A Philadelphia judge’s decision last month to appoint a special prosecutor to pursue a violation of probation hearing was an unusual move, according to several attorneys, and may not pass constitutional muster.

According to court documents, in mid-September, Philadelphia Court of Common Pleas Judge Anne Marie Coyle appointed a special prosecutor in the case Commonwealth v. Mayfield. The defendant, Demetrius Mayfield, had previously been convicted on a gun charge and was out on probation when he was arrested in early September on new charges related to alleged gun and drug possession.