BALTIMORE, MD - APRIL 28: Maryland state troopers stand guard near a CVS pharmacy that was burned to the ground yesterday during rioting after the funeral of Freddie Gray, on April 28, 2015 in Baltimore, Maryland. Gray, 25, was arrested for possessing a switch blade knife April 12 outside the Gilmor Houses housing project on Baltimore's west side. According to his attorney, Gray died a week later in the hospital from a severe spinal cord injury he received while in police custody. (Photo by Andrew Burton/Getty Images) Maryland state troopers stand guard near a CVS pharmacy that was burned to the ground yesterday during rioting after the funeral of Freddie Gray, on April 28, 2015 in Baltimore, Maryland. Gray, 25, was arrested for possessing a switch blade knife April 12 outside the Gilmor Houses housing project on Baltimore's west side. According to his attorney, Gray died a week later in the hospital from a severe spinal cord injury he received while in police custody. (Photo by Andrew Burton/Getty Images)

BALTIMORE — When police spotted Freddie Gray and he took off running through his Baltimore neighborhood, officers made a split-second decision to give chase, setting in motion his death in custody and rioting in the streets.

Fleeing from police is not, by itself, illegal in America, and the U.S. Supreme Court has made clear that in safe neighborhoods, people not suspected of criminal activity can ignore a police officer who approaches them, even to the point of walking away.

But courts have set a different standard for places where street crime is common, ruling that police can chase, stop and frisk people if their location contributes to a suspicion of criminal activity.

This double standard is having a major impact as more black men die in encounters with police around the country. Many have been shot or tackled while trying to flee. The court rulings justifying police chases in high-crime areas where many African-Americans live are contributing to a dangerous divide between police and citizens, said Ezekiel Edwards, director of the Criminal Law Reform Project at the American Civil Liberties Union.

“Folks who are going to be the most intimidated or scared of the police are the same people in places where the Supreme Court has said, ‘if you run from police, that’s suspicion,'” he said.

Edwards is among the legal experts who say unprovoked flight, on its own, shouldn’t justify a chase: “If you can walk away, you can run away. It shouldn’t matter the speed at which you move away.”

There are limits to this leeway: The Supreme Court and lower courts have repeatedly required police to have some justification for stopping or questioning someone in a public place. But several legal experts say that because he was standing in a drug-infested area, Gray’s decision to bolt on April 12 may have justified the decision by four bicycle-riding officers to pursue and detain him.

“If the police show up and someone takes off running, that is enough to give rise to suspicion by police,” said Joelle Moreno, a former federal prosecutor who is now associate dean of the Florida International University law school. “Running is enough for a preliminary level of suspicion.”

Gray, 25, was pinned to a sidewalk, handcuffed and hoisted into a police van where he was put in leg irons after Baltimore officers said he made eye contact with them and ran. Somewhere along the way, he suffered a fatal spinal injury, and the six officers involved were suspended with pay amid a criminal investigation. Many in Baltimore are skeptical, questioning why officers chased after him to begin with.

Baltimore police initially said the officers acted because they believed Gray was involved in some kind of criminal activity. Later that day, an officer swore in a court document that he had found a knife clipped to the inside of Gray’s pocket, and asked that he be charged with carrying a switchblade. A summons was produced, but Gray was in a coma by then, and died a week later.

“The officers made eye contact and he ran. That’s part of the question we have to dig into, if there’s more than just running. There is no law against running,” Baltimore police commissioner Anthony Batts said.

A Gray family lawyer put it more plainly: “Felony running doesn’t exist and you can’t arrest someone for looking you in the eye,” attorney Billy Murphy said.

Even without a law however, officers can make so-called “good arrests” of runners that will hold up in court because of two legal requirements that have evolved from court rulings on police powers to stop people. The first is higher — probable cause — which requires that police have “sufficiently trustworthy facts” to believe the person was or will be involved in a crime.

The second is lower — reasonable suspicion. The officer must still have specific facts warranting a stop, but not necessarily know whether a crime has been or will be committed. This is the pretext often used by police for “stop and frisk” encounters, and the fact that Gray was in an identifiable high-crime neighborhood adds to the justification by police.

“Courts have found that flight from police presence in a high-crime area creates reasonable suspicion warranting an investigatory stop,” said Michael Grieco, a former Miami-Dade County prosecutor now in private practice. “Police are only supposed to use enough reasonable force for apprehension and we are repeatedly seeing the products of excessive tactics.”

Others said courts have split on exactly what reasonable suspicion entails. Donald M. Jones, a University of Miami law professor and Baltimore native, said Gray’s act of simply running away may not have been enough.

“That is very thin. People run for many reasons. Many people have reasons to be afraid of the police,” Jones said. “I think that is ambiguous, but the courts are divided on that.”

In some cases, video recordings might add clarity: In North Charleston, South Carolina, police officer Michael Slager was charged with murder after a bystander recorded him shooting of Walter Scott, who was unarmed and running away from Slager’s Taser following an April 4 traffic stop.

The Supreme Court has ruled that officers can use deadly force against an escaping suspect only if they believe the person poses “a significant threat of death or serious physical injury” to the officers or someone else. Use of less-than-lethal force also requires officers to determine the seriousness of the suspected crime, and whether the suspect poses a safety threat or is attempting to evade arrest.

Legal experts say that when acting under reasonable suspicion, police generally are not supposed to use force to apprehend someone or slap handcuffs on them — unless their subsequent conversation or frisk turns up evidence of a crime or a weapon, such as a gun. In Baltimore, Gray had the knife, but it’s not clear that simply possessing it was enough to arrest him.

“The nature of the evidence is important,” Moreno said. “The knife cannot possibly substantiate any concern the police might have had with public safety, because they couldn’t see it. It’s a difficult thing. You have to look at it step by step by step.”

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