Former American Idol Judge Kara DioGuardi Sued Over Car Accident

The man doing the suing is Joel Postorino -- who claims he suffered a serious disc injury in his neck after a woman driving a 2005 BMW smashed into the back of his Porsche at an L.A. intersection last May.

In his lawsuit, filed in L.A. County Superior Court, Postorino claims the only person in the BMW during the crash was a woman named Christina Kline ... but Kara happens to be a registered co-owner of the BMW, so the man feels the former "Idol" star should have to pay up too.