In Utah v. Strieff, the Supreme Court has again weakened Fourth Amendment rights. The Sotomayor and Kagan (joined by Ginsburg) dissents are excellent and important. Sotomayor summarizes the basic issue in the case:

The Court today holds that the discovery of a warrant for an unpaid parking ticket will forgive a police officer’s violation of your Fourth Amendment rights. Do not be soothed by the opinion’s technical language: This case allows the police to stop you on the street, demand your identification, and check it for outstanding traffic warrants—even if you are doing nothing wrong. If the officer discovers a warrant for a fine you forgot to pay, courts will now excuse his illegal stop and will admit into evidence anything he happens to find by searching you after arresting you on the warrant. Because the Fourth Amendment should prohibit, not permit, such misconduct, I dissent.

If outstanding warrants were few and far between and distributed more or less randomly the case would have been wrongly decided but of little practical importance. Outstanding warrants, however, are common and much more common in some communities than others. As I wrote in 2014, in Ferguson, MO a majority of the population had outstanding warrants and not because of high crime:

You don’t get $321 in fines and fees and 3 warrants per household from an about-average crime rate. You get numbers like this from bullshit arrests for jaywalking and constant “low level harassment involving traffic stops, court appearances, high fines, and the threat of jail for failure to pay.”

Sotomayor and Kagan understand all this and the incentives the case now creates for bad policing. Here’s Kagan (who cites some of my work):

…far from a Barney Fife-type mishap, Fackrell’s seizure of Strieff was a calculated decision…As Fackrell testified, checking for outstanding warrants during a stop is the “normal” practice of South Salt Lake City police….And find them they will, given the staggering number of such warrants on the books. …The majority’s misapplication of Brown’s three-part inquiry creates unfortunate incentives for the police— indeed, practically invites them to do what Fackrell did here….Now the officer knows that the stop may well yield admissible evidence: So long as the target is one of the many millions of people in this country with an outstanding arrest warrant, anything the officer finds in a search is fair game for use in a criminal prosecution. The officer’s incentive to violate the Constitution thus increases: From here on, he sees potential advantage in stopping individuals without reasonable suspicion—exactly the temptation the exclusionary rule is supposed to remove.

Sotomayor is at her most scathing in explaining the indignity and serious consequences of an arrest even without a conviction (citations removed for clarity):