Until recently, the U.S. was the only developed country in the world in which people under 18 could be sentenced to death or to a mandatory sentence of life without parole. For almost a decade, the Supreme Court has chiseled away at laws allowing these sentences. In 2005, the court ruled that juveniles’ "lack of maturity," susceptibility "to negative influences and outside pressures," and "transitory, less fixed" personality traits meant they couldn't be sentenced to death. Following this logic, it ruled five years later that juveniles couldn't be sentenced to life without parole for non-homicide offenses.
Then, in 2012, in Miller v. Alabama, the court ruled that a mandatory sentence of life without parole, handed down in 29 states’ murder cases as well as those in federal court, is unconstitutional for offenders younger than 18.
The decision left a question on the table: What about those who had already been convicted? Should they be resentenced?