CHICAGO (AP) — R. Kelly's lawyers opened his defence, calling relatives of the alleged victim to testify that she's not the person in the sex video at the center of the case.

Another defence witness on Wednesday accused a key prosecution witness of soliciting $300,000 from the R&B superstar in exchange for her silence.

So far, seven family members of the alleged victim have testified — four prosecution witnesses who said earlier that they recognised the woman, and three who said Wednesday that they did not.

"It definitely wasn't her," said Shonna Edwards, when asked Wednesday whether the underage girl seen having sex with the Grammy winner on the video was her relative.

The 27-year-old Edwards said she saw the tape for the first time several days ago in a lawyer's office, telling jurors that the female's body in the tape was too developed to be her relative at that time.

Prosecutors, who rested their case Monday, allege the girl was as young as 13 when the tape was made.

Edwards also said she met Kelly frequently in the 1990s when she sang in an R&B music group with her relative, and she added that the man in the sex tape "did not appear" to be Kelly.

Kelly, 41, is charged with 14 counts of child pornography for allegedly videotaping himself having sex with an underage girl.

He has pleaded not guilty and faces up to 15 years in prison if convicted.

Both he and the alleged victim deny they're on the graphic, 27-minute tape.

The singer, dressed in a honey-brown suit and bright flower-pattern tie, appeared attentive as he sat behind the defence table Wednesday, sometimes even nodding his head in agreement during the testimony for the defence.

During cross-examination, prosecutors displayed two photos on a split screen — one of the female in the tape and one of the alleged victim — and asked Edwards if it was at least possible they were the same person.

"Not at all," Edwards said without hesitating.

Other relatives, Charlotte Edwards and Leroy Edwards Jr., provided similar testimony on Wednesday. When prosecutors pressed Leroy Edwards Jr. about whether the alleged victim's family "has pretty much split in half as a result of this incident," he answered softly, "Yes."

Also Wednesday, the defence sought to discredit the testimony of a star prosecution witness, Lisa Van Allen, who told jurors Monday that she engaged in three-way sex with Kelly and the alleged victim.

A law clerk for the defence team, Jason Wallace, told jurors that Van Allen's fiancé, Yul Brown, sought $300,000 from Kelly in return for a promise not to testify against him.

"Lisa doesn't have to testify in court if things are made right," Wallace quoted Brown as saying during a meeting with a Kelly attorney in Georgia last month, according to Wallace.

Van Allen was at the meeting in a hotel lobby, Wallace said, but Brown did all the speaking. But Wallace said Van Allen kept nodding her head in agreement.

Under cross-examination, prosecutor Robert Heilingoetter accused the defence of "trying to create an illusion of impropriety" around Van Allen's testimony.

Earlier Wednesday, a Chicago Sun-Times reporter declined to answer questions at the trial.

After he was sworn in, Jim DeRogatis cited an Illinois law that governs reporters' rights and the First and Fifth Amendments of the U.S. Constitution in refusing to answer questions.

DeRogatis received the sex tape through the mail in early 2002 and then turned it over to authorities. Prosecutors charged Kelly later that year based on the tape.

DeRogatis read his statement off an index card more than a dozen times in response to questions, including to whether he once made a copy of the sex tape. Defence attorneys have said that copying the tape would have been a crime.

After DeRogatis spent 10 minutes on the stand, Judge Vincent Gaughan said that the First Amendment and other reporters' privileges don't apply in this case.

But he ruled that DeRogatis doesn't have to testify based on his Fifth Amendment rights against self-incrimination.

DeRogatis attorney Damon Dunn argued that reporters have an obligation to pursue facts and that "they shouldn't be put in this type of position by defendants."

He added that DeRogatis continued to cover the R. Kelly case.

Dunn said covering child pornography has "higher societal goals".

He also argued that if forced to testify DeRogatis won't be able to guarantee to sources in the future that he would not have to reveal their names.

But defence attorney Mark Martin said the defence didn't intend to ask DeRogatis about his sources.

"So reporters' privilege does not apply. ... Being a reporter does not give a reporter rights to commit criminal offences," Martin said.