The gang member, Robert Simon, 45, who was also known as Mudman, showed no emotion as the verdict was pronounced. The jury of five men and seven women had deliberated 11 hours over two days before returning the verdict.

Mr. Simon pleaded guilty last October to capital murder in the shooting death of Sgt. Ippolito Gonzalez of the Franklin Township police in May 1995. Mr. Simon tried to retract his guilty plea in February by saying he had been coerced, but the judge rejected that contention.

In the penalty phase of the trial, defense lawyers had maintained that Mr. Simon should be spared a death sentence, contending in part that he had been abused as a child. But the prosecution asserted that Sergeant Gonzalez had been killed in the line of duty and that Mr. Simon had previously committed another murder.

The judge, Joseph Lisa of Superior Court, set an execution date of May 21. But the sentence is subject to review by the State Supreme Court and may take years to resolve.

Sergeant Gonzalez, 40, of Buena, N.J., was killed moments after pulling over Mr. Simon and Charles Staples, Mr. Simon's co-defendant and also a member of the Warlock motorcycle gang. Mr. Staples was convicted of felony murder and sentenced to life in prison.

The gang members had broken into a business just before Sergeant Gonzalez stopped them. Mr. Simon has said he shot Sergeant Gonzalez because he did not want to return to prison. The shooting occurred near the Franklin Township police station. Officers heard the shots, rushed to the scene and arrested Mr. Simon and Mr. Staples after a brief chase.

Mr. Simon had been paroled 11 weeks before the murder after spending about 12 1/2 years in a Pennsylvania prison for killing his 19-year-old girlfriend in 1974.

By Iver Peterson - The New York Times

June 23, 2001

In a trial drenched in the brutal realities of prison life, a convicted killer was acquitted yesterday of stomping a fellow condemned prisoner to death.

During the three-week trial, Robert F. Gold, the lawyer for the acknowledged jailhouse killer, Ambrose Harris, persuaded the 12 members of the jury that Mr. Harris, 49, had reason to believe he was being set up by guards to be attacked by Robert Simon, a three-time murderer. The two were already enemies when they were placed together, against regulations, in a recreation cage at New Jersey State Prison in September 1999.

During the trial in State Superior Court in Freehold, prosecutors were not able to undermine witness testimony that Mr. Simon, who bragged of having murdered an inmate in a Pennsylvania jail, attacked first. And there was also no dispute that Mr. Harris, who is sentenced to die for killing a young woman he kidnapped, punched and kicked Mr. Simon to death. The attack ended with Mr. Harris's jumping off a table onto Mr. Simon's shattered head.

It was the first case of a death-row killing in the state's modern history, the Mercer County prosecutor, Daniel G. Giaquinto, said during the trial.

To support his contention that Mr. Harris, a huge, bullet-headed man, would be afraid of the slightly smaller Mr. Simon, Mr. Gold stressed that Mr. Harris had been in administrative segregation from other prisoners for hitting a guard, and should not have been placed in a recreation cage with other prisoners while the death-row cells were fumigated.

Mr. Gold also called witnesses to testify that Mr. Simon, once a member of a white-supremacist motorcycle gang, had repeatedly taunted Mr. Harris, who is black. And the defense went on to persuade the jury that Mr. Harris believed he had been handed over to Mr. Simon by the guards.

''You had to look at this from Harris's point of view, and his honest and reasonable belief that he was getting set up'' Mr. Gold said after the trial.

Mr. Giaquinto, the prosecutor, tried to remind the jury of the brutality of Mr. Harris's attack, and of the fact that he kept stamping and jumping on Mr. Simon's head long after Mr. Simon had ceased to move or to pose a threat. Mr. Harris also ignored the guards, who were not allowed to enter the cage with the prisoners without permission, screaming for him to stop.

Mr. Giaquinto maintained that Mr. Harris persisted to make a reputation for himself among the inmates.

Mr. Gold attacked the prosecution's argument that the attack had lasted too long to be considered self-defense by presenting testimony by Craig Haney, a professor of psychology at the University of California at Santa Cruz and an expert on prison life. Mr. Haney introduced the term ''prisonization'' to describe a mindset among convicts that they must defend themselves to the death or face becoming a victim.

''Prison -- I don't care what prison -- they're dangerous places,'' Mr. Gold said in an interview after the verdict. ''These guys learn that they have to watch their backs, their fronts, their sides and at the slightest sign of weakness, or they're a victim.''