Six years after R&B singer R. Kelly’s indictment on child pornography charges, his lawyers revealed the linchpin of their defense: A mole.

On Tuesday, the first day of testimony, jurors saw police photos that revealed a dark, caterpillar-shaped mole in the middle of Kelly’s lower back. But defense lawyer Sam Adam Jr. told jurors the sex videotape at the center of the case shows a man without a mole.

“Robert Kelly is not on that tape,” Adam said in his opening statement. On the tape, the man’s “back is illuminated, and there is no mole.”

Prosecutors allege Kelly made a 27-minute tape eight to 10 years ago that shows him having sex with a girl as young as 13. He has pleaded not guilty.

“This case is about child pornography that was created, staged, produced and starred in by Robert Kelly,” said Assistant State’s Attorney Shauna Boliker.

“It will unfold before you, frame by disgusting frame,” she said as Kelly looked at jurors, his brow furrowed.

One person who did not view the tape Tuesday is a rape victim who was selected as a juror last week. Cook County Judge Vincent Gaughan excused the woman after she claimed serving would be an economic hardship.

Adam outlined a double-barreled strategy for the defense — that it’s not Kelly on the tape, and that the girl is not who prosecutors say she is.

The defense lawyer hammered at what some see as a weakness in the prosecution’s case: that the girl, now 23, will not testify she was in the tape.

“She’s right here in the city. Right here on the South Side of Chicago,” Adam said. “Now, why wouldn’t they bring her in?”

Adam called the alleged victim “a wonderful person,” and noted the girl on the tape receives money. “The woman on that tape, paid with money — she is a prostitute,” Adam said.

Adam also said the alleged victim’s mother will not testify for the prosecution. The girl herself could testify for the defense, court documents show.

Earlier, the defense filed a motion to subpoena Sun-Times pop music critic Jim DeRogatis, who was sent the tape anonymously in 2002 and turned it over to police. Gaughan said he would take up the issue Friday.

Defense lawyer Ed Genson asked retired Chicago Police detective Dan Everett if he was aware DeRogatis had written articles critical of Kelly. Everett replied no, but said DeRogatis had previously given police another alleged Kelly tape.

Contributing: Abdon M. Pallasch