Bulger's defense lawyers had sought to limit testimony from relatives of the 19 people he and his cohorts are accused of killing.
Attorney J.W. Carney Jr. argued during a pretrial hearing Monday that the families shouldn't be allowed to give victim impact statements like those given during sentencing hearings.
Assistant U.S. Attorney Brian Kelly said they would focus only on factual information, including asking the relatives to identify their loved ones in photos taken after they were killed.
"We do not intend to turn it into a sentencing hearing," Kelly said.
The issue was among more than a dozen pretrial motions heard by U.S. District Court Judge Denise Casper on the eve of Bulger's trial. Jury selection is to begin Tuesday.
Bulger, 83, is charged with a long list of crimes, including participating in 19 killings, in a broad racketeering indictment. Authorities say he committed the crimes while he was an FBI informant.
Bulger fled Boston in 1994 and remained one of the nation's most wanted fugitives until he was captured with his girlfriend in Santa Monica, Calif., in 2011.
The judge ruled that Bulger's FBI informant file can be admitted as evidence during the trial. Prosecutors have said the file contains more than 700 pages of documents chronicling Bulger's role as an informant who provided information on the New England Mafia, his group's main rival.
Bulger's lawyers deny that he was an informant but had planned to use his claim that he received immunity from a federal prosecutor as a defense at trial.
The judge rejected that request in an earlier ruling, finding that any purported immunity agreement was "not a defense to the crimes charged."
Kelly, the prosecutor, argued Monday that Bulger's lawyers appeared to be trying to use the immunity defense despite the judge's ruling. He cited the defense witness list, which includes FBI Director Robert Mueller, former Gov. William Weld and U.S. District Judge Richard Stearns, all of whom worked in the U.S. attorney's office in Boston when Bulger claims he received immunity from another federal prosecutor in the office.
"It seems clear to us that they are trying to put that evidence before the jury in some fashion," Kelly said.
Carney, Bulger's attorney, said the defense has "other reasons" for calling the men as witnesses, but he did not elaborate.
The government's witness list includes a collection of notorious gangsters, including Bulger's former partner, Stephen "The Rifleman" Flemmi, who's serving a life sentence after pleading guilty in 10 murders. Former hitman John Martorano, who admitted killing 20 people, also is expected to testify.
Beginning Tuesday, a pool of 675 people will be called for jury duty. Potential jurors will spend Tuesday and Wednesday filling out questionnaires to be used to screen out people with conflicts. Once the pool is winnowed down, potential jurors will be questioned individually.
The judge has said she hopes to complete the selection process Friday, with opening statements from prosecutors and defense attorneys expected June 10.
Twelve jurors and six alternates will be chosen to sit for the trial, expected to last three months. The judge said the jurors' names won't be made public until after they deliver their verdict.