Fitzpatrick, the first defense witness called after more than six weeks of prosecution witness testimony, said he was especially worried about the FBI's relationship with Bulger in the case of Edward "Brian" Halloran, a man who had provided the FBI with information about Bulger's alleged involvement in a 1981 killing.
Fitzpatrick said he met with a federal prosecutor in an attempt to get Halloran into the witness protection program. Halloran was gunned down two days later along with a man driving him home— killings prosecutors have accused Bulger of committing.
During cross-examination, Assistant U.S. Attorney Brian Kelly repeatedly asked Fitzpatrick if he is "a man who likes to make up stories" and suggested he falsely claimed credit for having a key role in several high-profile cases, some contained in his book on Bulger, "Betrayal."
Kelly asked Fitzpatrick about claims he found the gun used to kill Martin Luther King Jr. in 1968 and passages from his book in which he says he arrested Boston Mafia underboss Gennaro Angiulo in 1983.
Kelly read from FBI reports that Memphis police had found the gun and other agents made the Angiulo arrest.
Fitzpatrick stood his ground, saying he'd been with the officers who found the rifle and was the supervisor of the agents who arrested Angiulo.
Kelly also suggested that Fitzpatrick implied in his book that he helped find the body of John McIntyre, a Quincy fisherman allegedly killed by Bulger.
Kelly said one photo in the book shows McIntyre standing in a field wearing a trenchcoat, on the other side of the page is a photo of investigators removing McIntyre's body from a burial site in Boston in 2000.
Fitzpatrick acknowledged that he was not present when McIntyre's body was unearthed.
Fitzpatrick will be back on the witness stand Tuesday.