Vulgarities Fly Between Key Witness and Bulger BOSTON - Kevin Weeks, once a surrogate son of the notorious South Boston crime boss James (Whitey) Bulger, issued a threat from the witness stand to Mr. Bulger's lawyer in Federal District Court here on Tuesday. Then the proceedings turned ugly. Mr. Weeks, a key government witness, had testified that he watched Mr. Bulger kill four men and one woman. Sometimes, he said, Mr. Bulger would then go lie down, leaving others to clean up the bloody mess. So when it was time for cross-examination, Mr. Bulger's lawyer, J. W. Carney Jr., painted Mr. Weeks as a lying, selfish thug who had wheedled a sweetheart plea deal of five years in prison for aiding and abetting the murders of five people, all in return for providing evidence against Mr. Bulger and others. Temper rising, Mr. Weeks shot back: "What did I win? Five people are dead. "We killed people that were rats," he added, "and I had the two biggest rats right next to me!" This was a reference to Mr. Bulger and another gangster, Stephen Flemmi. Mr. Bulger does not like being called a rat, a k a an informer. And so the frail-looking 83-year-old defendant in bluejeans, white sneakers and a dark blue shirt spat a vulgarity, his first words in more than 16 years to Mr. Weeks, whom he had long treated as a son and groomed as a successor. Mr. Weeks, still on the stand, shouted a two-word expletive of his own, and Mr. Bulger replied in kind. "Hey!" the judge interjected. Earlier, Mr. Weeks had described how tough it was to testify against Mr. Bulger, likening him to an older brother. But now, glaring at his former mentor, he added, "What do you want to do!" With Mr. Weeks unhinged, Mr. Carney soon rested his cross-examination. It was the most dramatic day in the trial of Mr. Bulger, who was arrested in California in 2011 after 16 years on the run. He has pleaded not guilty to a long list of federal charges, including allegations that he played a role in 19 murders. Trying to show jurors that Mr. Weeks was not to be believed, Mr. Carney had tripped up the witness about who might have been the second gunman in a 1982 assassination. He also prodded Mr. Weeks to admit that anyone who called him a rat would have "a problem," meaning they would be hurt. Mr. Carney then asked, What if I called you a rat? Call me that outside and see what happens, Mr. Weeks responded. Mr. Carney also elicited this statement from Mr. Weeks: "I've been lying my whole life. I'm a criminal. In macabre testimony earlier in the day, the witness tied Mr. Bulger directly to three killings, with details that combined the mundane and the horrific. He described how Mr. Bulger used a MAC-10 machine pistol to shoot one extortion victim in the head, then "went upstairs and lay down on the couch while we took care of the cleanup." For that Mr. Flemmi, who was known as the Rifleman, offered tips, Mr. Weeks said: "He explained to me that cold water helps congeal the blood and everything." Another time, Mr. Weeks said, he watched Mr. Bulger and Mr. Flemmi garrote and strangle Mr. Flemmi's stepdaughter. Then Mr. Bulger gave Mr. Flemmi a new handle, inspired by his partner's enthusiasm. "Jim gave him the nickname "Dr. Mengele," because he kind of enjoyed it," Mr. Weeks testified. Sometimes, there were problems finding rope. After the gangsters tried to smuggle weapons to the Irish Republican Army on a boat in 1984, Mr. Bulger's F.B.I. handler, John Connolly, told him that one of the crew members had informed the authorities about the failed effort, Mr. Weeks said. Mr. Bulger confronted the crew member, John McIntyre, who confessed to revealing the scheme, Mr. Weeks said. Mr. Bulger then slipped a rope around Mr. McIntyre's neck and tried to strangle him, Mr. Weeks said, but the rope was too thick. Mr. McIntyre gagged and started vomiting, so Mr. Bulger shot him in the head and shot him in the face as he lay on the ground, the witness testified. A federal judge found the government liable for Mr. McIntyre's death because Mr. Connolly had leaked enough information to identify Mr. McIntyre as an informer. The three victims whose gruesome demise Mr. Weeks described on Tuesday were buried in the basement of a South Boston home. But the corpses had to be moved when the house was sold. Mr. Weeks said he eventually led investigators to where the bodies had been reburied. Why not just buy the house and leave them there? "We figured it would be easier to move the bodies," Mr. Weeks said. Cheaper, too.