The Supreme Court on Monday agreed to hear a case challenging a law in Kansas and four other states that abolishes a criminal defendant’s ability to plead insanity.

At the center of the dispute is a Kansas man named Kraig Kahler, who argues his depression was so severe and his mental state was so disturbed when he killed his estranged wife, two of his three kids and his mother-in-law in 2009 that he was unable to control his actions.