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Attorneys for R. Kelly are challenging an expert witness in the R&B star’s child pornography case. At a Friday hearing at the Cook County courthouse, Kelly’s lawyers filed a motion to keep prosecution expert Dr. Sharon Cooper off the stand in the yet-to-be-rescheduled trial, Assistant State’s Atty. Shauna Boliker said.

Cooper, a developmental and forensic pediatrician, is expected to testify as to the age of the girl featured in the videotape that resulted in 14 charges of child pornography against Kelly, Boliker said. The videotape allegedly portrays Kelly engaged in sex acts with a girl prosecutors say could have been as young as 13 at the time of taping.

Cooper is expected to testify that the girl’s hesitant behavior and denial is typical of victims of child pornography, the Tribune reported. Cooper also is expected to point out similarities between vein patterns on the hand of the man depicted in the video and those on Kelly’s hand in Chicago police photos, according to the Tribune.

No new trial date has been set in the case. Kelly is due back in court Nov. 2, Boliker said. Kelly, who appeared at Friday’s hearing, has pleaded not guilty to all of the charges.