SPRINGFIELD — A man who was found guilty for acting as the lookout in a double homicide nearly three decades ago is asking the Illinois Supreme Court to find his mandatory life sentence without parole unconstitutional.A lawyer for Antonio House argued before the Supreme Court Tuesday that his life sentence for a crime committed when he was 19 violates the so-called proportionate penalties clause of the Illinois Constitution.This clause in the constitution states: “All penalties shall be determined both according to the …