PHILADELPHIA -- The mother of jailed rapper Meek Mill is calling on Philadelphia's district attorney to "step in" and help her son.

The reports the plea by Kathy Williams came during a brief news conference Tuesday before the start of a criminal justice panel at the University of Pennsylvania.

Williams strongly criticized the judge who sentenced Mill to two to four years in prison last fall for violating probation on a roughly decade-old gun and drug case. An appeals court in December denied a request to free the 30-year-old musician on bail.

Representatives of Mill previously have asked that the district attorney's office intervene in the case.

A spokesman for District Attorney Larry Krasner declined to comment on the request.