On November 21, 1973, Troy Gregg and Floyd Allen were hitchhiking north in Florida when they were picked up by Fred Simmons and Bob Moore in their car.
Their car broke down. Simmons purchased another vehicle with some of the cash he was carrying. While still in Florida, the group picked up Dennis Weaver, who rode with them to Atlanta, where he was let out about 11 p.m.
A short time later the four men stopped for a rest along the highway in Gwinnett County, Georgia. The next morning the bodies of Simmons and Moore were discovered in a nearby ditch.
On November 23, after reading about the shootings in an Atlanta newspaper, Weaver communicated with the Gwinnett County police and related information concerning the journey with the victims, including a description of the car. The next afternoon, Gregg and Allen, while in Simmons' car, were arrested in Asheville, North Carolina. In the search incident to the arrest a .25-caliber pistol, later shown to be that used to kill Simmons and Moore, was found in Gregg's pocket. After receiving Miranda warnings and signing a written waiver, Gregg signed a statement admitting he shot Simmons and Moore but claiming self-defense.
At the guilt stage of the bifurcated trial, a medical examiner testified that Simmons died from a bullet wound in the eye and that Moore died from bullet wounds in the cheek and in the back of the head. The examiner further testified that both men had several bruises and abrasions about the face and head. Gregg testified claiming self-defense after Simmons and Moore allegedly attacked with a pipe and knife, but the jury convicted him of two counts of armed robbery and two counts of murder.
At the penalty stage before the same jury, neither side presented additional evidence. The trial judge instructed the jury that it could recommend either a death sentence or a life prison sentence on each count. The judge further charged the jury that in determining the sentence it was free to consider mitigating or aggravating circumstances. The judge instructed that death could not be imposed unless the jury found beyond a reasonable doubt one of the aggravating circumstances. The jury found the first and second aggravating circumstances and returned verdicts of death on each count. The Supreme Court of Georgia affirmed the convictions and the death sentences for murder after reviewing the record and comparing the sentences to similar cases, but it vacated the death sentences for armed robbery. The United States Supreme Court granted certiorari limited to the challenge to the death sentences under the Eighth and Fourteenth Amendments.