In 2008, he was near tears as he told a judge: "I didn't mean to steal anything from anybody ... I'm sorry. I'm sorry for all of it."
This time he will get to say much more testifying for at least a day about a strange Las Vegas hotel room confrontation that sent him to prison.
There is no jury and his fate will be determined by Clark County District Judge Linda Marie Bell.
"He's been wanting to tell his story. He's excited about telling his story," said Simpson attorney Ozzie Fumo.
When he went to trial in 2008 on charges of armed robbery and kidnapping, Simpson did not testify - a decision that one of his lawyers said was pushed upon him by another attorney he trusted so completely that he took his bad advice.
"It's going to be a long day," said his co-counsel, Patricia Palm, "He's going to have to testify to every point in the petition. But they can't do a little mini-retrial."
With 19 points raised to support reversal in the writ of habeas corpus, Simpson will answer many questions from his lawyers and then undergo cross-examination by an attorney for the state who wants to keep him in prison.
"He is anxious, and it's hard for him when he hears testimony that he wants to refute," Palm said of the 65-year-old former football hall of famer.
Simpson is testifying midway through a five-day evidentiary hearing. He's serving nine to 33 years in prison for his conviction on armed robbery, kidnapping and other charges in a 2007 gunpoint confrontation. Simpson has said, and is likely to repeat, that he never saw any guns.
Attorney Gabriel Grasso was Simpson's star witness, the Las Vegas lawyer who joined the case when his old friend, Yale Galanter, called and said, "Hey Gabe, want to be famous?"
He said he soon realized he would be doing most of the behind the scenes work while Galanter made the decisions.
"I could advise O.J. all day long, and he was very respectful of me," Grasso told the court. "But if I advised him of something different from what Yale said, he would do what Yale said."
It was Galanter's decision not to have Simpson testify, Grasso said.
Under questioning from H. Leon Simon, attorney for the state, Grasso acknowledged the trial judge, Jackie Glass, specifically asked Simpson if he wanted to testify and he said no.
"Mr. Galanter told him, 'This is the way it's going to be,'" Grasso said, adding he would have put him on the stand.
He said Simpson's confidence in Galanter was born of the acquittal he gained for the former Hall of Fame football player in a road rage case in Florida five years after his 1995 acquittal on murder charges in the deaths of his ex-wife, Nicole Brown Simpson, and her friend, Ronald Goldman.
Galanter is now the focus of Simpson's motion claiming ineffective assistance of counsel and conflict of interest. He has declined to comment until he takes the stand Friday.
There are questions of money too. Grasso accused Galanter of lining his own pockets while telling him they were "operating on a shoestring" and couldn't afford to hire expert witnesses. Simpson's business attorney, Leroy "Skip" Taft testified by phone Tuesday that he kept getting big bills from Galanter but no explanation of what costs were eating up hundreds of thousands of dollars.
Witness after witness spoke of a proposed plea bargain that Galanter turned down on Simpson's behalf but no one was sure the defendant knew about it.
There were rumours that Galanter gave his blessings to Simpson's plan to show up at a hotel room and reclaim his memorabilia, which two dealers were trying to peddle.
Retired Clark County District Attorney David Roger, who prosecuted Simpson, was asked whether investigators determined if Galanter helped Simpson plan the 2007 hotel room confrontation.
"He said he did not advise Mr. Simpson to commit armed robbery," Roger said.
"And he said he wasn't there?" Fumo asked.
"Yes," Roger replied.
Others have testified that Galanter was in Las Vegas and had dinner with Simpson the night before.
The other prosecutor, Chris Owens, testified about discovering phone calls between the two but hiding that fact from the judge. He identified at least 10 calls in the days preceding and on Sept. 13, 2007.
Both prosecutors described an agreement with the Simpson defence that was read to the jury saying there were no calls.
"So you stipulated to events that weren't true?" Fumo asked Owens.
"It was in the form of a legal construct," Owens replied and said Judge Jackie Glass encouraged it because she didn't want to confuse the jury with another issue.
This is Simpson's last chance under state law to prove that he was wrongly convicted. A federal court appeal is still possible.
But Simpson has aged rapidly and his changed appearance - heavy, greying and shuffling under the weight of shackles - has shocked friends and relatives who travelled to Las Vegas to see him.Suggest a correction