Supreme Court

Why a Sensitive Dog Is an Evidence-Impaired Cop's Best Friend


The key isse in Florida v. Harris, which the U.S. Supreme Court heard on Wednesday, is how a judge should determine whether a drug-sniffing dog is reliable enough to provide probable cause for a search. Should he simply accept police assurances that the animal has been properly "trained" or "certified," as the state of Florida and the Obama administration argue? Or should he, as the Florida Supreme Court said, ask for additional evidence, such as the nature of the dog's training and certification, its performance in tests, and its track record in the field? Police and prosecutors are particularly keen to exclude that last category of evidence, insisting, rather counterintuitively, that the record of a dog's hits and misses is irrelevant in evaluating whether its alert indicates a "fair probability" that drugs will be discovered. It is pretty clear why the people seeking to justify dog-triggered searches are afraid of these data: They show that dogs vary widely in their accuracy and often are more likely to be wrong than right.

On Monday I noted the 2011 Chicago Tribune analysis of data from suburban police departments that found vehicle searches justified by a dog's alert failed to turn up drugs or drug paraphernalia 56 percent of the time. A 2006 study by the New South Wales Ombudsman in Australia looked at more than 10,000 searches triggered by dog alerts and discovered that 74 percent of them found no illegal drugs. In other words, as the National Association of Criminal Defense Lawyers (NACDL) and the American Civil Liberties Union (ACLU) note in their Harris brief, "any given alert was almost three times more likely to be a false alert than an accurate one." More-recent data from New South Wales indicate an even higher error rate: 80 percent.

The NACDL and the ACLU also describe a 1984 operation in which Florida state police stopped about 1,330 vehicles at roadblocks and walked dogs around them. If one dog alerted, another was brought in, and vehicles were searched only if both dogs indicated the presence of illegal drugs. That happened 28 times, but those searches yielded just one drug arrest. "Despite the requirement that two dogs alert before a search," the NACDL/ACLU brief notes, "police found illegal narcotics sufficient to justify an arrest in only 4% of cars searched," meaning "the likelihood of a false alert was approximately 96%." With impressive chutzpah, Florida's lawyers claim "this example at most shows a 'false' alert rate under 2%." You see what they did there? Twenty-seven false alerts divided by 1,330 cars equals 2 percent. But the relevant question is not the percentage of vehicle stops that resulted in a false alert; it is the percentage of alerts (in this case, double alerts) that turned out to be false. For purposes of probable cause, we want to know the likelihood that a search triggered by a dog's alert will find drugs. In this case it was 4 percent—not, as Florida's tricky calculation implies, 98 percent. 

What is going on when a dog alerts and no drugs are found? Police and prosecutors want us to believe these are not really false alerts at all: Either the drugs were so cleverly hidden that the cops could not find them, or the dog detected otherwise imperceptible traces left by drugs that were recently in the vehicle or by contact with drug users' hands (which is what the prosecution claimed in Harris). But these explanations are completely unfalsifiable and amount to nothing but self-serving speculation. Furthermore, the "residual odor" excuse weakens rather than strengthens the case for probable cause, since the traces could have been left by someone other than the driver: a passenger, a previous owner, even (as the defendant's lawyers in Harris suggest) a cash-strapped addict who tried to open the vehicle's door while looking for stuff to steal. In addition to residual odors, dogs can be confused by the smells of food, other dogs, and legal chemicals they have been trained to associate with drugs. But perhaps the biggest source of error is the cues that dogs pick up from their handlers, whose expectations can influence the animals' behavior.

A 2011 study led by University of California at Davis neurologist Lisa Lit shows how powerful this effect can be. Lit and her colleagues had 18 handlers walk their police dogs through four rooms where they were told drug or explosive scents might be hidden but where in fact there were no target substances to be found. Each team went through each room twice, for a total of 144 sweeps, and generated 225 false alerts. The alerts were especially likely near markers that the handlers were told indicated the presence of scents—even more likely than at unmarked locations where the researchers had hidden Slim Jims and new tennis balls. "Human more than dog influences affected alert locations," Lit et al. concluded. "This confirms that handler beliefs affect outcomes of scent detection dog deployments."

In a new Huffington Post column, Radley Balko describes a couple of incidents that further illustrate this point:

A couple months ago, a U.S. Customs dog trained in drug detection somehow managed to find a package containing counterfeit passports. While dogs can be trained to detect drugs or explosives, they can't tell a fake passport from the real thing—no dog is that good. Rather, what likely happened is that her handler noticed something suspicious about the package. The dog picked up on her handler's body language, then alerted to please her handler.

Earlier this year, a HuffPost review of a police dog team with the Illinois state police found an instance in which the dog alerted to a trunk full of illegal (untaxed) cigarettes. Even the smartest of police dogs can't determine with a sniff whether a trunk-load of Marlboros was purchased in or out of state. (Not to mention that the dog wasn't trained to detect tobacco.) The dog likely was merely reflecting whatever suspicions its handler had about the driver.

A dog's sensitivity to its handler's cues (whether conscious or subconscious) means that a suspicious cop who wants to search a vehicle (as in Harris) or a home (as in Florida v. Jardines, the other canine case the Supreme Court heard on Wednesday) can essentially get permission from a dog, regardless of what it actually smells. As Balko observes, "drug dogs have become little more than a way of converting…hunches into probable cause." In the case of a home search, the cop will have to take the additional step of obtaining a warrant, but if courts are to treat an alert by a supposedly well-trained dog as the equivalent of probable cause, that is a mere formality. The upshot is that a police officer armed with an obedient dog can search wherever he wants.

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  1. “Despite the requirement that two dogs alert before a search,” the NACDL/ACLU brief notes, “police found illegal narcotics sufficient to justify an arrest in only 4% of cars searched,” meaning “the likelihood of a false alert was approximately 96%.” With impressive chutzpah, Florida’s lawyers claim “this example at most shows a ‘false’ alert rate under 2%.” You see what they did there? Twenty-eight false alerts divided by 1,330 cars equals 2 percent.

    Fascists are getting ballsy.

  2. With impressive chutzpah, Florida’s lawyers claim “this example at most shows a ‘false’ alert rate under 2%.” You see what they did there? Twenty-eight false alerts divided by 1,330 cars equals 2 percent.

    Isn’t this the correct way to measure false positives? I am pretty sure that you wouldn’t want a “false positive” measure that relied on the frequency of true positives.

    The issue isn’t the absolute number of false positives, it is that the likelihood of false positives (2%) is much much larger than the likelihood of a true positive (0.07%) which means a dog’s alert cannot reasonable be considered probable cause.

    1. The percentage of false positives is the percentage of positives that are, well, false, right?

      The issue, of course, isn’t the accuracy of the dogs over the entire universe of tests. Its the accuracy of the dogs over the subset of tests that justify a search.

      I think we’re agreeing, just quibbling over semantics. If you are selling tests, you will naturally talk about the rate of total tests that are false positives. If you are evaluating the accuracy of positive results, you will look at the percentage of positive results that are false. The issue here, of course, is whether positive results from a dog are reliable enough to justify a search, so its the latter that is relevant.

  3. OT:…..itics.html

    Late Super PAC Ad Buy Urges African Americans In Ohio To Vote Republican Because Lincoln Freed The Slaves



    In the final days of the campaign in Ohio, the stops have been pulled out in the scramble to eke out a win. And that means one super PAC calling on African Americans to vote against President Obama because Abraham Lincoln freed the slaves.

    Cable viewers in several markets across the state are being treated to ads by an obscure self-described “alternative conservative” super PAC called the Empower Citizens Network. One of the group’s ads accuses Obama and Democrats of imploding the economy by forcing mortgage companies to lend to “unqualified borrowers” while the Soviet national anthem plays. Another promises welfare recipients that “Republicans can save your money source” by reducing regulations on business.


    No! The horror! Only an anarcho-baby-raper could possibly believe such things!

    1. Y’know all the problems in this country started when they freed the slaves. Then they gave wimmins teh vote and just doubled down on the problems….

      /surely someone believes this…

      1. Well, I certainly don’t believe that.

        Now, letting the Irish in…that’s another story. 🙂

        1. Yes, they’re the ones TRULY in charge of our government and monetary system. Blaming Jews is just a cover.

  4. Until a dog can take the stand, and under examination, explain its thought processes as to why it barked, this is all voodoo bullshit.

    1. Now, son, you go on ahead and keep your mouth shut right there, you hear? You little people better be knowin’ when to be keepin’ yo’ mouths a’locked, got what I mean? Someone could get hurt, eh?

      /Officer Benevolence

    2. WOOF! WOOF!

      that means Old Blue agrees with you.

      Good dog!

      *pats Old Blue on the head*

    3. It’s just a furry version of those magic wands Iraqi police use to “detect” bombs.

    4. Sure, sure and the minute the dog told the truth that he was tired of his asshole handler — BLAM, BLAM, BLAM — that would be one dead dog telling no tales.

  5. Anyone who questions the veracity of dog searches should just be shown the story of Sandra Marie Anderson and her cadaver dog Eagle. Seriously, dogs are intelligent creatures, but why do we continue to entrust them with more evidence than the Salem Witch Trials had?

  6. Based on my armchair legal experience, I would argue that the Supreme Court will accept this notion, because the court (as my observation has it) is that the Court will take no position on trying to plumb the mystery of a trained or improperly trained dog.

    I see this on the same lines as the Kelo decision. Run with me.

    IN the Kelo decision, the Supreme Court refused to consider now or in the future what a ‘comprehensive plan’ was in determining how the properties would be used. While few people talked about this in the wake of Kelo I always thought that it was one of the most important parts of the decision. It made logical sense, but it was the most dangerous and damaging part of the decision. It essentially said, “We trust the right people are in charge, and the court is not in a position to determine if these complex plans these people come up with are viable, because this is outside of the court’s perview. Therefore, if they present a set of spiffy matching binders with plans, we assume that’s good enough, and eminent domain is justified”.

    I see no difference between that and the question as to whether these dogs are well trained enough. If the court has passed the point of questioning whether a trained dog should justify the search in the first place, then the rest of the decision is doomed, because the court can’t logically be expected to determine the training level on a dog-by-dog basis.

    1. I understand the point, but the Court does delve into details when it concerns other parts of the Bill of Rights. For instance, they don’t defer to the people in charge when considering Christmas displays vs. 1st amendment; they’re perfectly happy to count reindeer and Santas against wise men and mangers to strike the perfect balance.

      I don’t expect them to strike the balance perfectly on these complex issues, but they should at least put in place some basic ground rules that curb the worst, most obvious abuses.

  7. Sounds like a plan to me dude. Wow.

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