Although neither victim could identify the gunmen because they said they were told not to look at them, DNA that Gadson was required to submit to police after being arrested for robbery in the early 2000s eventually linked him to the 1998 assault.
Gadson, 37, of 43rd Street near Brown, in West Philadelphia, was formally arrested in January 2010.
His defense attorney, James Ephraim Lee, told the Common Pleas jury of seven men and five women that his client and the female victim had engaged in consensual sex.
Lee argued during the weeklong trial that the girl told police she had been raped because she needed an excuse for getting home late and missing her grandmother's curfew. Her boyfriend was not even in the park at the time of the encounter but he went along with her lie, said Lee, who said he plans to appeal.
He said reasonable doubt abounded in the case, including that only Gadson's DNA was recovered from the victim, though she and her husband testified that there were two rapists.
The jury, which began deliberating Monday morning, didn't buy that defense. Instead, it was the case put on by Assistant District Attorney Kelly Harrell that carried the day with the jurors.
She argued that Gadson and his still-at-large accomplice had committed a brutal, gunpoint stranger rape.
The jury convicted Gadson, a father of five, of rape, sexual assault, robbery, unlawful restraint and conspiracy.
Gadson, who was found not guilty of a handgun charge, faces a possible maximum state prison term of 30 to 60 years when he is sentenced May 16.
"I will probably be asking for something close to the maximum because that's something he deserves after the nature of this crime," Harrell said. "It's the stranger rape of a teenage girl at gunpoint while her significant other was held down."
Judge Giovanni O. Campbell revoked Gadson's bail and had him taken into custody.
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