Update: A correction was made to clarify that Daniel T. Mallon, an assistant state appellate defender, argued on behalf of the defendant.SPRINGFIELD — A challenge from the state of Illinois to an intellectually disabled man’s vacated de facto life sentence seemed to fall short at the Illinois Supreme Court on Tuesday, even with some of the justices voicing hesitation about creating broad sentencing standards for a narrow class of defendants.The case concerns William Coty, 56, who in 2006 received a mandatory …