"If you were pretending you were asleep and you were touched or rubbed in some way, you could just act like you were rolling over in your sleep, so that you could change positions," Matt Sandusky said in an excerpt of the tape. His attorneys confirmed the recording's authenticity to The Associated Press.
Jerry Sandusky was convicted last week of 45 counts of abusing 10 boys he met through the charity he founded, the same organization that introduced him to Matt Sandusky, who became his foster child.
Jerry Sandusky's principal lawyer did not return messages Tuesday, and another lawyer said only that Matt Sandusky's allegations contradict testimony he gave to the grand jury whose charges put his father on trial.
Matt Sandusky did not reveal any abuse when he was initially questioned as a grand jury witness but did release a statement alleging past abuse as the jury was sequestered in deliberations last week.
The police interview tapes are the first time Matt Sandusky's allegations of sexual abuse have been publicly aired, and too much time has passed for criminal charges. Asked why he was now coming forward on abuse purported to have occurred as early as the late 1980s, Matt Sandusky told police there were several reasons - but singled out his family.
"So that they can really have closure and see what the truth actually is. And just to right the wrong, honestly, of going to the grand jury and lying," he said in the police interview.
Jerry Sandusky hasn't been charged with abusing Matt, one of six children adopted by the former coach and his wife, Dottie. Messages left for Sandusky's other children were not returned.
Matt Sandusky sat with Dottie Sandusky on the first day of the trial but left after hearing one of the accusers testify. His attorneys have said he reached out to them while the trial was under way, saying he wanted to talk to prosecutors.
Matt Sandusky said that he was undergoing therapy and that his memories of abuse were only now surfacing. He said on the tapes that he tried to flee Sandusky's house and also attempted suicide.
"I know that I really wanted to die at that point in time," he said.
On the recording, Matt Sandusky says he was sexually abused off and on between ages 8 and 15. While being questioned, he said Jerry Sandusky would blow raspberries on his stomach and touch his genitals. The acts described were similar to accounts relayed by eight accusers who offered graphic testimony on the witness stand.
The Associated Press contributed to this report.
