Roper v. Simmons
The Simmons case started in Missouri in 1993.  Christopher Simmons, who was 17, made a plan to murder a woman named Shirley Crook.  He brought two younger friends, Charles Benjamin and John Tessmer, into the plan. They planned to break into Crook's house, steal things, tie Crook up, and throw her off a bridge.  Tessmer dropped out of the plan at the last minute.  However, Simmons and Benjamin broke into Crook's home, drove her to a state park, and threw her off a bridge.