A 29-year-old Clinton County man who says he is at the center of a lingering mystery from Jerry Sandusky's 2012 child sex-abuse case is set to testify for the first time Friday as part of the former Pennsylvania State University football coach's bid for a new trial.

Sandusky's lawyers believe the man is Victim 2, the boy whom graduate assistant Mike McQueary saw sexually assaulted by Sandusky in a campus locker-room shower in 2001. What's more, they say, prosecutors hid him from jurors at the trial four years ago because his account didn't match that of their star witness.

Those prosecutors say the man is an impostor who, with the help of a civil attorney, molded his story to position himself for the largest possible payout from Penn State.

Despite the dramatic potential at Friday's hearing in a Bellefonte courtroom, Senior Judge John M. Cleland has said he has no interest in settling once and for all whether the man truly was that boy Sandusky assaulted in the shower.

Instead, the judge has directed Sandusky's lawyers to limit their focus to what prosecutors believed at the time and if, as they assert, lead prosecutor Joseph McGettigan hid the truth and lied to jurors by telling them the identity of Victim 2 was "known only to God."

But the prospect of his public testimony has drawn wide interest, five years after the story of Victim 2 forced a football-focused campus to reevaluate its culture and the legacy of some of its greatest heroes.

More than any other allegation in Sandusky's case, McQueary's account of what he saw in that shower - and how others responded - changed the scandal from one focused on a lone serial predator to a story about institutional failures.

It ultimately led to the firing of Penn State's iconic football coach, Joe Paterno, the still-pending prosecution of three top administrators for allegedly covering up Sandusky's crimes, and the unprecedented $2.4 million fine imposed on the university Thursday by the U.S. Department of Education.

Sandusky, 72, has said he is certain the man set to testify Friday is the same person described in the presentment. Though the former coach is unlikely to take the witness stand Friday, he is scheduled to appear with his lawyers at the proceeding, a continuation of an appeal hearing that began in the summer. In addition to his allegations regarding Victim 2, Sandusky is seeking a new trial, claiming prosecutorial misconduct and that his trial lawyers provided a woefully ineffective defense.

State investigators maintain they still don't know the identity of the boy in the shower, but McQueary has testified several times that he reported the child's abuse in 2001 to first Paterno and later to Tim Curley, the school's athletic director, and vice president Gary Schultz. Neither man informed the police or child welfare authorities at the time, and they now face child-endangerment charges, along with former Penn State president Graham B. Spanier.

The man set to testify Friday, whose name the Inquirer has withheld because of his allegations, was among the 32 Sandusky accusers who have received settlements from Penn State. But he has a troubled history as a potential witness, one that could impact both sides.

A Marine veteran, he has told investigators that, like the other victims, he met the ex-coach through Sandusky's charity for troubled youth, the Second Mile, and soon found himself invited to Penn State football games and sleepovers at Sandusky's house.

He grew up alongside many of the accusers who eventually testified at Sandusky's trial. Unlike them, however, his relationship with the man extended well into adulthood. He attended the funeral of Sandusky's mother, lived with the coach for a time while attending college, and invited Jerry and Dottie Sandusky to his wedding.

When rumors began swirling in early 2011 that Sandusky was the target of a grand jury investigation, the man told state investigators the coach had never touched him inappropriately and, at Sandusky's urging, wrote a letter of support to the Centre Daily Times.

"He has been a best friend, tutor, workout mentor and more," the letter said. "We've worked together, competed together, traveled together and laughed together."

When Sandusky was charged later that year, the man agreed to testify for the defense, telling Sandusky's lawyers that he had been the boy in the shower, that he remembered seeing McQueary that night in 2001 - and that nothing untoward had occurred.

But within a month, the man had retained a civil attorney and his story changed again.

His lawyer, Andrew Shubin, testifying at a hearing in the summer, said that he never doubted his client was the Victim 2 described in Sandusky's presentment but felt that prosecutors were never interested in him as a witness.

Investigators say they had reasons for their doubt. Several times between February and May 2012, the man gave conflicting accounts of abuse.

First, he told investigators that Sandusky had abused him only on three out-of-town trips. Later, he said the former coach abused him only in Penn State's athletic building, where he claimed to have been sexually assaulted 10 times.

He never detailed the attacks, saying they were too difficult to discuss and he could not say when the abuse started, according to an April 2012 memo filed by Anthony Sassano, the lead investigator on the Sandusky case.

And when McQueary altered his own testimony - saying the incident he witnessed did not occur in 2002, as he had originally stated, but rather in 2001 - the man's story shifted with him.

"He was not credible," Sassano has said in past court hearings. "We all arrived at the same conclusion."

McGettigan, the trial prosecutor, had his own concerns. Asked during a hearing before Cleland in August if he believed the man's shower-assault claim, McGettigan responded brusquely: "I did not then. I do not now."

Born in 1987, the man would have been 14 at the time of the alleged assault, McGettigan said. The boy McQueary described was 8 to 10 years old.

And when asked by investigators to draw the layout of the locker room where he alleged he had been attacked, the man produced a sketch that bore no resemblance to the room where McQueary said he witnessed the sexual assault.

Still, Sandusky's appellate lawyers believe he is key to proving prosecutorial misconduct and unraveling Sandusky's conviction, four years after the coach was sentenced to a 30-to-60-year prison term.

In court filings earlier this year, they contended that in an interview with their investigator, the man recanted his claims of abuse, reverting to his earlier statement that Sandusky never touched him.

The man who says he is Victim 2, they claim, has changed his story again.

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