An update on a big story you saw here on Crime Watch Daily: Our Jason Mattera went behind bars with New York's so-called "Grid Kid Killer" John Giuca, serving time for the murder of a popular high school football star in 2003.

For the first time ever, a private investigator reveals he has new evidence, and he hopes it will get Giuca out of prison.

John Avitto is the man whose allegedly false testimony played a major role in putting John Giuca behind bars.

"He did lie on the stand during the trial, which basically convicted John Giuca," said private investigator Jay Salpeter.

Now John Avitto's emotional recantation of that testimony could set Giuca free in a pivotal court hearing going on right now. Avitto admitted on the stand to lying at trial.

"He got on the stand. He cried. He said he put an innocent man in jail to help himself," said Salpeter.

And Salpeter, a former New York city detective turned private eye who persuaded Avitto to recant is hoping it will right a wrong, and rewrite the story of one of the most controversial murder cases in New York criminal history.

"If his conviction is vacated then I'll be dancing in the street," said Salpeter.

So will John Giuca, who's been proclaiming his innocence from behind bars for more than a decade now.

"I'm in prison because I had a party, really," said Giuca.

Crime Watch Daily met with Giuca at the Clinton Correctional Facility in upstate New York for an exclusive prison interview, investigating charges that he got a bum rap.

"There's so many nights, if I go back and think, if I just hadn't had that party I wouldn't be here," said Giuca.

There were about 15 guests at that party at Giuca's Brooklyn home while his parents were out of town. Most of them were a close group of neighborhood friends who called themselves "The Ghetto Mafia." But one of them was a stranger: Mark Fisher, who accompanied a college classmate named Angel DiPietro.

And several hours after the party ended, Fisher, a strapping football star, was found lying dead in a driveway three blocks away at 6:40 a.m. with five bullets sprayed into his face and chest.

"I had nothing to do with this crime," said Giuca. "I did not murder Mark Fisher. All I did was have a party that night, and now I'm in prison for 25 years to life for something I didn't do."

Giuca claims he was at home asleep at the time of the murder, and that the last he saw of Fisher was when he gave him a blanket and let him sleep on a couch.

"I had nothing to do with his death," said Giuca.

But the prosecution convinced a jury that Giuca had given a gun to fellow Ghetto Mafia member Antonio Russo and ordered him to rob and execute Fisher. Russo was also sentenced to 25 to life as the trigger-man.

"Three people testified against me and recanted their statements and admitted they lied and were coerced and threatened into lying," said Giuca.

And John Avitto is the latest to recant his original testimony against Giuca, whom he met behind bars while they were both awaiting trial, Avitto on burglary and drug charges.

"The district attorney offered him his get-out-of-jail card and he played them like a professional card player," said Salpeter.

Allegedly in return for avoiding up to seven years in prison on a probation violation, Avitto told the district attorney's office he had heard Giuca confess to ordering the execution of Mark Fisher while they were in jail together.

After confessing at Giuca's current hearing that he made it up, Giuca's eyes welled up as Avitto addressed him directly and apologized.

And Giuca's mother, Doreen Giuliano, who adopted another identity, hid a tape recorder in her low-cut blouses and went undercover to get a juror in Giuca's trial to admit he had it in for her son from the beginning, praised Avitto for coming forward.

"I give the man a lot of credit. It took a lot of courage," said Giuliano.

Private investigator Salpeter also praised Avitto.

"He wanted to make amends for his life, for doing something wrong, and he wanted to bring John Giuca home," said Salpeter.

Now the prosecutors in Giuca's original trial have been accused by his attorneys at the current hearing of withholding important evidence and misleading jurors by saying Avitto received nothing in return for his testimony.

"That whole thing was a lie and the district attorney's office must have known it," said Salpeter. "They can deny it all they want. There's court records."

And Jay Salpeter is optimistic the judge will rule in John Giuca's favor.

"He has the option to deny us, he has the option of freeing John Giuca, overturning the conviction, or he has the option of giving us another trial," said Salpeter. "So we'll take two of three."

Giuca and his lawyers are due back in court for closing arguments on his appeal. After that, the judge is expected to rule some time later this summer on whether or not Giuca's conviction will stand.