It was a 5–4 decision in which the United States Supreme Court applied its capital proportionality principle, to set aside the death penalty for the driver of a getaway car, in a robbery-murder of an elderly Floridian couple.

While Earl Enmund sat outside in the getaway car, his accomplices Sampson and Jeanette Armstrong rang the doorbell of Thomas and Eunice Kersey, who lived at a farmhouse in Central Florida.

At a separate penalty hearing, the trial judge found that the murders were committed for pecuniary gain and were especially heinous, atrocious, or cruel, and no statutory mitigating factors applied, and then sentenced Enmund to death.

It held that the "felony murder rule and the law of principals combine to make a felon generally responsible for the lethal acts of his co-felon.

"[1] Justice Brennan delivered a concurring opinion and stated that the death penalty is a cruel and unusual punishment prohibited by the Eighth Amendment in all circumstances.