Monday, the Supreme Court issued a 5-3 ruling in Utah v. Streiff that’s raising eyebrows for its implications for Fourth Amendment protections.

In Streiff, the defendant was stopped and questioned by a police officer in a parking lot near a house that an anonymous tipster had claimed was being used to sell drugs. The officer asked the defendant for his identification and called in to a police dispatcher, who told the officer that Streiff had an outstanding warrant out for his arrest for a traffic violation. The officer arrested Streiff and searched him, finding methamphetamine and drug paraphernalia.

The main legal enforcement method for the Fourth Amendment’s prohibition on illegal searches and seizures is the “exclusionary rule,” which stops prosecutors from using any evidence that’s obtained from police activity that is found to violate the Fourth Amendment. The Court has long interpreted this as excluding not just “primary evidence obtained as a direct result of an illegal search or seizure,” but also “evidence later discovered and found to be derivative of an illegality,” as the Court wrote in Segura v. United States, a 1984 case.

In his defense, Streiff argued that the initial stop lacked probable cause, so therefore any evidence seized during the arrest should be excluded. It’s well established that police officers have the authority to search people when they are arresting them (generally referred to as a “search incident to arrest”), in no small part due to the safety issue, to determine if a person has anything that could be used as a weapon against the officer or other officers or inmates at the jail. Streiff’s position was that because it was an unconstitutional investigatory stop when the officer first questioned him, everything that followed after was also illegal and should be excluded.

The Court disagreed, finding that the discovery of a “valid, pre-existing and untainted arrest  warrant” was enough of “an intervening circumstance” to forgive an illegal stop.

Wrote Justice Clarence Thomas for the majority:

[E]ven when there is a Fourth Amendment violation, this exclusionary rule does not apply when the costs of exclusion outweigh its deterrent benefits… for example, the link between the unconstitutional conduct and the discovery of the evidence is too attenuated to justify suppression.

Thomas continues, noting that this “attenuation doctrine” operates to exclude evidence where the police misconduct is “purposeful or flagrant,” not merely negligent:

In stopping Strieff, Officer Fackrell made two good-faith mistakes. First, he had not observed what time Strieff entered the suspected drug house, so he did not know how long Strieff had been there. Officer Fackrell thus lacked a sufficient basis to conclude that Strieff was a short-term visitor who may have been consummating a drug transaction. Second, because he lacked confirmation that Strieff was a shortterm visitor, Officer Fackrell should have asked Strieff whether he would speak with him, instead of demanding that Strieff do so…But these errors in judgment hardly rise to a purposeful or flagrant violation of Strieff ’s Fourth Amendment rights.

While Officer Fackrell’s decision to initiate the stop was mistaken, his conduct thereafter was lawful. The officer’s decision to run the warrant check was a “negligibly burdensome precautio[n]” for officer safety. And Officer Fackrell’s actual search of Strieff was a lawful search incident to arrest. [citations omitted]

Thomas also notes that there was “no indication that this unlawful stop was part of any systemic or recurrent police misconduct,” but rather “an isolated instance of negligence that occurred in connection with a bona fide investigation of a suspected drug house.” Accordingly:

[W]e hold that the evidence discovered on Strieff ’s person was admissible because the unlawful stop was sufficiently attenuated by the preexisting arrest warrant. Although the illegal stop was close in time to Strieff ’s arrest, that consideration is outweighed by two factors supporting the State. The outstanding arrest warrant for Strieff ’s arrest is a critical intervening circumstance that is wholly independent of
the illegal stop. The discovery of that warrant broke the causal chain between the unconstitutional stop and the discovery of evidence by compelling Officer Fackrell to arrest Strieff. And, it is especially significant that there is no evidence that Officer Fackrell’s illegal stop reflected flagrantly unlawful police misconduct.

Justice Sonia Sotomayor issued a scathing dissent against the idea that “a valid warrant will clean up whatever illegal conduct uncovered it,” and challenges the argument that the warrant check was necessary for officer safety, since the officer had stopped Streiff in a public parking lot, without suspecting him of committing any crime, and acknowledged that he did not fear Streiff. “[T]he officer’s sole purpose was to fish for evidence,” Sotomayor writes, distinguishing Streiff’s situation from highway stops, noting the need to ensure safe and responsible drivers:

We allow such checks during legal traffic stops because the legitimacy of a person’s driver’s license has a “close connection to roadway safety.” A warrant check of a pedestrian on a sidewalk, “by contrast, is a measure aimed at ‘detect[ing] evidence of ordinary criminal wrongdoing.’” Surely we would not allow officers to warrant-check random joggers, dog walkers, and lemonade vendors just to ensure they pose no threat to anyone else.

Sotomayor also scoffed at the majority’s position that what happened to Streiff was “isolated” conduct, noting that the states and federal government databases include over 7.8 million outstanding warrants, “the vast majority of which appear to be for minor offenses.”

“Justice Department investigations across the country have illustrated how these astounding numbers of warrants can be used by police to stop people without cause,” she wrote, calling the majority’s opinion a “remarkable proposition,” to say that [t]he mere existence of a warrant not only gives an officer legal cause to arrest and search a person, it also forgives an officer who, with no knowledge of the warrant at all, unlawfully stops that person on a whim or hunch.”

Follow Sarah Rumpf on Twitter: @rumpfshaker.