Najee Rivera admits he panicked on the night two white Philadelphia cops pulled over his motor scooter in El Centro de Oro, a Latino ghetto in the city’s Fairhill section.

“To be honest, I was afraid,” Rivera said. “I saw them get out of their car with nightsticks. I heard one of them call me a spic. I hadn’t done anything wrong, so I took off. I shouldn’t have, but I was scared of them.”

With good reason. A private security camera captured what happened next:

As Rivera puttered along at perhaps 25mph, the police car raced up alongside him. The cop on the passenger side leaned out the window and clocked Rivera on the back on the head with his truncheon, knocking him off his scooter to the pavement. Officers Kevin Robinson and Sean McKnight bounded from the car and began clubbing Rivera as he lay wailing. They hauled him to his feet, slammed him against a building and then drove him back into the sidewalk.

When the beating was over that night, May 29, 2013, Rivera’s wounds required 38 surgical staples to his head and 18 stitches to his face. His nose was broken, an ear was gashed and the orbital socket of his right eye, swollen and plum-colored, was fractured.

The felonious assault on Rivera, then 21, was covered up by Robinson and McKnight with the familiar police-report narrative: The perp was resisting and the cops felt endangered, so they used “necessary force.” The truth came to light in February, when Rivera’s girlfriend, a South Philly nurse named Dina Scannapieco, revealed the smoking-gun security video. The cops were suspended and charged with aggravated assault.

Rivera’s story represents a broader trend in police violence that has been largely overlooked in the recent headline examples, from Cleveland to South Carolina, Baltimore to San Bernardino, Calif. Many of the most appalling examples of police brutality seem to spring from an officer’s rage when a citizen has the audacity to flee. Too many police officers can’t resist a pursuit—on foot or in a patrol car—even though they’ve been schooled repeatedly on the narrow parameters for permissible chases.

Pissing Off Police

“It’s called contempt of cop or POP: pissing off police,” says Geoffrey Alpert, a University of South Carolina criminologist and leading expert on police violence and pursuits. “These guys have a sworn duty to catch the bad guys, and that becomes an overwhelming instinct when someone runs from them. They’re going to try to catch them.”

And when they do, bad things often happen. Nothing seems to transform an otherwise reasonable police officer into a crazed beast faster than someone who flees.

“The psychology of pursuits is a very important factor in so many of these brutality cases, but no one seems to want to pay much attention to it,” says Gregory Gilbertson, a former Atlanta cop who teaches criminal justice at colleges in the Seattle area.

It’s impossible to know how many examples of police violence begin with pursuit rage since the U.S. declines to compile statistics on shootings and assaults by cops. As a result, no one can thoughtfully analyze the genesis of these events, much less make recommendations for how they can be minimized. But a growing record of anecdotal examples—many substantiated by police dash-cams or video shot by witnesses—suggests a pattern.

In one of the more bizarre recent examples, two deputies delivered blows and boots to the head and groin of Frank Pusok, 30, who led law enforcers on a long pursuit by car and on horseback in the Mojave Desert of San Bernardino County, Calif. after Pusok stole a horse. The April 9 beating was captured on video by a news helicopter. Pusok had surrendered and was spread-eagled on his belly when the beating commenced. Each of 10 deputies could not resist getting in a lick or two as they arrived, long after the suspect was handcuffed. They’ve been suspended and may face criminal charges. The county paid Pusok a preemptory settlement of $650,000.

That assault was five days after the shocking shooting death of Walter Scott, 50, who lumbered away from Officer Michael Slager following a run-of-the-mill traffic stop in North Charleston, S.C. Slager fired eight shots, five of which hit Scott in the back. A brief recorded conversation between Slager and a police supervisor after the shooting hints at a crucial component of police pursuits.

“By the time you get home,” the supervisor said, “it would probably be a good idea to kind of jot down your thoughts on what happened. You know, once the adrenaline quits pumping.”

“It’s pumping,” Slager said, laughing nervously.

All About Adrenaline

I asked Sam Walker, an emeritus professor of criminology at the University of Nebraska Omaha and expert on police misconduct, why cops turn psycho during pursuits.

He replied, “Adrenaline, adrenaline and adrenaline, compounded by a failure of the department to adequately train its officers to think about the department’s policies that are designed to curb instincts and impulses and to act rationally and carefully.”

“Police officers engage in these chases then say, It was just my adrenaline,” adds Seattle’s Gilbertson. “Please. You are trained to contain your emotions. That is part of your job—to make rational decisions and judgments while under stress.”

“I think most cops view running from them as a crime, even though intellectually they must know it’s not because they have been told in training, or should have been told,” Gilbertson says. “When someone runs, too many officers seem to really believe that they have a right to chase them down and use whatever force is necessary to subdue them.”

In fact, case law and widely accepted police protocols (based on research by South Carolina’s Alpert dating to the 1980s) strictly limit permissible pursuits, both on foot and in vehicles, to those involving suspects in violent felonies or those who may present imminent risk to the public or police.

This is from a primer on auto pursuits by the International Association of Chiefs of Police:

High speed pursuit driving creates enormous civil liability exposures for police officers and agencies and can result in criminal prosecution of police officers as well. Few areas of police work involve higher stakes. The need to conduct some high speed pursuits is obvious to most. Equally obvious is the need to protect the public (and police officers themselves) from unnecessary risks created by indiscriminate high speed chases.

Gilbertson says most pursuits are “totally unwarranted” and “indicate a lack of good order, discipline and supervision in the field.”

“We’ve known about car-pursuit dangers for decades now, and foot pursuits may be even more dangerous,” he says. “And yet most police pursuits still start with minor infractions or an officer’s suspicions. It’s crazy.”

“None of these cases ever begins with an officer saying, I’m going to go out and kill somebody,” Alpert told me. “But the process is the same. You get ramped up, you get excited, and you get yourself deeply invested emotionally in a pursuit. You think what you’re doing is right, you believe what you’re doing is right, but it turns out not to be right.”

‘Grumpy and Frustrated’

Cops involved in a chase can feel a sense of “righteous indignation,” says Rodger Broome, who spent 17 years in law enforcement in Utah and now teaches at Utah Valley State University in Orem and volunteers as a reserve officer.

“You might be thinking, This person is going to kill me and take me away from family,” Broome says. “So, yes, some of us do tend to take it personally, like, You’re not going to make an orphan out of my kid.”

Certain officers can’t resist acting out with physical retribution.

“Sure, you’re probably a little grumpy and frustrated with the guy when you catch up to him,” says Gilbertson. “An officer will personalize or internalize the fact that they were running from me. Well, it’s not personal. They are running from the law, running from a uniform, for whatever reasons they might have. We might not think it’s a legitimate reason, but that’s not necessarily our business. They have their reasons. That’s their prerogative.”

Whether it was adrenaline, righteous indignation or group-think, police in Cleveland personalized a chase on Nov. 29, 2012. It begin with an unconfirmed report that someone had fired a shot near police headquarters in the city.

Officers “believed” the shot had come from a car driven by Timothy Russell, 43, according to the Cleveland Plain Dealer. A long, perilous police pursuit began, reaching speeds of 110mph. By the time the chase ended 25 minutes later, 62 police cars and 104 of the 277 Cleveland cops on duty that night had joined in.

When Russell finally stopped, 13 officers fired a fusillade of 137 bullets into his car. One officer, Michael Brelo, climbed atop the car’s hood and fired 49 shots. Russell was hit 23 times and his passenger, Malissa Williams, 24 times. Both were killed. No weapon was found in the car, and no evidence linked Russell to the report of the shot.

Brelo, 31, a five-year police veteran and an ex-Marine who had served in Iraq, went on trial for manslaughter this month. He was awaiting a verdict this week. His union president has called him a hero. Meanwhile, Cleveland has agreed to pay the victims’ families $3 million.

The rest of this article is available on alternet.org

This story written by David J. Krajicek for AlterNet