CHICAGO (NYTIMES) - A woman has identified herself and R. Kelly as the people in an old videotape that American prosecutors said showed the R&B singer engaging in sex acts with an underage girl.

In 2008, a jury in Chicago declared Kelly not guilty of producing child sexual abuse imagery after seeing the infamous video.

The defence team had argued that the identities of the people in the tape were in question, and several jurors said the lack of testimony from the victim was a significant barrier to convicting Kelly.

But on Thursday (Aug 18), the woman at the centre of the 2008 trial took the stand, saying that she and Kelly had sex "hundreds" of times when she was underage, and explaining how two decades ago, he had persuaded her to deny their relationship to law enforcement officials.

"I was extremely scared that my parents would find out," she said, adding that she was afraid of what would happen to Kelly.

Kelly, whose full name is Robert Sylvester Kelly, has been trailed by accusations of abusing young women and underage girls for more than two decades.

The 55-year-old artiste had long avoided criminal punishment until last year, when he was sentenced to 30 years in prison after he was convicted in federal court in New York of racketeering and sex trafficking charges.

Before that, the 2008 trial was the closest Kelly had gotten to being held accountable.

The woman at the centre of that trial, now 37, took the stand at the Everett M. Dirksen United States Courthouse in downtown Chicago, where she said that she had been repeatedly sexually abused as a teenager by Kelly.

She testified that it was, in fact, her at age 14 appearing in the videotape, which at one point shows Kelly urinating on her.

Testifying under a pseudonym for more than four hours on Thursday, the woman told the court that in 2002, after law enforcement officials had obtained the tape, Kelly sent her and her parents out of the US to make them inaccessible to investigators.

The I Believe I Can Fly (1996) singer then urged her to deny to a grand jury that it was her on the tape and paid for a lawyer to accompany her, she said.

She testified that she had falsely told the grand jury that it was not her on the videotape and that she was not sexually involved with Kelly.

She said that she gave Kelly's lawyers a necklace of hers that could be seen on the videotape.

As the woman spoke, Kelly - who is facing charges of coercing minors into sex, receiving child sexual abuse videos and conspiring to obstruct justice - remained impassive.

The woman told the jury that she was 13 years old when she was first introduced to Kelly by her aunt, a protegee of Kelly's who goes by the stage name Sparkle.

Kelly, who became the woman's godfather, started speaking sexually with her over the phone, she said, then started abusing her physically.

She testified that Kelly would sexually assault her at various locations, including his home, the recording studio and his tour bus.

The tape surfaced after Mr Jim DeRogatis, a journalist for The Chicago Sun-Times who had reported on the accusations against Kelly, received it in the mail from an anonymous sender, and turned it over to law enforcement.

Kelly was charged in 2002 with producing child pornography, and he stood trial in 2008 but was acquitted.

The woman testified that around the time of the trial, she was living with Kelly in his mansion, and that after he was acquitted, he began physically abusing her and controlling her ability to leave.

He later helped her move into her own place and get a car, she said.

A lawyer for Kelly, Ms Jennifer Bonjean, who is expected to cross-examine the woman on Friday, sought to undermine her testimony in opening arguments, telling the jury that she has an immunity deal with prosecutors.

The woman affirmed that in exchange for her testimony, prosecutors had granted her immunity from prosecution for perjury related to the false grand jury testimony in 2002.

Prosecutors say that they now have more evidence of the woman's abuse than the state prosecutors had 14 years ago.

The 2008 trial focused on one video, but the current trial centres on four videos that prosecutors say show Kelly sexually abusing the woman.

Those videos are the basis for charges against Kelly related to producing child pornography, as well as the ones related to receiving child pornography.

According to the federal indictment, Kelly and his associates realised in 2001 that videotapes of him sexually abusing the woman were missing, and as a result, they began a multi-year effort to recover the tapes, paying one person hundreds of thousands of dollars to try to regain possession of them.

Charges against two of Kelly's associates, Derrel McDavid and Milton Brown, who are standing trial at the same time as Kelly, relate to accusations that they had tried to find the missing tapes.

Both men pleaded not guilty, and their lawyers have argued that they were carrying out their jobs, unaware that Kelly was abusing children.

Later on in the trial, four other women are also expected to testify that Kelly sexually abused them when they were girls.