The 41-year-old singer is accused of allegedly videotaping himself having sex with a girl as young as 13 years old.
The star witness was briefly mentioned during testimony yesterday. Kelly's former assistant told the jury that the woman and the girl were regulars at the singer's performing studio in the late 1990s. She also testified that the she is 110 percent certain that Kelly is the man in the tape.
Kelly denies that he is the man on the videotape. The girl allegedly in the video -- now an adult -- is expected to tell the court she is not on the tape either.
Last week, eight prosecution witnesses identified the girl and claimed she was 13 or 14 at the time the tape was made.
Defense attorneys have tried to poke holes in that testimony by asking witnesses how they can be sure Kelly and the alleged victim are on the graphic, 27-minute video.
In testimony Tuesday, a recent employee of Kelly testified she didn't want to believe at first that the R&B superstar appears on the tape because he'd been such a good boss. But she told jurors she's now sure it's him.
Another witness sounded less sure. He said those in the video "favored" the images of Kelly and the alleged victim.
Kelly has pleaded not guilty to 14 counts of child pornography.
The Associated Press contributed to this report. All rights reserved.