WASHINGTON — The Supreme Court on Monday agreed to decide whether juveniles convicted of killing someone may be locked up for life with no chance of parole, a follow-up to last year’s ruling barring such sentences for teenagers whose crimes do not include killing.

The justices will examine a pair of cases from the South involving young killers who are serving life sentences for crimes they committed when they were 14.

Both cases were brought by the Equal Justice Initiative in Montgomery, Ala. The institute said that life without parole for children so young “is cruel and unusual” and violates the Constitution.

The group says roughly six dozen people in 18 states are under life sentences and ineligible for parole for crimes they committed at 13 or 14.