The Supreme Court is considering a case that could have a significant impact on how police interact with criminal suspects in high-crime cities such as Baltimore, potentially rewriting the rules for when an officer may detain someone, and whether drugs and guns found during an illegal stop can be used as evidence.
In the latest in a recent series of high-profile Fourth Amendment cases to come before the court, the justices are wrestling with the circumstances under which police may use evidence they find after they make a stop that is subsequently determined to be unconstitutional.
The case, Utah v. Strieff, involves a veteran narcotics detective who stopped a 46-year-old man in 2006 as he left a suspected drug house. The officer had no reason to believe the man had committed a crime, and the state acknowledged the stop was illegal. But the officer discovered the man had an outstanding warrant, arrested him and then found he was carrying methamphetamine.
Civil rights advocates are concerned that a ruling for the police could give law enforcement an incentive to stop more people — particularly in high crime areas — on questionable legal grounds, as fishing expeditions for warrants that would justify a search.
There are some 35,000 outstanding arrest warrants in Baltimore, according to police.
"Those incentives are already skewed the wrong way, and this is a significant reason for the problems that exist in policing not just in Baltimore but around the country," said David Rocah, a senior staff attorney for the ACLU of Maryland.
"Police have far more ability to intervene in our lives — even when we're not engaged in actual criminal conduct — than I think most people suspect," he added.
Those who side with law enforcement take a different view, arguing that officers are confronted by a complex and often murky body of legal precedent that makes it hard for them to do their job even when they are acting in good faith.
That so-called good-faith argument has long been persuasive at the Supreme Court, and has slowly expanded the methods for gathering evidence that prosecutors may use against a suspect.
In a 2011 case that involved a revolver found in a car during a routine traffic stop, the court held police needed to demonstrate "deliberate," "reckless," or "grossly negligent" disregard for the Fourth Amendment before such evidence could be suppressed.
That's as it should be, argues Kent S. Scheidegger, legal director of the Criminal Justice Legal Foundation, a victim's rights group based in Sacramento, Calif.
A finding for the police in Utah v. Strieff, he said, would mean "that people we know are in fact committing crimes will not go free to commit new crimes."
The outcome of the case has become harder to predict after the death in February of Justice Antonin Scalia, a conservative who occasionally sided with defendants in Fourth Amendment cases but who was a strong critic of suppressing evidence, even if it was obtained in a way that was controversial.
And the issue of how the court will now deal with the broader question is even more difficult to ascertain. President Barack Obama's nominee to replace Scalia, federal appeals court Judge Merrick Garland, is generally considered a centrist. But the former federal prosecutor, who led the government investigations of Oklahoma City bomber Timothy McVeigh and Unabomber Theodore Kaczynski, has sometimes sided with conservatives on criminal justice matters, including evidence suppression.
So far, Senate Republicans say they will not hold hearings for Garland, or anyone nominated by Obama to succeed Scalia.
Legal analysts are watching for any sign that the court might take a new tack on the Fourth Amendment, starting with the Strieff case.
"When police cross a line, my experience has overwhelmingly been they didn't cross the line because they didn't care about the line, they crossed the line because they are solving crime and keeping people safe," said Adam Ruther, a former city prosecutor now with the firm Rosenberg Martin Greenberg. "But that's exactly why we have a judiciary."
The interaction at the center of Utah v. Strieff began with an anonymous message left on a South Salt Lake police tip line in 2006 reporting drug activity in a home.
Detective Doug Fackrell watched the house for several hours over the course of a week. He observed people arriving, staying only briefly, and leaving again.
In December, authorities say, Fackrell saw Edward Joseph Strieff Jr. walking out of the home and stopped him in a 7-Eleven parking lot about a block away. The detective asked for his license, discovered the warrant and then searched Strieff. He found methamphetamine, a glass drug pipe, and a small plastic scale with white residue, authorities say.
Police now say Fackrell did not have a reasonable suspicion to stop Strieff in the first place.
Joëlle Anne Moreno, a former federal prosecutor who is now a law professor at Florida International University in Miami, says a decision for police in the Utah case — building on previous precedent over the past several years — could significantly undermine the reasonable suspicion standard that police have used to justify stops for decades.
"You'd have a system where, without any regard for Fourth Amendment rights, cops could stop people and search them and then, if they can get lucky, they could use that evidence against the suspect," she said.
So-called Terry stops, in which police stop a suspect on reasonable suspicion, but don't have probable cause to make an arrest, have been controversial in their own right, including in Baltimore.
Police have long been criticized for the practice, named for the 1968 Supreme Court ruling that upheld it, and also for failing to keep accurate data on how frequently the stops take place and what they yield.
The Supreme Court has taken a varied approach to Fourth Amendment cases over the past several decades, siding with defendants in some areas of the law, and with police in others.
When Baltimore Police gave chase to Freddie Gray last year, for instance, legal experts say, officers were likely on solid legal ground established by the court 15 years earlier. In Illinois v. Wardlow, the court held that a person fleeing an officer without provocation in a high-crime area creates a level of suspicion that justifies a stop.
Gray, 25, died after sustaining a severe spinal cord injury in police custody, sparking riots in the city and reopening a national discussion about police practice in predominantly black neighborhoods.
After the chase, Gray was arrested for carrying a knife, though police and the Baltimore state's attorney are now in dispute about whether possession of such a knife was illegal.
The court ruled against police in a 2012 case involving the use of a GPS tracking device to monitor a suspect. In that instance, the justices found police erred when they installed the tracker on the car of a suspected drug dealer without a valid warrant.
But the court has clearly been chipping away at the "exclusionary rule," an element of Fourth Amendment jurisprudence that restricts the use of evidence found when police stop a pedestrian or a motorist illegally.
In 2009, the court found that an Alabama man was correctly indicted for gun and drug possession even though the officer searched him based on a warrant that had been recalled months earlier, and inadvertently left in a computer system.
Three years earlier the court found that a Detroit man could be charged with possession of drugs and guns found by police during a search that violated the Fourth Amendment's "knock and announce rule," an idea that holds police must provide residents an opportunity to open the door before entering.
A number of observers believe Scalia's absence could lead to a split court in the Utah case. In that circumstance, the Utah state Supreme Court decision — which found that the police had overstepped their authority — would stand, but would not set a binding precedent on the rest of the country.
The Supreme Court heard arguments in the Strieff case on Feb. 22.
Alan Butler, an attorney with the Washington-based Electronic Privacy Information Center, filed a brief in the case arguing that allowing officers to ask for identification absent reasonable suspicion would open a "digital Pandora's box."
A name, Butler wrote in the brief, is no longer just a name, but rather a key to unlock a vast system of public databases containing information on people.
"If officers know that any unlawful stop they engage in could be subsequently permitted by what they find, then they could have a greater incentive to engage in those kinds of stops," Butler said. "We don't want there to be a perverse incentive there."