Boston (CNN) -- Courtroom drama erupted Friday when James "Whitey" Bulger stood and angrily addressed the judge, without the jury present, about how his murder trial was "a sham" and he wasn't going to take the stand in his own defense.
That provoked an outburst from the widow of a man who is among 19 people Bulger is charged with killing. The judge quickly restored order.
Bulger told the court Friday why he won't testify.
"My thing is...I didn't get a fair trial. This is a sham. Do what ya's want with me," the reputed Irish mafia boss told the federal judge.
His voice shaking, the 83-year-old Bulger told the judge he had a deal with now-deceased Jeremiah O'Sullivan, the head of the Justice Department's New England Organized Crime Strike Force who later became U.S. attorney in Boston during the height of Bulger's allegedly brutal reign.
"In return he promised to give me immunity. As far as I'm concerned I didn't get a fair trial," Bulger said.
He didn't elaborate on what the agreement was.
Judge Denise Casper questioned Bulger on his decision not to testify.
Bulger responded: "I'm making the choice involuntarily. I feel I've been choked off from making an adequate defense."
At one point, the widow of a man whom Bulger allegedly killed interrupted proceedings with an outburst.
"You're a coward!" Patricia Donahue asserted when Bulger indicated he would not testify.
Casper called for "silence" in the gallery. Bulger is charged with killing Donahue's husband, Michael.
Jurors were not present when Bulger spoke or when Donahue made her outburst. When the jury returned to the courtroom, the defense rested, concluding 35 days of testimony.
Bulger's claim to immunity seemed to contradict his legal defense: His lawyers spent a large part of the seven-week trial disputing assertions that Bulger was an FBI informant.
The judge previously ruled that Bulger could not argue immunity as defense in this trial.
The jury will begin hearing closing arguments Monday.
Outside of court, Tommy Donahue, son of Michael Donahue, shared his mother's sentiment and called Bulger "a rat coward."
"He is going to take his secrets to the grave with him," Donahue said of Bulger.
Before resting its case, the defense read aloud the prior deposition of one witness who has brain cancer and could not deliver testimony in person.
In all, the defense called 10 witnesses over five days.
Prosecutors called 63 witnesses.
One of the witnesses did double duty, called to the stand by each side.
That means the jury heard from a total of 72 witnesses over the 35 days.
Bulger's defense team said earlier in the day that Bulger is prepared to forfeit the assets found in his Santa Monica, California, apartment to the families of two men he is accused of murdering.
Nearly $822,000 was found in the alleged Boston Irish mob boss's possession when he was arrested in 2011.
"My client is prepared to have all the money forfeited to the victims' family that prevailed at trial first, but had it reversed because of ... a highly technical (court) process," J.W. Carney said Friday.
The families of alleged murder victims Donahue and Brian Halloran -- whom Bulger is also accused of killing -- won a judgment in 2009, but an appeals court tossed it out, saying the suit was filed too late.
The Donahue family has been in court virtually every day of this trial.
There remains a question as to whether Bulger's offer is a meaningful one. The government has seized the money, so technically it no longer belongs to Bulger. Only if he is found innocent and the money is found to have been earned legitimately would it be returned.
Carney confirmed outside of court that Bulger's decision not to testify was made shortly before it was announced, after his client heard all of the witness testimony.
Tommy Donahue expressed appreciation to Bulger's defense attorneys Hank Brennan and Carney.
"I tip my hat to Carney and Brennan," Tommy Donahue said, referring to the gesture of forfeiting Bulger's recovered assets to his family and Halloran's family.
In a 32-count indictment, prosecutors accuse Bulger of participating in 19 murders, racketeering, money laundering and extortion during some two decades.
CNN's Kristina Sgueglia and Deborah Feyerick contributed from Boston and Michael Martinez wrote from Los Angeles. Ross Levitt contributed to the report.