Byrne’s federal case has also been complicated by a number of motions to exclude evidence from the trial, coming from both sides of the aisle.

Late last month, Judge Richard G. Stearns allowed a defense motion to exclude references to two previous incidents involving Byrne.

One occurred in September 1991, when Byrne allegedly assaulted Joseph Mulry, a patron of the Jukebox, a nightclub where Byrne worked part-time. Stearns prohibited the prosecution from entering evidence of the Mulry case for the time being, but mentioned in his ruling that the prosecutors might attempt to bring it up later.

The second concerned an alleged screaming outburst directed by Byrne at a man, Michael Tiberio, walking down Tremont Street in June 1998. Stearns ruled that this incident was irrelevant to the case involving Trombly because it “establishes no more than that the defendant has a bad temper, which he has displayed in the past.” Stearns said this constituted an impermissible attempt to use past evidence of bad character in order to prove later accusations.

In January 2002, the head of the BPD union had claimed that Byrne’s prosecution had been taken over by federal authorities because Trombly was “a white, affluent Harvard student.” In July, the U.S. Attorney’s office filed a motion to exclude evidence that Trombly had worked at a Cape Cod country club frequented by Boston Police Commissioner Paul F. Evans. Stearns denied this motion.

Also in late July of this year, Byrne’s attorney filed a failed motion to allow an extended questionnaire to be filled out by potential jurors—covering issues such as police brutality—in addition to the standard juror-selection queries. Stearns simultaneously denied a defense motion to give jurors a guided in-person tour of the Brighton, Mass. district station house in which Trombly was allegedly beaten.

Through all these legal twists, Davis said he has had almost no contact with the prosecution, for whom he is to testify.

“I haven’t really been prepped at all,” he said. “I guess they’re waiting for confirmation that the next trial date is actually going to happen.”

And after so much time, Davis said he is eager to get his involvement in Byrne’s prosecution over with.

“Garett, myself and I know a lot of other witnesses have graduated from college and have gone their own ways,” he said. “It’s just interfering with people’s lives...With all these postponements, I’m beginning to lose faith in the judicial system, at least in the city of Boston.”

Davis said he had remained close with Trombly since the incident, though they had been forced to curtail the scenes of their socializing.

“Ever since that incident, [Trombly] never came to BC anymore for obvious reasons,” Davis said, adding that he himself “was never much of a Cambridge fan.”

In an unrelated case, Byrne and a number of other white police officers have filed a civil suit against the BPD, charging reverse discrimination in job promotions as a result of the affirmative action policy established by the BPD in response to a suit in the 1980s. That suit is scheduled to go to trial in October.

Byrne could not be reached for comment.

—David H. Gellis contributed to the reporting of this story.

—Staff writer Simon W. Vozick-Levinson can be reached at vozick@fas.harvard.edu.