HARRISBURG -- Twenty-one counties that have at least one state prison each want the Department of Corrections to pay for prosecuting inmates when crimes are committed inside the institutions.

The counties argue that a 4-year-old change to state law requires the state to pick up the tab for court personnel, witness fees, court-appointed lawyers and other expenses whenever a crime occurs inside a state prison.

A spokeswoman for the prison system, however, said its lawyers interpret the law differently.

Prior to 2000, when a state inmate committed a crime, the county in which the prison is located could bill the county that sentenced the inmate for prosecution costs.

Montgomery County, home to Graterford State Prison, tried to bill the state for 21 criminal matters but was denied payment, according to an 11-page lawsuit dated Monday.

The counties want a Commonwealth Court judge to interpret the statute and issue a declaratory judgment.

The Commonwealth Court filing office had no record of the lawsuit yesterday afternoon.