It went viral on YouTube and aired on a nearly continuous loop for a week on cable news networks, but the March 3 confrontation between a University of Maryland student and the Prince George's County police force dramatizes an even bigger change: the revolution in law enforcement wrought by video recorders and cell-phone cameras.
It began with the 1991 videotaped beating of Rodney King that sparked citywide riots in Los Angeles, but the modern ubiquity of video recording devices — and the likelihood that bystanders and even the suspects may be taping an incident — has had a major effect on the theory and practice of law enforcement.
"There's not a police academy in the country that doesn't use the Rodney King video," said Wolcott, Conn., police Chief Neil O'Leary. "I will tell you that officer actions 30 years ago are very different than officer actions today."
In cases of suspected police brutality or misconduct, lawyer Christopher Griffiths said, "For years, you were dependent on the client's version [of events]. We're seeing with video that cameras don't lie."
Mr. Griffiths is representing John McKenna, the University of Maryland student caught on the gripping video shot by a bystander as he joined a raucous street celebration to mark Maryland's upset win over rival Duke University in basketball.
As the student walked near two police officers on horseback, three Prince George's County police officers in riot gear attacked and beat him with batons. It was not evident from the video what, if anything, Mr. McKenna might have done to provoke the confrontation.
Mr. McKenna suffered a concussion and a head wound that required stitches, and faced charges — later dropped — that he had assaulted two officers on horseback and received his injuries from the horses.
He plans to sue the county for the attack, and the video will be a cornerstone of his case. Mr. Griffiths said the existence of independent video in so many recent law enforcement cases has helped level the playing field in the courtroom over such charges.
"When this case plays itself out, I'm hopeful there will finally be changes in the police department," the lawyer said. "We hope there will be a criminal prosecution."
As in so many other recent cases, more video evidence of the incident may be forthcoming. After some delay, nearly 90 minutes of footage shot by a University of Maryland security camera was given to attorneys for Mr. McKenna. The footage had been missing from nearly 60 hours of school video originally turned over after Mr. Kenna's attorneys obtained a subpoena in the days after the attack.
In a second recent incident, a police task force in Harrisonburg, Va., said Wednesday that it will be reviewing official video and videos posted on the Internet as part of its review of a violence-marred student block party April 10 that resulted in 30 arrests. Police used pepper spray and tear gas to disperse revelers, some of whom threw bottles and rocks at officers.
A search of YouTube for the term "police brutality" produces more than 14,000 entries.
The Department of Justice investigates cases of purported police brutality, and spokesman Alejandro Miyar said the department considers all evidence available, including video, in all investigations.
"The FBI is investigating the incident that occurred after a University of Maryland basketball game. The Civil Rights Division will review the FBI's findings to determine if there was a violation of federal civil rights laws," he said in an e-mail.
Mark Newbold, lead attorney for the Charlotte-Mecklenburg Police Department in North Carolina, said that while having video evidence of police actions can be useful in post-incident investigations, videos do not always provide the complete context of an event.
"You still have to look at what the officer perceives," he said.
Mr. Newbold said in police brutality cases in which video evidence is involved, it is important for a jury to understand that videos display only one perspective of an event and that different angles and lighting could better explain or justify the actions taken by officers on the scene.
He cited an example in which one video made it appear that officers had shot a man in the back, when a video taken from another angle showed that the man had turned slightly toward the officers with a weapon.
Difficult split-second decisions "have to be taken from the framework of what the officer is confronted with," Mr. Newbold said.
Chief O'Leary, of the Wolcott, Conn., police and many other law enforcement professionals say the explosion of video recordings of public events can work to the benefit of police officers. Many times independent video helps to exonerate the police, showing their reactions were reasonable.
When he was chief of police in nearby Waterbury, Conn., Chief O'Leary recalled, two off-duty officers were involved in a disturbance outside of a bar, in which they were later accused of beating civilians. The cameras from a state building's security camera across the street recorded the event, but in this case the video exonerated the officers as it showed that they had not used excessive force.
Chief O'Leary said the increased presence of video is better for both the police and the public. Officers are held to a higher level of conduct in treatment of civilians and are compelled to be more conscious of their behavior, but they also can be protected against unfair charges of brutality or overreaction.
Although Chief O'Leary agreed that police behavior sometimes can appear brutal to civilians even though officers might be using standard and appropriate procedures, he did not condone the actions of the Prince George's County officers based on the video evidence he saw.
"That student was brutalized," he said. "There's no justification for that at all."