Story highlights NBC News obtains audiotape of police interview with Matt Sandusky

Matt Sandusky was willing to be rebuttal witness in trial of his adoptive father

Jerry Sandusky decided not to testify in his own defense

Now convicted, he remains under suicide watch at jail

Matt Sandusky stood in solidarity with his adoptive father, Jerry Sandusky , while a grand jury investigated multiple allegations of child rape against the former Penn State assistant football coach.

Matt Sandusky told the grand jury nothing inappropriate had ever happened to him. And he sat with the rest of the family early in Jerry Sandusky's recent trial.

But last week brought a bombshell that shook the proceedings: Matt Sandusky, 33, was now willing to testify that the man he first met through the Second Mile charity repeatedly molested him while he was a child, according to Matt Sandusky's lawyers. The revelation kept Jerry Sandusky from taking the stand in his own defense.

Portions of a 29-minute interview police had with Matt Sandusky during the middle of the trial were broadcast Tuesday on NBC, which obtained the audiotape. Jurors never heard the tape.

Detectives asked Matt Sandusky why he was now willing to cooperate.

JUST WATCHED Attorney talks what's next for Sandusky Replay More Videos ... MUST WATCH Attorney talks what's next for Sandusky 06:19

JUST WATCHED Joe Amendola: Sandusky wanted to testify Replay More Videos ... MUST WATCH Joe Amendola: Sandusky wanted to testify 06:17

JUST WATCHED Matt Sandusky was prepared to testify Replay More Videos ... MUST WATCH Matt Sandusky was prepared to testify 04:49

JUST WATCHED Did Jerry Sandusky molest his son? Replay More Videos ... MUST WATCH Did Jerry Sandusky molest his son? 02:50

"I mean for my family so that they can really have closure and see what the truth actually is," Matt Sandusky said. "And just to right the wrong, honestly, of going to the grand jury and lying."

In the police interview, Matt Sandusky said that he was molested between the ages of 8 and 15, that he tried to escape from the Sandusky home and once attempted suicide.

"I know that I really wanted to die at that point and time," he said, according to the audio obtained by NBC News.

Matt Sandusky, a foster child formally adopted at 18, also described Jerry Sandusky rubbing, hugging and showering with him.

"If you were pretending you were asleep and if 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," said Matt Sandusky. The defendant would sometimes rub near and against his genitals, he told police.

The potential witness said he could not recall penetration or oral sex.

It was only days before the commonwealth rested, and after some alleged victims had testified, according to Matt Sandusky's lawyers, that he told them he was abused and wanted to cooperate with prosecutors.

The younger Sandusky's willingness to testify as a rebuttal witness created a dilemma for Jerry Sandusky's defense team.

They wanted their client to testify after the jury heard damning testimony from eight alleged victims, but they decided it against it.

"To put Jerry on the stand and have Matt come in and testify against him it would destroy any chance of an acquittal," co-defense counsel Joe Amendola told reporters Friday night after his client was convicted of 45 of 48 sexual abuse charges against him.

Amendola said that Jerry Sandusky, 68, denied ever having inappropriate contact with Matt.

By not putting Jerry Sandusky on the stand, the defense ensured that Matt Sandusky would not testify.

The younger Sandusky's attorneys, Justine Andronici and Andrew Shubin, released a statement about the recording.

"This tape demonstrates Matt's tremendous courage and strength as he begins to disclose that Jerry Sandusky sexually abused him when he was a child," they said. "Although the tape was released without Matt's knowledge or permission, it illustrates that he made the difficult decision to come forward and tell the painful truth to investigators despite extraordinary pressure to support his father."

The audiotape's leak was the main subject of a meeting hastily called Tuesday by trial Judge John Cleland and attended by prosecutors, defense attorneys and even the judge who has overseen the grand jury that's investigated the Sandusky case, a source with knowledge of the meeting told CNN National Correspondent Susan Candiotti.

No one at the meeting took responsibility for sharing the tape with the media, the source told CNN. Jerry Sandusky's defense team was asked to turn over its copy of the tape, but it will remain available to them.

Cleland ordered that any discovery turned over to the defense in the Sandusky case be sealed unless it was put into evidence at trial. He also said defense attorneys shall give a sworn statement within 10 days as to what materials they received and who they have given it to.

The judge is trying to protect the current investigation and the privacy of the victims and witnesses.

Neither prosecutors nor defense attorneys, who have vowed an appeal, would comment on Tuesday's meeting.

Matt Sandusky's grand jury testimony remains a secret. Amendola said months ago he was not concerned about what the man said before the grand jury.

Karl Rominger, another defense attorney, had a jailhouse visit with Jerry Sandusky on Monday.

"I'm innocent," said Jerry Sandusky, in answer to questions CNN's Candiotti asked of him through his lawyer. "I didn't do it," he said, according to Rominger.

Rominger says Sandusky was bothered he didn't get to testify. But Jerry Sandusky doesn't regret his decision, according to his lawyer.

Sandusky, who was allowed Monday to call his wife, Dottie, is not allowed visitors until a psychiatric examination is completed that also will determine whether he remains on suicide watch, according to Rominger.

"Some of the guards are friendly and will talk with him. Others don't talk to him at all," according to Rominger.

Sandusky is allowed out of the small cell -- which features a toilet, sink and bed -- once a day to take a shower.

"He's come up with exercises to keep active," his lawyer told CNN. "Enough to work up a sweat."