The U.S. Supreme Court ruled Monday that laws imposing mandatory sentences of life in prison without the possibility of parole on juvenile offenders are unconstitutional.

Ignoring the factor of youth in imposing "that harshest prison sentence ... poses too great a risk of disproportionate punishment," Justice Elena Kagan wrote for the majority in the 5-4 decision.

The five justices based their ruling on the Eighth Amendment of the U.S. Constitution, which prohibits cruel and unusual punishment.

The high court reached its decision after considering the cases of Evan Miller and Kuntrell Jackson, who were sentenced to life without parole in Alabama and Arkansas, respectively.

Both boys were 14 at the time of sentencing.

Miller was convicted of capital murder in a case involving the death of a 52-year-old neighbor.

The neighbor, Miller and another adolescent were drinking and taking drugs together when the older man attacked Miller, spurring the intoxicated teens to beat the adult and set his home on fire.

Jackson was sentenced for an attempted robbery in which a store clerk was fatally shot, though Kuntrell was not the shooter.

Nationwide, upwards of 80 percent of the approximately 2,500 people serving life without parole for murders committed as minors are in that situation due to mandatory sentencing laws, according to data submitted to the Supreme Court. EFE