Michael Avery, a Boston defense attorney, is co-author of a standard text, "Police Misconduct: Law and Litigation." Recently, in an indignant speech at the annual dinner of the Civil Liberties Union of Massachusetts, Avery charged there is a conspiracy to protect police officers who commit perjury. Avery focused on Massachusetts, but he believes that "the code of silence" concerning false testimony by the police is in operation throughout the country.

"Every judge," Avery said, "who sits in the criminal courts of the Commonwealth of Massachusetts routinely has appearing before him or her police officers who commit perjury in order to make charges stick in criminal cases. Everyone knows this, yet few judges would admit it, and none have addressed the problemwith any intention of doing anything meaningful about it."

I asked a prominent, usually very cautious, judge in New York about Michael Avery's accusation. "Oh sure," he said, without hesitation, "cops often lie on the stand. But we don't have enough proof to do anything about it."

Michael Avery concedes that judges are not the main culprits in this matter. "The principal villains in the conspiracy of silence," says Avery, "are those lawyers in the offices of district attorneys and the attorney general who do nothing about police perjury."

Why, then, I asked Avery, don't more defense attorneys blow the whistle? "Because," he said, "a defense attorney needs favors to make this system work." He or she has to be on reasonably good terms with judges and assistant DAs with regard to court calendars, plea bargaining and other parts of the system. Avery, however, prefers to speak out anyway; and because of his formidable courtroom skills, he does not lack for clients.

Reacting to Avery's Boston speech, another attorney told me of his experience with police perjury. Burton Weinstein, who practices in Connecticut, is an American Rumpole in that he is dogged, canny and, when necessary, daring. He was defending a woman charged by the police with starting a riot in a dance hall by shutting off the lights. A policeman testified unequivocally that he had been on the dance floor at the time and had been able to see her switch off the lights.

The judge granted a motion by Weinstein that the prosecutor, the judge, the court stenographer and the defense attorney go to the dance hall to check out the cop's account. It turned out that the only place from which the lights could be turned off was behind a brick wall. Standing on the dance floor, the policeman could not have seen the defendant, or anybody else, switch off the lights.

Back in court, Weinstein asked permission, which was granted, to give the policeman his Miranda warnings. He hen reminded the cop that he was testifying under oath, and that the penalty for perjury was a five-year jail term. Did the cop still stand by his testimoney? The policeman said he most certainly did. Weinstein made a motion that the cop be suspended and the transcript of his testimony turned over to the state's attorney for perjury prosecution. The judge declined to accept that motion.

Weinstein then turned to the prosecutor, reminded him that he too was an officer of the court and that he knew the cop had been lying because the prosecutor had also seen the brick wall. The prosecutor looked away from Weinstein. Weinstein eventually won his case, but not even a reprimand was placed in the file of the policeman.

Richard Emery, who does much of the police misconduct work for the New York Civil Liberties Union, suggests that there be a special prosecutor in every jurisdiction who would investigate all charges of police abuse -- including perjury. The regular prosecutors, Emery notes, "have to rely on the local cops to make their cases, so they are not eager to go after them."

"I've been a lawyer for a long time," says Emery, "but I am still shocked that the first line of law enforcement in our society can get away with routinely lying in court. And once a cop has broken the law, he can no longer look at himself the same way he did when he came onto the force."