Convicted killer Marvin Wilson is looking to the U.S. Supreme Court to keep him from the Texas death chamber.  Attorneys for the 54-year-old Wilson say he's mentally impaired and should be spared from lethal injection in Huntsville this evening. The high court has barred execution of mentally impaired people.  Texas State lawyers contend the single test that indicated mental impairment was faulty and the results are different in all other psychological testing of the Jefferson County man.  Wilson is set for execution later this evening for the abduction and fatal shooting of 21-year-old Jerry Williams, unless he determined to mentally impaired.