It was “the worst case of police brutality” in Boston history—and the victim was himself a Boston cop.

Author Dick Lehr told the story of Officer Michael Cox during a forum last night at the Harvard Kennedy School to illustrate a “code of silence” that he and other speakers said is an “informal culture” among police officers around the world.

One night in 1995, Cox was mistaken for a gang member and severely beaten by fellow officers, recounted Lehr, also a Boston University journalism professor.

Afterward, several police officers lied in reports and Cox’s severe injuries were explained as a “slip on the ice,” so that the police officers who beat him received minimal punishment, said Lehr, who wrote about the case in his book, “The Fence: A Police Cover-up Along Boston’s Racial Divide.”

By refusing to reveal the wrongdoing of their fellow officers, police endanger the credibility and honesty of their departments, concluded members of the panel.

Malcolm Sparrow, a Kennedy School professor, drew both from academia and his experiences as a former detective chief inspector of the British Police Service, saying he was asked to lie in a police report just three months after joining the force. “You get the impression that their integrity is at zero,” he said of many police agencies.

Ronald Davis, the chief of police in East Palo Alto, Calif., and former captain of the Oakland Police Department, said the “code of silence is not a sinister plot—that’s what makes it so dangerous.” He said officers fear that telling the truth about colleagues’ misdeeds will harm their careers, and he tries to encourage openness. “Police solidarity,” he said, comes from a “we versus them mentality”, which he agreed leads to a “distorted view of justice.”

The seats of Bell Hall were packed and some of the roughly 70 people who attended stood along the walls or sat on the floor. The audience included students, but also Cambridge residents, a member of the American Civil Liberties Union of Massachusetts, and a Boston police officer, in uniform.