The life of a Missouri prison inmate hangs in the balance as the U.S. Supreme Court hears oral arguments in his death penalty case, but much more that his fate will be decided once the Court rules. The U.S. Supreme Court has taken up an appeal of the Missouri Supreme Court ruling that overturned Christopher Simmons’ death sentence. The state court ruled Simmons couldn’t be sentenced to death, because he was 17 at the time he killed Shirley Crook of Fenton. Simmons’ lawyer has argued that studies confirm a 17-year-old hasn’t matured enough to meet the constitutional threshold necessary to face death – an argument rejected by Attorney General Jay Nixon. The State Supreme Court ruled times have changed since the U.S. Supreme Court upheld juvenile executions in a 1989 ruling. Dick Kurtenbach with the American Civil Liberties Union in Kansas City says this is a big case for the state. The oral arguments will be heard Wednesday by the U.S. Supreme Court. A decision will come later.