By MICHAEL TARM

CHICAGO _ It seemed for a while as if R. Kelly's day in court might never come. But after six years of repeated delays, jury selection is set to begin Friday in the Grammy-winning R&B singer's trial on child pornography charges, prompted by a videotape allegedly showing Kelly having sex with a girl as young as 13.

Prosecutors, though, will have a unique challenge: The alleged victim, now 23, says it wasn't her. And Kelly's attorneys — including Ed Genson, who often represents the rich and famous — haven't admitted it's Kelly in the video.

"How is there not reasonable doubt when the two people say it's not them?" said Michael Helfand, a Chicago attorney not involved in the case.

But Helfand conceded that it's unclear what supporting evidence the prosecution might present.

The 41-year-old Kelly, whose first name is Robert, faces up to 15 years in prison if convicted. But Kelly — one of urban music's biggest stars, and a consistent hitmaker despite his legal woes — is glad the wait is over, his spokesman said.

"Every waking moment, he's always had this hanging over his head," spokesman Allan Mayer said. "He's confident that when all the evidence comes out he'll be shown not to be guilty of any crime."

The centerpiece of the trial is likely to be the video footage, which Judge Vincent Gaughan ruled may be shown in open court.

Prosecutors claim the videotape was made sometime between Jan. 1, 1998 and Nov. 1 2000, and that the girl was born in September 1984.

Kelly was indicted on pornography charges June 5, 2002, after the tape surfaced and was sold illegally on street corners and the Internet. Chicago police began investigating after receiving the tape from the Chicago Sun-Times, which said it was sent to the paper anonymously.

Police and prosecutors said their investigation, including interviews with about 50 witnesses, determined Kelly and an underage girl were on the tape, and that FBI forensics experts had determined the tape was authentic.

Prosecutors may need more than a videotape to prove their case, said Helfand, the Chicago attorney.

"I'd be beyond surprised if he got convicted based on what's out there," said Helfand.

It is unclear whether prosecutors have asked — or would be allowed — to tell jurors about accusations that Kelly allegedly had sexual relations with other minors, because some of the trial proceedings have been kept secret by the judge. Media outlets, including The Associated Press, have filed a legal challenge seeking to get court records and hearing transcripts unsealed.

Kelly has settled three lawsuits accusing him of having sex with underage girls, filed in 1997, 2001 and 2002. In the third suit, the woman claimed that she began having sex with Kelly when she was 16, and that he forced her to have an abortion.