now, what's the actual base rate? What proportion of cars on the road contain drugs? I'd wager it's well under 10%. Even if we say it's 10%, that means that the humans are taking the rate from 10% to 55%, and then the dog goes from 55% to 59%.

In other words, the dog is basically useless, except as a tool to make the searches legal. If not for the legal requirement, one could just as easily say that "between the human judgment to bring in the magic 8 ball, and the magic 8 ball itself, the police are able to find drugs at probabilities that are multiples of the base rate."

Apparently police are really good at figuring out whether cars contain drugs, but the law doesn't allow them to act on this directly. And apparently dogs are nearly useless at figuring out whether cars contain drugs, but the law allows their nearly useless indication to be used as the basis for action. This is rather backwards!

Very well said, especially the last paragraph.

One wonders if we have the procedures we do because it gives a thin veneer of scientific respectability over a system that might otherwise appear biased, racist & otherwise distasteful even if it's statistically valuable.

It might even go further. I could see where a system that allows officers to search based only on their own suspicion to actually be biased, racist, and distasteful, while one where they have to call in the dog, and where they believe the dog actually gets results, might be much more evenhanded.

There does seem to be a lot of "this is 'scientific' so it's good" in law enforcement. A lot of forensic techniques are just BS, but are accepted because they're "scientific." Or look at the recent article posted to HN about how polygraphs are nonsense.

Indeed. One is forced to wonder what the solution is to this particular problem. I do not have a good answer.

It's hard for me to come up with an answer, because I want to just say, "Don't search them at all, the War on Drugs is stupid anyway."

Of course, it's the job of the police and the courts to come up with an answer, so we should be able to let them do it. But it seems they can't be trusted to reason about it well.

Well sure but that doesn't really get to the core of the problem because I could just as easily substitute "guns" for "drugs" and all the issues will stay much the same (unless you're also a 2nd amendment purist in which case I might have to struggle to come up with another example.)

Yep, but by then I'm working pretty hard on imagining the alternative scenario and trying to ignore the actual drugs-related scenario and I can't trust myself to think straight about it anymore.

A man that admits his biases! I like it!

Except that they would still only deploy the dogs on cars that meet their bias.

Right, but your biases still get filtered through your thought processes.

If all you need is your own suspicion, it could be easy to let one's bias against purple people run rampant, and search every purple person's car and nobody else's.

If you have to call in a dog which you believe to be effective (even if it may not be) then you may only go to that trouble when you actually have some legitimate suspicion, rather than just going based off your anti-purple racism.

I don't follow you. The "prior probability" isn't just the baseline probability that a randomly chosen car will contain drugs. The drug dog is called in by an officer who believes that the specific car he's pulled over contains drugs.

So the article is correct as written. About four out of every 10 roadside searches conducted on the basis of a dog alert are groundless. This outcome is nearly indistinguishable from a coin flip conducted by the officer who has already flagged the car as a suspect vehicle.

As other people have said, you would actually want to have a ROC chart to see the full characteristics of the dog (you are only considering its specificity at the moment). It will probably look something like this (according to the article, not much better than a coin): https://i.imgur.com/PG3Jacn.png

That would be a fair point if the dog were given the opportunity to make both type-1 and type-2 errors. With the process behind a roadside traffic stop, we actually have no idea how often the dog would generate a false negative. We don't know its specificity in the real-world contexts where it actually matters. We just know that it is very, very sensitive... to something other than the presence of drugs.

The coin flip comparison is bad, but I think the article is saying that the precision is very low (like half) but the recall is possibly high. https://en.wikipedia.org/wiki/Precision_and_recall

I think that's what the article is trying to say too, it just does a very very bad job of it.

Most people have no idea how to use percentages. Most of the population has no hope of understanding what's actually going on with this article.

That becomes scary when you're talking to a doctor about a test that returned a positive result. Does that doctor know how likely it is you actually have what you tested positive for? Are you going to get treatment for this thing?

Gerd Gigerenzer has a nice book about this: http://www.amazon.com/Reckoning-Risk-Learning-Live-Uncertain...

Here's one example about breast cancer testing: http://imgur.com/zO4zkl4

Indeed, I agree with your assessment of the statistical reasoning ability of the general public.

I think that articles like this one, if they were better, could move things (even if just a little bit) in a positive direction by educating the public. Unfortunately when they are as poorly written as this I think they do the exact opposite. Oh well.

Yes, it doesn't make sense to compare to a coin flip. However, I would argue that the article's understanding of the math in play is at least as good as the courts who are deciding these cases.

However my reading is the the 'coin flip' is being used because the dog's accuracy is near false positive rate 50% and they are trying to compare the dog's accuracy vs. a randomly accurate instrument to illustrate the following point to non statisticians:

"If a drug dog isn’t eliminating any innocent people, if it’s validating the suspicions of the police nine out of ten times resulting in searches for which up to half or more of the suspects are innocent, then descriptors such as finely tuned and incredible precision no longer apply."

Keep in mind that the dog isn't putting people in jail. It's assertion is merely being used as evidence for probable cause and a more in depth search. As rayiner notes elsewhere in this thread being right over half the time is generally considered the acceptable standard for probable cause.

> being right over half the time is generally considered the acceptable standard for probable cause.

Care to cite that?

Because that means that in a neighborhood where 51% of the houses contain narcotics, the police have probable cause to search every single house.

See Section IIA of: http://scholarship.law.duke.edu/cgi/viewcontent.cgi?article=.... It explains that probable cause is generally considered a lower standard than preponderance of the evidence (which is a 51% standard).

Actually it sort of directly contradicts you right at the start of that section:

>We do not know exactly what the phrase “probable cause” means, in strict numerical terms. We do, however, know what it does not mean: “probably.” That is, probable cause does not—in the context of Fourth Amendment law—mean that the police must have evidence sufficient to conclude that a suspect is probably guilty or that she probably has evidence of a crime hidden inside her home.

I didn't read the whole paper, but the gist of it seems to being exploring the difference between 'concrete' and 'statistical' and evidence of effects (with a non-conclusive, but general indication that the supreme court leans towards 'concrete' over 'statistical')

Basically if you have a 3 people in a car that contains drugs and thus know 1 of them is guilty, you have probable cause to arrest all of them. (Concrete)

However, if you know that 1/3 of the black people in a certain neighborhood posses drugs, that does not mean you have probably cause to arrest all of them. (Statistical)

Thus my argument is that the low accuracy rate of the dog vs. the baseline of the searched people (which in this case is only known because of the high alert rate) should not allow it to constitute 'concrete' evidence of probable cause.

Additionally, the overall success rate of the dog/officer combination vs. the general population baseline constitutes 'statistical' evidence which is also not sufficient for probable cause.

Generally, my argument would be that allowing the dogs to serve as a final determination of probable cause without requiring high accuracy rates leads to unnecessary harm to the general populace in the form of the unwarranted searched that could be prevented by encouraging effective training and usage.

You're missing the point entirely. We don't care terribly much about the people who eventually go to jail, at least not in isolation.

The problem is innocent people who get searched illegally. Being sent to jail is not the only bad thing which can happen to people; being searched without probable cause is inherently unacceptable without regards to the results of the search.

Being incorrectly sent to jail is much worse than being incorrectly searched.

Therefore the standard of evidence for sending people to jail is higher than the standard of evidence to search people.

Therefore the standard of evidence for probable cause is lower than the standard of evidence for a criminal conviction.

Your statements are correct but you are still missing the point.

Clearly you (and some others) think that the standard for probable cause should be higher than it is. Maybe you are right. Maybe you are not. It's a grey area for sure.

No, I think that training dogs to reliably provide probable cause rather than to reliably find drugs is both stupid and unconstitutional. That has nothing to do with how high the bar for 'probable cause' should be.

No, his statement isn't even correct. The Bill of Rights is not divided into venial and mortal sins, and even if it were, I'd argue that the Fourth Amendment would not fall into the former category.

The Fourth Amendment reads "no Warrants shall issue, but upon probable cause." Why do you think it says this instead of "no Warrants shall issue, but upon cause beyond reasonable doubt." ?

If the tool for determining probable cause is no better than a coin flip -- which is in fact the case (see my other post) -- then the intent of the amendment is being circumvented. It's the whole "probable" thing that's the issue at hand.

You didn't answer my question.

Here's what usually happens at this point in a politically-charged HN thread: I ask a question along the lines of, "Why are you so interested in defending an indefensible aspect of an indefensible war on an abstract noun?", and then I get a nasty note from the admins warning against personal attacks, even though none was intended.

So we'll need to agree to disagree on this one. I suspect we're coming from two very different places.

Our legal system very much distinguishes between venial and mortal sins. You can see that in the very language of the 4th amendment which is why I asked my question. The amendment recognizes that searching someone puts a far smaller burden on them than putting them in jail which is why the standard of proof is very different for those two actions.

My point here has nothing to do with the war on drugs. The same standard applies if law enforcement is searching for drugs or guns or stolen property.

You should ponder this some and then consider changing your point of view so that you can be correct more often in the future.

Being incorrectly sent to jail is much worse than being incorrectly searched.

Not from a Constitutional law standpoint. They are both violations of the subject's civil rights, when the search is based on a pretense, a pretext, or a coin flip.

He is not talking about being worse 'constitutionally'. He is absolutely correct in saying that being sent to jail is worse than being searched. I suspect he is correct positing that is why the standards of evidence for conviction (beyond a reasonable doubt) are higher than for search (probable cause).

He is however missing the point in that he is bringing up a separate standard of evidence that has no bearing on the issue being discussed. Being searched isn't bad just because it can lead to you going to jail.

Perhaps, but my point is that neither standard is being met. If the officer didn't have PC before calling in a dog with the performance history described in the article, then he doesn't have PC afterwards either.

It is not OK to violate one aspect of the Fourth Amendment just because it appears (in someone's opinion) to call for less stringent adherence than other aspects.

You don't know about the remaining 70 are true negatives or not, so you can't use that data for calculation.

If you only consider the 930 cases where there is verification, you do come up to 59% accuracy.

Even using your generous assumption of the 70 cases being true negatives, the dog only come up to 62% accuracy.

Dogs are a 100% proof way to always let the cops search your car. If the court takes that way, they'll have to invent some other legal loophole.

Handler trains their dog to alert on cues such as saying "Good boy" or "Find..." and so on. The dog understands what to do. Alerts and gets a treat or patted on the back.

I am wondering what are statistics of "dog alerted, search performed, but no drugs found", does anyone keep that? It would be interesting as it would reveal the scheme pretty well. (They can of course say, well at some point in the past the car had drugs in it...)

The dog isn't even "as accurate as a coin flip". Given a 93% alert rate, regardless of the subsequent true positive rate, information gain from an alert is approximately zero.

Edit: "accurate as a coin flip" is a bad construction, but I wouldn't exactly expect better from a newspaper. The information gain from a device that activates randomly 50% of the time, 0% of the time, and 100% of the time are all the same, which is to say zero.

Be fair. False positives and false negatives are very different things. A drug dog that finds drugs even sometimes, is still useful.

Imagine if it was bombs they were sniffing for. We'd be happy if they found even one more bomb.

>A drug dog that finds drugs even sometimes, is still useful.

Why even bother with the dog? why not just do random searches? Oh wait, because that would be unconstitutional. The dog exists solely to justify otherwise unconstitutional searches.

Ignoring the fact that false positives don't preclude real positives...it works. People are fond of cute doggies, and often their resentment evaporates.

[citation needed]

False positives only don't preclude real positives if time and resources are not constrained. Time and resources are always constrained.

If it was explosives and a dog got a 93% alert rate irrespective of there being any explosives, then that would be useless and nobody in their right mind would use that dog, as it would have them search 93% of everything.

At that point you might as well give up on faffing about with a sniffer dog and just search the remaining 7%.

Then we should simply search 100% of the bags.

Or maybe just 93%.

If I had a coin that showed heads 93% of the time, I'd think it might be rigged.

IMO, it doesn't seem remotely comparable to a coin flip because the odds aren't 50/50. The dogs are only brought out in certain circumstances when they think a positive might be possible, meaning that lots of people who would be negatives aren't tested and thus not included in that 93%. The cases making up the 93% only consist of people whom they thought may get a positive, meaning the sample is biased to having lots of positives.

I'd compare it to the fact that lots of very hard certification tests actually have fairly high pass-rates (80% or above), simply because people who don't think they could pass don't take the test to begin with - The 80% pass-rate is not representative of the average person's chances of passing the test, nor the difficulty of the test itself.

What's really important is the percentage of those positives which were true positives, vs. false positives. In this case, you would expect the number of positives to be high - The number of true positives vs. false positives would tell you how accurate the dog actually was in the positive case. If this number is also high, then the dog is doing a reasonable job. Of course, to derive a real argument from this, you'd need to know the number of true and false negatives as well, but obviously we don't have that information.

Sure, because a coin is evaluated on its capacity to map to an even distribution of outcomes. Drug possessions, however, are almost surely not an even distribution. If, say, 95% of the people that the dog evaluates have drugs, then raising an alarm 93% of the time is probably pretty good.

In other words: If we wanted a drug dog to be as close as possible to a coin flip, we'd just flip a coin instead.

This isn't being fair. I don't really think the post title is fair either. That 93% isn't comparable to the 50% you're probably thinking for the coin flip, or even the 0/100% mentioned in your edit.

---

93% alert rate means:

93% = false positive + true positive

7% = true negative + false negative

---

We're given "His success rate was much lower, at 59 percent." Assuming that means that 59% are true positives, we know the false positive rate is 34%.

Without data on how many passengers are carrying drugs, we can't say anything about the rest of that result. A plausible world where the drug dog may be valuable is when he unquestionably rules out that 7% of the population that he doesn't alert on, as in false negative = 0.

I believe the reason this number is so high (59%) is that the officer has already used his suspicion to determine filter out most people. This makes the value of the "ruling out" plausibility even more valuable: the drug dog reduces searches compared to trusting the cop.

Ideally, they'd provide the receiver operating characteristics curve [0] or the confusion matrix [1].

[0] https://en.wikipedia.org/wiki/Receiver_operating_characteris... [1] https://en.wikipedia.org/wiki/Confusion_matrix

The real question is whether the dog is better than the officer at guessing who has drugs. If the dog is much better than the officer, it would suggest that a dog 'alert' should be given more weight than the officer's guess. If the dog is no better than the officer, the dog is useless.

I say this because it is possible (and indeed likely) that the officer is also better at guessing who has drugs than a coin toss.

Full Disclosure: I have never used or trafficked contraband, but I do not support random searches or the use of drug dogs in public without a warrant, regardless of their effectiveness.

I have no opinion on the legal and ethical issues, I was commenting only on the classifier. I don't think your first question is appropriately described as "the real question" though, as one of the coolest results of machine learning is that there are techniques for combining multiple bad classifiers [0] in to one really good one.

Even more so, I think that is actually what is happening here. An officer is acting as a tier 1 filter, and then the drug dog is acting as a tier 2 filter, further reducing the number of false positives, which in a "legal and ethical" sense, we generally feel are worse than false negatives.

[0] https://en.wikipedia.org/wiki/Ensemble_learning

>" An officer is acting as a tier 1 filter, and then the drug dog is acting as a tier 2 filter, further reducing the number of false positives, which in a "legal and ethical" sense, we generally feel are worse than false negatives."

If the officer is acting as a filter, then it seems to me like this is a search, and not allowable, because it would be subject to all the usual objections to random searches. You might be right, but if that is the only way for these searches to be better than the officer's guesses, it seems that drug dogs would not be allowed to 'sniff' in public without warrants.

If the dog is much better than the officer, it would suggest that a dog 'alert' should be given more weight than the officer's guess. If the dog is no better than the officer, the dog is useless.

A very big problem is that drug dogs will alert when the handler gives it subtle clues. This is done to get probable cause for a search when there is nothing more than an officer's hunch or just a desire to hassle a particular individual.

This is something I see claimed a lot. I'd be very interested in any information you have about this. I find it very unlikely this kind of training is part of the official training, so I'm imagining it's some kind of unintentional conditioning? Or is it done on purpose by the officers?

This is covered in the article, and it's quite straightforward. The handler was giving the dog treats for alerting, rather than giving treats for finding drugs.

The primary trouble I see is that there is no penalty for re-training dogs like this.

The article only discusses that the handler gives the dog treats for alerting, it doesn't go into the motivations about that, whether they're because the officers aren't considering the Pavlovian conditioning involved and are accidentally reinforcing such behavior or if it's intentional.

Does the motivation matter when we're talking about whether it establishes sufficient justification for searching someone's car? After a clear flaw is pointed out, a response of "We didn't mean to ruin the statistical power of this test" wouldn't do much to restore my confidence in its results.

I was specifically responding to this comment

>This is done to get probable cause for a search when there is nothing more than an officer's hunch or just a desire to hassle a particular individual.

that claims that this is done purposefully. That's what I was wondering about, not the overall efficacy of drug dogs.

You can watch this 6 minute video of a stop, I've linked to where the officer was caught triggering the search

https://youtu.be/w-WMn_zHCVo?t=3m35s

It happens.

Thank you. It is kind of the videographer's assertion that "Check here" is a command to trigger instead of just a command to check there, however, isn't it?

Yes but no drugs were found and the 'scratching at window' was the trigger for search. As the op article indicated - four legged search warrants.

That doesn't really address my comment. It's still just an assertion that that is an intentional trigger. The op article similarly makes this assertion but there is no supporting evidence that I saw.

It's not intentional, but it's a real thing:

http://www.ucdmc.ucdavis.edu/welcome/features/2010-2011/02/2...

So it's less an issue of police officers intentionally triggering things in order to harass individuals like the original commenter said and more of unintentional training. Thank you for the link!

One can call it plausible deniability.

There are many examples that have been caught on camera, I see that another commenter posted a link to one of them on this thread.

When you see things like the handler returning to a previously cleared spot and indicating that the dog should check it again; three or four times until the dog alerts, you can assume that the handler has a severe short term memory problem and he just forgot that the dog had previously checked the area and failed to alert. I think it's more indicative of the officer hinting to the dog that "this is where I want you to alert" and their training reinforces the idea that if the dog does what's expected, there will be a treat.

That's why I was asking about if there was any information about this, or any studies/investigations done, since people can go back and forth forever with "Well, did they already check that part? Is it intentional? Was the dog triggered?" Etc.. etc... It definitely seems like an area ripe for investigation, I just haven't seen any.

Antidotial evidence: I have never had a dog that didn't know my moods, fears, apprehensions, etc.? I don't think being called "Man's best friend" is a worn out cliche?

My last dog picked up on so many of my personality traits/tells-- I felt quilty.

(My cat--whole nother story.)

Very true, I guess my question is about the intentionality of it. I doubt you intentionally trained your dog to respond to your moods, but he/she did it anyway. The claim here is that officers are doing this intentionally in order to get around the law of probable cause. I'm interested in cases where this has been shown to happen.

The dog has low precision and high recall. The dogs are capable of high precision and high recall, but aren't being trained to do that because other incentives are at play.

I found it impressive that the dog that alerts 93% of the time was correct 40% of the time. That means the police are doing what seems like a good job of identifying targets that actually have drugs. With those kind of odds, you'd probably want to take a closer look at everyone just to make sure you aren't letting people with drugs get away (false negatives).

Erm, let's say 10% of the people on whom drug dogs are called have drugs.

Then for 1000 stopped, you'll have

0.59 * 0.1 * 1000 = 59 true positives and ...

0.34 * 0.9 * 1000 = 306 false positives.

That's pretty terrible.

Your math is wrong.

The article indicates that of all the people the dog indicated had drugs 59% of them actually did. So for 1000 people whom drug dogs are called on

930 the dog indicated had drugs. Of those 549 were correct and 381 were false positives.

It's in the article. The 93% in that study includes a 59% true positive (of 93%, presumably) success rate. We can't know how many true or false negatives there are because those searches aren't actually carried out, so out of every hundred cars stopped for a dogsniff, 55% (59% of 93%) are found to be carrying drugs.

More worryingly, that also means that out of every hundred cars stopped, 38 are wastefully searched by police (after getting probable cause from the positive dog alert) without finding drugs. From the article, a search takes about 45 minutes and carries a bunch of other risks for occupants of suspected cars (e.g. civil forfeiture, overenthusiastically trigger-happy LEOs), so this is pretty bad situation, not just in wasted time and cost, for both the car occupants and the police force.

One slightly positive thing I'll take from this: Over 50% of cars that are dogged have drugs, and I sincerely doubt that over 50% of cars (on average) have drugs, so in this particular study it appears that police have a better than random chance of guessing which cars have drugs. It's not a very positive thing though, because civilized countries that operate under the rule of law cannot permit law enforcement to operate on guesswork. This is underlined by the fact that the article mentions that the false positive rate rose to something like 80% for latino drivers.

Sorry - I edited my post multiple times after posting it to clean it up and increase quality. Some of your response (especially the first paragraph) is now confusing. That was my fault.

I agree with you mostly - especially on the discussion of what "probable cause" should be defined as and what constitutes a "random" search, as just an example of some of the ethical issues of interest here. That is a debate to have and even one I think this community is well equipped to discuss, but it was not something I was trying to comment on.

I was only making the point that it wasn't fair to jump on the 93% as though it was representative of the problem. I am not taking any ethical or defensive position of drug dogs here.

It's plausible that the 7% is all true negatives. It's also plausible that the 7% is carrying drugs at the same rate as the 93%, and the drug dog is doing nothing at all. If that is the case, then flipping a biased coin would be just as effective as the drug dog.

I think the coin-flip analogy comes from the idea that once an officer thought you had drugs, he/she was about 55% right (not accounting for false negatives). The dog alerted most of the time, thus allowing for search to confirm or deny the suspicions. Thus the dog gave no real information and the officer was the coin, but the reporter conflated these success rates.

I am not a professional dog trainer, meaning I do not have a CPDT certification nor do people pay me. However, I have extensive experience training dogs at a local dog shelter (minimum two hours/week) in a specific training atmosphere, and I have a fair amount of experience with "nose works" which is somewhat related to "drug sniffing dogs" (nose works is where a drug dog might start, for instance). In other words, if software didn't pay so darned well I could go jump through the hoops and hang out my dog trainer shingle. I also hang out with a lot of trainers who are certified and paid for their work.

With my (albeit weak) credentials out of the way, my quasi-professional opinion is that drug dogs are the polygraph test of the drug war. I've watched bomb and drug dogs at work, and much like a polygraph, I think you can read anything you want into the dog's actions. And unless you're 100% consistent (and even pros aren't), the dog might mis-read the handler. There are retired women who devote way too much time to the "nose works" sport with their dog(s), and in competition even those dogs get it wrong a fair percentage of the time.

For bomb sniffing and sniffing for bodies after a disaster, that's fine. Dog says there's explosives, turns out Fido was wrong, no biggie. A few folks got unnecessarily riled up, but no other harm done. Dog said it found a body, but there's nothing but rubble? Meh, did some digging we didn't have to do, but otherwise little harm done (though we could have been digging for a real person).

Sniffing for drugs? False positives have a greater impact. And just because the dog hit, and there were drugs, doesn't mean the dog was right. Correlation and causation and all that, I suppose. Anyway, I'm explaining this poorly, but I hope the gist gets across.

TLDR: I spend a lot of time around dogs trying to teach them things. They might be more reliable than a polygraph, but I'm not willing to ruin people's day or lives over the word of a dog.

The article says:

> In 2013, the Supreme Court made things worse in Florida v. Harris. In that case, the court unanimously ruled that mere certification of a drug dog was enough to establish a presumption that a drug dog is reliable, regardless of the reputation of the certifying organization, regardless of whether that organization understands and appreciates the importance of training dogs to ignore their handlers’ suspicions, and regardless of the dog’s performance in the real world.

But the decision in Florida v. Harris says:

> A defendant, however, must have an opportunity to challenge such evidence of a dog's reliability, whether by cross-examining the testifying officer or by introducing his own fact or expert witnesses. The defendant, for example, may contest the adequacy of a certification or training program, perhaps asserting that its standards are too lax or its methods faulty.

...

> In short, a probable-cause hearing focusing on a dog's alert should proceed much like any other. The court should allow the parties to make their best case, consistent with the usual rules of criminal procedure. And the court should then evaluate the proffered evidence to decide what all the circumstances demonstrate. If the State has produced proof from controlled [7] settings that a dog performs reliably in detecting drugs, and the defendant has not contested that showing, then the court should find probable cause. If, in contrast, the defendant has challenged the State's case (by disputing the reliability of the dog overall or of a particular alert), then the court should weigh the competing evidence.

...

> Harris, as also noted above, declined to challenge in the trial court any aspect of Aldo's training. See supra, at 3. To be sure, Harris's briefs in this Court raise questions about that training's adequacy — for example, whether the programs simulated sufficiently diverse environments and whether they used enough blind testing (in which the handler does not know the location of drugs and so cannot cue the dog). See Brief for Respondent 57-58. Similarly, Harris here queries just how well Aldo performed in controlled testing. See id., at 58. But Harris never voiced those doubts in the trial court, and cannot do so for the first time here.

So what that supreme court case actually* says is that the validity of a drug-sniffing dog as probable cause for a search can be challenged in court, but the challenge must be made in trial court rather than on appeal.

The article says that certification establishes a presumption of reliability. That means that certification can shift the burden of proof to the defendant. In that case, Bentley would have to prove to the jury that the dog is unreliable. It's correct.

It seems Bentley's trial counsel erred by not presenting evidence that the dog was unreliable, and hence did not meet Bentley's burden.

[Edit: clarity]

Not the first time, nor is this the worst offense perpetuated by drug dogs. A town in New Mexico used one drug dog with an expired certification, "Leo", in order to justify invasive anal probes on two men--neither of whom had drugs. To add insult to injury, both men were later billed by the hospitals for this non-consenting search.

Timothy Young, 2012: http://krqe.com/2014/07/28/nm-driver-tells-story-of-sheriffs...

David Eckert, 2013: http://www.dailykos.com/story/2013/11/05/1253274/-Absolutely...

Both cases were eventually settled, leading to Young receiving a $900,000 settlement and Eckert receiving $1.6 million: http://articles.latimes.com/2014/jan/16/nation/la-na-nn-new-...

These two cases are an absolutely horrifying violation of human rights and I'm really glad to see drug dogs being taken to task as part of what led to both of these men being violated.

This is hardly news. Until we put in real consequences for both police and judges who intentionally misbehave or oftentimes fail at their job, none of this will change.

Here's an idea: penalize the cop for every false positive. Docking pay seems to be the best idea here. I guarantee drug dogs' accuracies will go up nationwide within weeks (or however long it takes to retrain dogs and their masters). Every 5 or 10 false positives, dock the cop extra pay or reprimand him. Problem solved.

Here's another idea: hold judges accountable for police actions in the courtroom. If the police lie on the stand, and it's shown that the judge had "probable cause" the judge should be fired. The collusion problem between police and judges, what the article is referring to tough maybe not explicitly, will go away as well. Problem solved.

tl;dr: The only way to keep the police in check is to make them suffer real consequences for fucking up. This will never happen in the US because the citizens here have no idea about the atrocities the police are comitting and the police prefer to keep it that way.

To be clear, what this appellate court and the trial court were asked to consider are different questions.

Trial courts find facts. For example, "this guy shot that guy". Mostly these are considered by a jury, but in preliminary things such as Bentley's probable cause hearing, the trial court judge can act as a fact-finder.

Appellate courts interpret laws. For example, strip searching a middle school student for pain medication is an "unreasonble" search under the Fourth Amendment.

Lex is demonstrably inaccurate. Bentley argued in appellate court that Lex's alert is insufficient to support probable cause under any circumstances--i.e., a "matter of law". Bentley did not argue in trial court that Lex's alert was unreliable in his situation--i.e., a "matter of fact".

The ruling simply reject's Bentley's argument, but preserves future defendant's rights to make the latter argument.

AdaBoost is an algorithm for taking weak classifiers (performing only slightly better than random chance) and boosting/weighing them such that together they are a strong classifier. https://en.wikipedia.org/wiki/AdaBoost

To play the devil's advocate, if the dog alerting to drugs is only one of the classifiers in play (others being the suspects look/act under the influence), and if it's weighed correctly in an officer's mind, it is a key part of the strong classifier.

Humans don't properly implement AdaBoost on their heads.

If a dog alerts an officer, confirmation bias will cause the officer to think "now that I look at him closely, he sure seems to be acting strange..."

For bad implementations of adaptive boosting, weak information can be worse than no information.

If we could convince the suspects to repeatedly drive by the same officer and dog n number of times so they could be pulled over and a trial run, that might just work.

But if you are going to use that reasoning, then you need to remove the dog from the equation and only judge the officers on their actual success rate, utilizing any method at their disposal. What should this rate be? 50%? Any officer who falls below that rate should be forced to get approval from another officer with a higher success rate? They can then choose to use dogs to supplement certain officer's accuracy without giving them incentive to train the dogs to be "probable cause generators".

Using a weak classifier to serve as the basis for getting around a constitutional right is pretty messed up.

> Using a weak classifier to serve as the basis for getting around a constitutional right is pretty messed up.

I was playing the devil's advocate, in case you missed that part, and my point was that a classifier being weak does not necessarily make it bad, as evidenced by AdaBoost.

At that point why not just have officers approach a suspects car with a box with a button and two lights, press the button and if the light turns green, there is "reasonable suspicion"? Just have the light turn green everytime and they can always search you and F the 4th Amendment.

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

I wonder if we could use bees instead then, as there seemed to be some interesting research on training them to detect drugs and presumably they wouldn't be biased by human behaviour especially.

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

Alternatively are there any portable mass spectrometers now?

Surely a portable mass spec would be an actual search?

You'd hope so, especially since the court ruled that pointing thermal imaging cameras at your house from the street constitutes a search.

Another thing Bees were being used to detect was explosive, but researchers discovered that bees detected the impurities in explosives. If you gave the bees pure samples of explosive they didn't do very well.

Professor Jackie Akhavan (Professor of Explosive Chemistry) mentioned this on the BBC programme "The Life Scientific", where a scientist talks to other scientists about their work. It's for a general audience so nothing particularly technical, but still interesting.

Cheers, I'll see if I can grab that.

Sorry! I forget to include the link. Here's that specific episode: http://www.bbc.co.uk/programmes/b04jk360

> Jackie Akhavan, Professor of Explosive Chemistry, tells Jim al-Khalili all about the science of explosives. She explains exactly what explosives are and how to make them safer to handle.

> She started by working on how to make fireworks safer and has been involved in research with bees to see whether they can be used smell different types of explosives. Her current project involves testing the rocket fuel that will be used in Bloodhound, the British designed and built supersonic car that aims to reach a speed of 1,000mph.

> Her work involves finding out how to best detect explosives in airports and elsewhere, teaching security professionals how to differentiate between false alarms and the real thing. She also works on explosives used in warfare and discusses the ethical issues involved.

All this doesn't matter until the root cause is fixed. Police will find a way. The root cause* is mentioned in the article, property seizure laws. As long as there is monetary incentive Police will be compelled to violate the constitution.

* The real root cause is the criminalization of recreational drugs. But ending Prohibition is basically a non-starter.

Hm. What would be the probable cause level required for a search of a politician's records, phone calls, and bank accounts for evidence of bribery. We could probably use big data to establish patterns which are indicative of bribe-taking that would be demonstrably more reliable than 50%.

This headline is pretty terrible.

Keep in mind when looking at these statics that the number for this dog is not based on a random sample. Therefor it is impossible to actually gage the dog's accuracy from these numbers, since we don't know the ration of false:true negatives, only the number of false:true positives. The ratios could be identical, which would make the dog's alerting behavior random. There could even be a higher ratio of false:true negatives, which would make the dog worse than random.

The only meaningful number is the 93% ratio which basically means that the dog is very close to being a 'probably cause generator' as mentioned in the article.

So drug dogs become a kind of police "search anything" power totem.

(This as opposed to the "kill anything" power totem that is the cops brain and tongue via I thought he had a gun or I thought my life was in danger; or the "break into people's home and terrorize them" power totem of the knock-less warrant; or the "track anyone, listen to anyone" power totem of the Patriot Act, etc. at the federal level.)

You forgot "he reached for my gun" or in the case of Zachary Hammond, "he tried to kill me by ramming me with his car" (by pulling into a parking spot).

Before the US revolutionary war they were called "General Warrants" and allowed British soldiers to search and seize as they pleased.

Merits and repercussions of drug prohibition aside, the fact that the dogs can signal a false positive on command seems unsettling.

Not only is this an important civil rights issue, but it's a safety issue too. If the dog is used as a proxy for the bias/hunch of the officer, rather than objectively, then adversaries can use that to their advantage, e.g. to divert resources away from a real threat.

Here's the full text of the case for those interested: https://casetext.com/case/united-states-v-bentley-13

Statistics should be a high school course.

Upvoted because drugs are good.

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