Roper v. Simmons
Simmons appealed his conviction.  Each appeals court which heard his case agreed with the original jury's death sentence.  Then the United States Supreme Court decided in Atkins v. Virginia 536 U.S. 304 (2002) that executing people with intellectual disabilities was unconstitutional.  Encouraged, Simmons filed a new petition to the Supreme Court of Missouri.  That court decided that "a national consensus has developed against the execution of juvenile offenders," meaning that across the country, most Americans disagreed with executing juveniles.  The court ruled that executing juveniles is cruel and unusual punishment, which violates the Eighth Amendment to the United States Constitution.  They changed Simmons' sentence from death to life in prison.