An unidentified woman will reportedly testify in R. Kelly's trial that she had a threesome with the Chicago bred crooner and an underage girl.

As reported earlier, Kelly is facing multiple child pornography charges for allegedly making a sex tape with a teenage girl who is currently in her 20's.

The Chicago Sun-Times reports that a source close to the case revealed that the unidentified woman will testify that he had sex with Kelly and the girl in the tape that would have between 13-14 years old at the time.

“She was involved in a threesome with (the girl) and R. Kelly,” the source said.

The girl in the center of the tape is also expected to take the stand during the trial but she will reportedly testify that she is not in the tape.

The trial is expected to start next Friday.