The now-25-year-old man, identified as Victim 10, told jurors that he was in Sandusky's basement in 1998 when the "defendant pinned me to the ground and pulled my shorts down and started performing oral sex on me."
"I freaked out. I was scared," he said. "He told me that if I ever told anyone that I'd never see my family again."
Victim 10 said he was about 11 years old at the time of the alleged assaults and was living in a foster home. Sometime later, Sandusky allegedly assaulted him in a swimming pool.
"Mr. Sandusky came up from behind me in the pool and swam between my legs and put me on his shoulders and put his hand down the front of my swim trunks. Mr. Sandusky reached his hands up the front of my shorts and touched my genitals," he testified.
In another incident, the accuser said he was in Sandusky's car when the coach asked him to perform oral sex on him. When he refused, Sandusky threatened him again, and he then carried out the sex act.
Sandusky, 68, is charged with 52 counts of sex abuse involving 10 boys over a 15-year span. Three of Sandusky's accusers testified Wednesday, bringing to five the number of them to take the stand. Defense attorneys have suggested his accusers have financial motivations for coming forward.
Under cross-examination, the man admitted he had spent nearly two years in state prison for a robbery and had been involved with drugs and alcohol. But he added that he was doing better now.
"I'm married. I'm expecting" a child, he said.
The man referred to as Victim 7 said he was just 10 years old when Sandusky molested him in the coach's car, in a spare bedroom at the coach's house and at least six times in the showers at Penn State.
"I remember him trying to shampoo my hair, shampoo my back and shoulders, at which point I tried to slide down another shower to get away. When he did the bear hug in the shower, I don't remember him saying anything, just sort of grunting," he testified.
A third witness told jurors he was assaulted once, also in a shower.
Earlier Wednesday, John McQueary, the father of former assistant coach Mike McQueary, testified about a phone call he had with his son in 2001 after the former Penn State quarterback allegedly saw Sandusky assaulting a young boy in a locker room shower.
John McQueary said his son told him he saw Sandusky with a boy in the shower, but said when he asked his son detailed questions about whether he saw "penetration" or "sodomy," his son responded that he had not seen that.
"I asked him if he'd seen anal sex, said, 'Did you see anything that you could verify, penetration?' I might have used the word sodomy, and he said, 'no I did not actually see that,' and I said, 'so you did not actually witness penetration or anything?' and he said 'no,'" he said.
John McQueary told the court he approached former university vice president Gary Schultz about the allegations, and said Schultz told him he'd heard "noises" previously about Sandusky misconduct.
Schultz and the school's former athletic director face charges of failure to report suspected child abuse and perjury related to their grand jury testimony about Sandusky. Both maintain their innocence.
The judge has told jurors that the prosecution is expected to rest by Friday.
ABC News and The Associated Press contributed to this report.