Murderer Scott Panetti set to die by lethal injection on WednesdayCondemned must have rational understanding of why they are being killedAttorneys who contend that a condemned Texas inmate set to die this week is too delusional for execution asked the US supreme court on Monday to halt his lethal injection and determine whether mentally ill people should be exempt from the death penalty because it is unconstitutionally cruel punishment.Scott Panetti, 56, is set for lethal injection on Wednesday for the 1992 shooting deaths of his in-laws at their home in Fredericksburg in the Texas Hill Country.