In anticipation of the Supreme Court’s hearing Florida v. Harris, Penn State visiting assistant lawprof Erica Goldberg has written a pair of  interesting posts at Concurring Opinions. I leave the statistical analysis aspects to Goldberg and anyone else inclined to give it deep thought.  As a lawyer, I decline to engage in anything remotely resembling math unless it involves calculating my legal fee.

The aspect of Goldberg’s posts that I find intriguing is the perpetual and intentional avoidance of quantifying probable cause.

Courts consistently and expressly eschew technical conceptions of probable cause in order to provide police officers with flexibility to exercise their judgment in unfolding situations. In addition, courts focus on whether an officer has a reasonable belief that a suspect has committed or is committing a crime. This metric allows for probable cause to be found in situations where one reasonable officer might assess an 80% likelihood that a suspect is driving drunk, for example, even if another reasonable officer might think there is only a 40% likelihood. We might be tempted to assume the courts require that a reasonable officer be able to believe a crime has been committed by greater than a 50% likelihood, but this has not been made explicit.  All officers must prove to a court assessing a vehicle search is a reasonable ground for belief of guilt.  Further, when a court is making a probable cause determination for itself in determining if a warrant should issue, it must decide only if there is a “fair probability that contraband or evidence of a crime will be found in a particular place.”  What is a fair probability?

Granted, we would be deluding ourselves if we believed that under most circumstances, there could be a meaningful quantification of what constitutes probable cause. Sure, it wouldn’t kill the Supreme to use the ordinary definition of “probable,” as in more likely than not, but that might impair the flexibility of police officers to exercise their judgment, even though that makes probable cause sound particularly arbitrary.

Dogs, however, are entirely different.

In the context of drug detection dogs, where we have actual data on reliability, assigning a numerical value to probable cause — or at least to the maximum false positive percentage upon which an officer can rely — would add much needed clarity to Fourth Amendment law. It also does not undermine police officers’ ability to use their intuition, because the event precipitating a search is not an officer’s informed judgment, but the alert from a dog.

This assumes, of course, that the cops don’t bury the K-9 Officer Fluffy’s screw-ups and maintain legitimate records of every false-positive, false-negative, false-whatever.  It gives rise to some hard numbers, and that makes for some hard law.

At present, doggies are not only furry, friendly and cute as the dickens, but legally untouchable.  If a drug detection dog alerts, a big neon sign pops up screaming probable cause to search, and there’s nothing to be done about it.  The dog only gets it right 3.2% of the time? So what? It’s a dog, and the law loves dogs.

Then the Florida Supreme Court went and screwed it all up by applying basic reason to the myth, as in the expectation that before the Constitution is subject to the whims of a dog (or, for the sake of argument, it’s handler), a sufficient showing of reliability has to be made.  What a bunch of dog haters.

The Supreme Court may have granted cert in Harris to overturn what it considers an unduly burdensome evidentiary requirement on the police. However, if the Florida Supreme Court’s decision is upheld, the Supreme Court should decide numerically what maximum false positive rate can still yield probable cause, given the totality of the circumstances. The Court should not require the introduction of a dog’s false positive rate and then not advise lower courts on what rates are permissible to establish probable cause.  If out of 100 positive alerts to cocaine by a particular dog, the drug is found in only 50 of the cars, the Court should decide whether a police officer may search that car.

For all its efforts to avoid putting a number, a percentage, it may be hard to avoid this time.  The problem, of course, is that should the Supremes fix a percentage for dogs to suffice in establishing probable cause, there is no rational reason why it wouldn’t be applied to probable cause in general.

So what’s wrong with that?  Orin Kerr explains :

[C]ourts should not quantify probable cause because quantification would produce less accurate probable cause determinations. The core problem is that information critical to probable cause is often left out of affidavits in support of warrants: Although affidavits say what techniques police tried that added to cause, they generally leave out both what the police tried that did not add to cause and what techniques the police never tried. Determining probable cause accurately often requires this information, however. By leaving probable cause unquantified, current law enables judges to use their intuition and situation-sense to recognize when missing information is likely important to assessing probable cause. Quantification would lead to less accurate probable cause determinations by disabling those intuitions, creating the false impression that the information provided in the affidavit is the only relevant information. Cognitive biases such as the representativeness heuristic and anchoring effects would allow the government to create the false impression that a low-probability event was actually a high-probability event. To ensure accurate probable cause determinations, then, probable cause should remain unquantified. The result is counterintuitive but true: Knowing less about probable cause improves how the standard is applied.

While I admit that I can’t make any sense of this at all, it doesn’t stop me from disagreeing.  But then, I really don’t like dogs all that much and I like judges using “their intuition and situation-sense” to decide the scope and limits of constitutional rights even less. 

On the bright side, I have no expectation that the Supreme Court will affirm the Florida Supreme Court’s decision in Harris, making all of this a futile academic exercise. Instead, I anticipate a brief decision (perhaps written by Justice Thomas) to the effect that “dogs are cute and if something makes their cute little ears perk up, that’s good enough for us.”  No stats required.