James "Whitey" Bulger, whose racketeering trial continues to be the best show in town, finally flashed a smile from his seat at the defense table Friday, although it was unclear from the context whether Bulger found one of his accusers amusing or was simply recalling better times.

The witness was Richard "Dickie" O'Brien, an understated, south shore bookmaker, now 84 and retired to Florida. With his blue blazer, buttoned-down collar and striped tie, O'Brien looked as if he might have arrived in federal court from the yacht club.

The government called him to testify about events in the early 1970s, which was when news reached Bulger's Winter Hill Gang that O'Brien was running his Quincy office independently, meaning that he had been freed by a series of arrests from paying protection, or rent, to Boston's Italian mob, sometimes referred to as The North End.

"Mr. Bulger wanted to talk to me," O'Brien said. "He said, in so many words, 'You are by yourself now.' And he said, 'I think you should be with us.' I said, 'Well, I was with The North End.' He said, 'Forget The North End. If you want to be in business, you are with us.' That was put down as law."

O'Brien said he knew he was not being presented with a choice. He began paying Bulger's gang what would become $2,000 — and in many cases substantially more — every month, until O'Brien himself was arrested in the late 1990s.

"Of course, I had heard about them because their reputation had always preceded them, that they were very capable," O'Brien said.

"What do you mean by capable?" Assistant U.S. Attorney Zachery Hafer asked.

"They had a gang war in South Boston and people were shot," O'Brien said, "And Mr. Bulger ended up on top. You can draw your own conclusions."

"Why did you agree to pay rent?" O'Brien was asked.

"I valued my own life," he said, "as well as those with me."

O'Brien was no newcomer to the gambling racket. He inherited the business from his father and passed it on to a daughter when he retired. Once, when summoned to a meeting with a Bulger associate, O'Brien said he ordered his daughter to call the FBI's Miami office if he was not back in 12 hours. He said he had became suspicious of agents in the Boston office after learning that Bulger was providing sliding glass doors for a home owned by a Boston agent.

But despite O'Brien's apparent distaste for Bulger's violence, he benefited, more than once.

He said he once dragged a business associate who owed him thousands of dollars to a meeting with Bulger. After some sharp words from Bulger, the associate agreed to a prompt repayment. But the associate wanted to leave the meeting with some dignity. He told Bulger that after the debt was paid, he would run his own business, however he chose to run it.

"You are going to go your own way?" O'Brien recalled Bulger saying. "You know, we have a business besides bookmaking. And (the associate) said, 'What's that?' And Mr. Bulger said, 'Killing a..holes like you.'"

Over the opening three days of his trial, Bulger's expression, when visible to the public, has been something between bored and distracted. O'Brien's crack made him laugh, although it was not clear why.

O'Brien and another retired bookmaker, James J. Katz, gave hours of testimony that supported the government's contention that Bulger was part of a racketeering conspiracy that used threats and violence to extort millions of dollars of rent payments from dozens of bookmakers for more than three decades, beginning in the 1970s.

He is accused in the indictment against him of collecting millions more by extorting payments from drug dealers. He is accused of laundering the money in real estate or using it to bribe law enforcement officers. He is charged additionally with participating in 19 murders, four of which were part of the gang's attempt at a hostile takeover of the parimutuel business World Jai Alai in the early 1980s.

Throughout much of the period covered by the indictment, federal prosecutors said that Bulger and his longtime partner, Stephen Flemmi, were FBI informants, providing information about their rivals in the Mafia. A state law enforcement witness has testified that the local FBI office regularly protected the two by sabotaging investigations by other agencies.

Bulger denies being an informant and specifically denied involvement in half a dozen of the murders — those of two women and four victims of the jai alai takeover. But his defense team started speculation about strategy when it conceded to the jury in its opening statement that Bulger sold drugs, extorted millions in payments and was involved in illegal gambling.

Katz and O'Brien became reluctant witnesses after they were arrested under a plan developed in the early 1990s by the Massachusetts State Police and the U.S. Drug Enforcement Administration.