A warrant? Sure we have a warrant ... Don't we?

The Fourth Amendment allows police officers to conduct searches if they have a warrant based on probable cause, right? But what if the cops only think they have a warrant, but it doesn't actually exist? Well, that's all right, says the Supreme Court. The occasional inadvertent Bill of Rights boo-boo shouldn't stand as an impediment to the enforcement of the law.

The ruling, penned by Chief Justice John Roberts, came in the case of Herring v. United States (PDF). Bennie Dean Herring had driven to the sheriff's department in Coffee County, Alabama, to retrieve something from his impounded truck. Since Herring was apparently a regular acquaintance of local law enforcement, officials ran a check for outstanding warrants. One popped up from neighboring Dale County. Herring was searched, revealing methamphetamine and a gun, which the convicted felon wasn't allowed to possess.

But the warrant had been recalled five months earlier -- an error that was revealed only after Herring's pockets were turned inside out. Its listing in the computer database was a mistake. Police actually had no legal authority to stop Herring. Not surprisingly, his attorney made an issue of the non-warrant.

The matter worked its way up to the highest court, where Roberts and company were unimpressed by a (however unintentional) warrantless search.

"The fact that a Fourth Amendment violation occurred—i.e., that a search or arrest was unreasonable— does not necessarily mean that the exclusionary rule applies," Roberts wrote. Later, he continued, "To trigger the exclusionary rule, police conduct must be sufficiently deliberate that exclusion can meaningfully deter it, and sufficiently culpable that such deterrence is worth the price paid by the justice system."

Petitioner’s claim that police negligence automatically triggers suppression cannot be squared with the principles underlying the exclusionary rule, as they have been explained in our cases. In light of our repeated holdings that the deterrent effect of suppression must be substantial and outweigh any harm to the justice system, e.g., Leon, 468 U. S., at 909–910, we conclude that when police mistakes are the result of negligence such as that described here, rather than systemic error or reckless disregard of constitutional requirements, any marginal deterrence does not “pay its way.” Id., at 907–908, n. 6 (internal quotation marks omitted). In such a case, the criminal should not “go free because the constable has blundered.”

Roberts's reasoning that the exclusionary rule has meaning only so far as it can deter deliberate misconduct is clear, but it seems remarkably naive coming from a jurist with extensive knowledge of the criminal justice system. It assumes that police are always diligent and don't respond to perverse incentives. In this case, the court has created an incentive for police to conduct warrantless searches so long as they can credibly claim that they thought that they had warrants because of poor recordkeeping. That is, the Herring ruling rewards sloppy and inaccurate records that over-report the number of warrants that are in play.

Without even engaging in overt fraud, police can put this ruling to bad use just by using sloppy databases -- especially if they're sloppy in the "right" way.

Roberts was joined in his ruling by Justices Scalia, Kennedy, Thomas and Alito.