WASHINGTON — The Supreme Court is adding a new case to decide whether its 3-year-old ruling throwing out mandatory life in prison without parole for juveniles should apply to older cases.

The court was scheduled to hear arguments in a case from Louisiana in late March, but the state released inmate George Toca after 30 years in prison.

The justices on Monday said they would consider a new Louisiana case involving a man who has been held since 1963 for killing a sheriff’s deputy in Baton Rouge.

Henry Montgomery was a 17-year-old 10th-grader who was playing hooky from school when he shot Deputy Charles Hurt at a park near the city’s airport. The officer and his partner were looking to round up truants.

The case will be argued in the fall.

In 2012, the justices ruled that judges and juries must take account of age when sentencing people who were younger than 18 at the time of even the most brutal crimes.

Courts around the country have differed on whether prison inmates whose cases are closed can take advantage of the high court ruling and seek parole or new sentencing hearings.

The Supreme Court has handed down a series of rulings that hold juveniles less responsible than adults when their sentences are considered. The latest case involves how the court’s views about juvenile sentences mesh with another line of cases that deal with when major court decisions should apply retroactively to older cases.

The case is Montgomery v. Louisiana, 14-280.