Whether the Eighth Amendment's Cruel and Unusual Punishments Clause requires proportionality review of a term-of-years or life prison sentence, rather than applying only to barbaric punishments or capital sentences.
Holding
Yes. The Eighth Amendment prohibits criminal sentences that are grossly disproportionate to the crime, including sentences of imprisonment, although successful noncapital proportionality challenges will be exceedingly rare.
Reasoning
The Court traced proportionality to English common law, Magna Carta, the English Bill of Rights, and the Eighth Amendment's adoption of the English Bill of Rights' language. That history supported the principle that punishment may not be excessive in relation to the offense, including punishment by imprisonment.
Prior decisions also recognized proportionality as an Eighth Amendment principle. Weems invalidated an excessive sentence for falsifying a public document; Robinson held that even a short prison term could be cruel and unusual when imposed for an impermissible offense; and the Court's capital cases had invalidated penalties excessive in relation to the defendant's conduct and culpability.
The Court rejected the claim that imprisonment is exempt from proportionality review. It would be anomalous for the Eighth Amendment to prohibit excessive fines and disproportionate death sentences, yet permit an excessive prison sentence without constitutional scrutiny. Still, legislatures retain broad authority to set punishment ranges and trial courts retain broad sentencing discretion, so reviewing courts should intervene only in exceptional cases.