Greensboro, North Carolina (CNN) -- A former campaign aide for John Edwards said in court Friday that he had been intimidated in his dealings with the former senator and two high-priced donors.
"I was scared for my life," Andrew Young testified in U.S. District Court in Greensboro, North Carolina. "I was up against two billionaires and a millionaire. I was scared. It was bizarre."
Prosecutors have argued that Edwards broke federal law by accepting about $725,000 from now-101-year-old heiress Rachel "Bunny" Mellon and more than $200,000 from Fred Baron, a Texas lawyer who has since died.
Young is considered the government's star witness against Edwards, a former Democratic senator and presidential candidate from North Carolina who is accused of using hundreds of thousands of dollars in donations to conceal his affair with a campaign videographer without reporting the money to federal authorities.
Edwards is facing six felony charges, including that he accepted illegal campaign donations. He also is charged with conspiracy and making false statements.
Edwards' attorneys have argued that Young had instead been involved in what was largely a ruse to extract hundreds of thousands of dollars from the donors for personal use.
During Friday's testimony, Young recalled a drive he took with Edwards in North Carolina in 2008. Edwards had learned that Young had received donations without his knowledge.
"I said if he won't tell the truth, I was going to tell the truth," Young told the court. Edwards responded, he said, "You can't hurt me, Andrew. You can't hurt me."
Young's testimony comes a day after he was hammered on the witness stand about his own motives and asked whether he made up stories about how Edwards concealed contributions from campaign donors.
The former aide said during cross-examination Thursday that "we lost our perspective," acknowledging he used donations for personal expenses at a California home. Young said he used the funds in constructing a pool and a theater.
Wednesday was the first day the defense cross-examined Young, and the attorneys focused mostly on apparent inconsistencies between Young's public statements and things he wrote in a book about the case.
For example, Young has described a time when Edwards returned home from a trip overseas with a phone purportedly given to him by his mistress, Rielle Hunter. Young said Edwards was asleep when the phone rang, and Edwards' wife, Elizabeth, answered.
Hunter began talking, assuming John Edwards was on the other end of the line.
Under cross-examination, Young admitted he had no firsthand knowledge of the story.
Defense attorney Abbe Lowell also questioned Young's assertion that Edwards refused to take a call from Hunter as she left for the hospital to have Edwards' baby, something Young described as "bone-chilling" in its disregard. Lowell pointed out Hunter later said Edwards had, in fact, called her.
Edwards is accused of concealing the money from the public and the Federal Election Commission, which polices political contributions, by filing false and misleading campaign disclosure reports.
Young is testifying for the prosecution under a cooperation agreement with the hope that he won't be prosecuted.
Edwards could face up to 30 years in prison if convicted of all six felony and misdemeanor counts against him.
Young is the author of the tell-all book "The Politician: An Insider's Account of John Edwards's Pursuit of the Presidency and the Scandal That Brought Him Down."
He testified that he wrote the book for two reasons: "It had been almost three years since Mr. Edwards promised me he would tell the truth, (and) we also very much needed the money."