DETROIT (AP) — The Michigan Supreme Court has heard arguments that could wipe out charges against former Gov. Rick Snyder and eight others in the Flint water scandal.

Defense lawyers are challenging a rarely used method to investigate crimes and file indictments.

Snyder and others were indicted by a judge who served as a one-person grand jury in Genesee County. Evidence was offered in private by the attorney general’s office.

People charged with felonies in Michigan typically have a right to a hearing where they can argue there’s not enough evidence to send a case to trial. But the one-person grand jury process doesn’t allow it.

Defense lawyers claim it’s unconstitutional.

Prosecutors say they’re simply following a method approved by the Legislature.