CHICAGO The judge presiding over singer R. Kelly’s child pornography trial ruled Friday that Chicago Sun-Times pop music critic Jim DeRogatis must testify in the case.

In 2002, someone sent DeRogatis the videotape that allegedly shows Kelly having sex and urinating on an underage female. DeRogatis turned the tape over to the police, beginning the investigation into the star.

Kelly’s attorneys had asked Cook County (Ill.) Judge Vincent Gaughan to order DeRogatis to testify, saying it would be crucial to their defense.

In court Friday, Sun-Times attorney Damon Dunn argued that the Illinois reporter’s shield law and the First Amendment protecting DeRogatis from being forced to testify, the Sun-Times reported in its “Kelly’s Chronicles” blog about the trial.

The blog entry, written by Kim Janssen, said Dunn vowed outside the Criminal Courthouse in Chicago to appeal the judge’s ruling.

Dunn argued that DeRogatis’ testimony would be irrelevant to the case.

But Gaughan said the state shield law, which protects journalists from being forced to identify confidential sources, does not apply in this instance, since he would not allow the defense to identify the source of the tape, how he got it, or whether he made a copy. Defense attorneys in a previous court session suggested that making a copy of the tape would itself be a criminal act covered by child pornography laws.

The defense, the judge said, had stated “seven times that they are not interested in his sources,” according to the account by the Sun-Times.