Robert Alton Harris was born on January 15, 1953, in Fort Bragg, North Carolina. He was the fifth of nine children of Kenneth and Evelyn Harris. Kenneth Harris served in the United States Army and was awarded a Silver Star and a Purple Heart for his actions during World War II. Both of Robert's parents struggled with alcoholism. Robert was born two months premature and reportedly suffered from fetal alcohol syndrome. His father was known to be abusive, particularly toward Robert, whom he believed was conceived during an affair.

In 1962, after Kenneth was discharged from the Army, the Harris family moved to Visalia, California. In 1963, Kenneth was jailed for 18 months for sexually abusing his daughters. This led Robert's family to live a migrant lifestyle throughout the San Joaquin Valley. At the age of 13, Robert was detained in juvenile hall for stealing a car, and he spent four months there. During his time in detention, he faced sexual abuse.

When he was 14, his mother, Evelyn, abandoned the family in Sacramento. Left to fend for himself, he traveled to Oklahoma to stay with his siblings. However, he stole a car again, which resulted in his arrest in Florida. Robert spent three years in the Florida juvenile detention system until he turned 19, at which point he was released and moved to Chula Vista, California.

In June 1973, Robert married and had a son named Robert Jr., born in October 1974. His life continued to be troubled. In 1975, while living in a trailer park in Imperial County, he killed his brother’s roommate during a violent incident. He claimed it was to protect the victim's wife, but it was later revealed he had acted without provocation. He was convicted of voluntary manslaughter and sent to prison in San Luis Obispo. While in prison, his wife filed for divorce. Robert was eventually paroled in January 1978.

In July 1978, Robert Alton Harris and his brother Daniel planned to rob a bank. They stole two guns and traveled to San Diego. On July 5, they encountered two teenage boys, John Mayeski and Michael Baker, who were sitting in their car in a supermarket parking lot. The Harris brothers forced the boys into their vehicle and ordered Mayeski to drive to a quiet area at Miramar Lake.

Once at the lake, Robert Harris and Daniel ordered the boys to kneel on the ground. The boys began to pray. Robert then shot both of them multiple times. After the murders, the Harris brothers returned to Robert's home in Mira Mesa and allegedly ate the half-eaten cheeseburgers left by the victims.

About an hour later, they used the stolen car to rob a nearby bank, taking approximately $2,000. A witness from the robbery noted the car's details and reported it to the police. The Harris brothers were arrested less than an hour after the robbery took place.

Robert faced serious charges, including auto theft, kidnapping, and murder. While he pleaded guilty to bank robbery and received a 25-year sentence, he was later convicted of murder and given the death sentence in 1979. Daniel was sentenced to six years for his role in the crimes.

Harris's execution went through many legal challenges and appeals. After years of legal battles, he was ultimately executed by gas chamber on April 21, 1992, at San Quentin State Prison. This execution was notable as it was the first in California in 25 years. Before his death, Harris requested a final meal of KFC, pizza, jelly beans, and soda.

At his execution, his final words were recorded, and they referenced the inevitability of death. After the execution, he was declared dead seven minutes later.