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Drug dogs and the 4th Amendment

July 9, 2012

Federal Court: 25% Alert rate good enough for drug dogs.

Drug-sniffing dog Ginger and supercop Joe Friday from Dragnet

Drug-sniffing dog Ginger and supercop Joe Friday from Dragnet. Click picture to watch entire episode for free on HULU

A federal court ruled that a search was valid under the 4th Amendment, even though it was based on the “indication” of a drug dog with a 25% alert rate.

That’s 63 false positives out of 85 “Alerts”. And the judge said “Okie-Dokie!” There are many reasons why this is wrong.

Imagine you were one of those false positives; you are most likely poor, or politically unfavored, or a person of color, or just someone the constable does not like for whatever reason. Any number of bad results might come from you being under the police microscope for a couple of hours. This is why restrictions on searches were written into the constitution: it is dangerous for law enforcement to just go fishing around in the lives of people who cross their path.

Search and seizure have always been used as a political tool, for oppression of minorities, or just for harrassment. It’s no good for our political freedoms, it breeds official corruption, and it destroys lives. Our Founding Fathers knew this and created the Fourth Amendment to protect us. Like the Fifth Amendment, it is a “prophylactic rule”.

Fourth Amendment: Search And Seizure

The right of the people to be secure in their persons, houses, papers, and effects, against unreasonable searches and seizures, shall not be violated, and no Warrants shall issue, but upon probable cause, supported by Oath or affirmation, and particularly describing the place to be searched, and the persons or things to be seized.

The Exclusionary Rule

In a long string of cases the Supreme Court ruled that evidence found in violation of the Fourth Amendment would be excluded from the prosecution. This is called The Exclusionary Rule. It carries a high social price tag, but it protects against an even higher social risk of a police state. It is a powerful sanction that keeps police honest.

I’ve mentioned this case to quite a few people and almost all of them said; “Well they found drugs, didn’t they?” Many commenters online said the same thing. But for legal and human-rights reasons it simply is not relevant whether any drugs were found; an illegal search is still excluded. It ignores all the illegal searches where drugs were not found, and if finding drugs erased that legal sanction, police would have a powerful incentive to plant evidence.

Animal analysis results

In the current case the judge ruled that because the dog had passed its certification tests, its alerts constituted valid probable cause, even though it had a dismal record in the field. I’m inclined to think that if the police were lying about the dog’s record, they’d lie in its favor. Whatever the reasons for this disparity, it meant that police had at least a 75% chance of searching whoever the hell they wanted to search.

Animals can be trained to reflect the unconscious directions of their handlers. One famous case of this is Clever Hans, the horse that could supposedly do arithmetic. The owner himself was convinced the horse could do number problems, but it was proved conclusively that the horse was actually just picking up on cues. It is called the “Clever Hans Effect” and I have no difficulty imagining a similar dynamic with drug-sniffing dogs.

Man’s best friend

Drug-sniffing dogs enjoy a high degree of (undeserved) confidence among the public, which like the court is willing to overlook their mistakes. Some of this stems from early presentation of dogs as nearly infallible servants in the War Against Drugs.

Watch the Dragnet episode from 1969, as super-cops Joe Friday and Bill Gannon singlehandedly dream up the idea of using dogs, locate a trainer, find a very special dog, and convince a panel of judges that the dog never makes mistakes. It’s really quite entertaining.

In the episode, one judge says; “How do you know whether the dog is excited by marijuana or a box of dog biscuits? If your dog reverts to its natural state and switches to indicating other things, it blows ‘probable cause’ sky-high!” Moments later the dog finds some marijuana one of the judges had hidden as a second confirmation of the test. Then the dog (who was a real LA Police Department drug-sniffing dog named Ginger, guest-starring in the show) helped arrest a pair of insufferably arrogant dope peddlers (one of whom was played by Dick Van Patten).

As I said, entertaining. (You can imagine Joe Friday’s voice saying this next part if you like.) Unless you are one of the people who fall under that microscope. Then it isn’t funny at all.  You might simply have money in your wallet with drug residue on it (which is to say, almost any money at all).

The False Positive paradox

Then there’s the counterintuitive statistical oddity that even with a mostly-accurate test, a positive result can still mean you have a less-than-even chance of whatever condition (be it drug possession or prostate cancer) is being tested for. The unhappy result of ignoring conditional probability means that a positive result does not mean what we are inclined to think it means. It causes a great deal of misery in both medicine and law, and for the same reason: it sets in motion processes that may do more harm than good. The legal solution to this problem is the exclusionary rule, and it’s one we tamper with at great risk as a society.

I’ve “excluded” discussion of whether any drugs should be legalized; it could be literally any kind of contraband that is at stake. The temptation to prosecute on the basis of evidence found in unrelated searches is a constant danger, and it’s one we must not indulge. Even if it is satisfying to give a dog biscuit to man’s best friend.


  • HULU: Dragnet: Narcotics DR21
  • Dragnet, for those of you beneath a certain age, was a super-popular radio and TV show about Joe Friday, a fictional Los Angeles police detective. Created by actor and producer Jack Webb, it was based on real cases and was known for realistic detail about police life.
  • Florida case challenges use of drug dogs
  • Conditional probability traps include the False Positive Paradox and the Prosecutor’s Fallacy, among others.
  • Combine drug-sniffing dogs with unjust drug-forfeiture laws and you have a formula for corruption. Cops are incentivized to confiscate any cash they find; it is up to you to prove you are carrying it legitimately.
Categories: Uncategorized
  1. July 11, 2012 at 01:51 | #1

    I don’t want to sound like an alarmist, but you can’t turn around these days without witnessing the erosion of one or another right or liberty. I hardly know what to do anymore. It’s demoralizing.

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