John Arthur Spenkelink was born on March 29, 1949, and raised in California. His early life was marked by tragedy and instability. At just 12 years old, he discovered his father’s body inside a truck, the result of suicide by carbon monoxide poisoning. His father was described as an alcoholic and a farmer, and the trauma of this discovery may have had a lasting effect on Spenkelink.

Throughout his teenage years, Spenkelink was frequently in trouble with the law. He faced multiple arrests and spent time in reform schools and jails. Despite these setbacks, he got married at the age of 18, although the relationship appears to have been short-lived and not well documented.

By the early 1970s, he had been convicted in California for armed robbery. His crimes included the robbery of a fast food restaurant, several gas stations, and individual victims. He was sentenced to a term of five years to life but managed to escape from custody in 1972.

On February 4, 1973, Spenkelink, then 24 years old, was traveling with a man named Joseph J. Szymankiewicz, whom he had picked up while hitchhiking. The two men checked into a hotel in Tallahassee, Florida. They were reportedly involved in a robbery spree, although details surrounding their partnership remain murky. According to Spenkelink, a heated argument escalated when Szymankiewicz allegedly stole from him, forced him to play Russian roulette, and sexually assaulted him. Spenkelink claimed he acted in self-defense when he shot Szymankiewicz in the back and struck him repeatedly with a hatchet.

Despite his version of events, Spenkelink was arrested less than a week later on February 9, 1973, in California on unrelated robbery charges. The murder weapon was later recovered from the apartment of an associate. He was extradited to Florida, where he was charged with first-degree murder. Spenkelink rejected a plea deal for second-degree murder, which would have spared him the death penalty and resulted in life imprisonment.

In court, his co-defendant, Frank Brumm, was acquitted but later claimed both he and Spenkelink had participated in the killing. Brumm told authorities that Spenkelink had offered him money to "get rid of" someone and that they drank a bottle of gin together over the corpse. Despite this statement, only Spenkelink was convicted.

He was sentenced to death in 1973, just one year after the U.S. Supreme Court had struck down the death penalty in Furman v. Georgia. After states, including Florida, rewrote their death penalty statutes, Spenkelink became one of the first individuals sentenced under the new laws.

By 1979, after exhausting appeals and despite public protest, Spenkelink became the first person executed in Florida after the death penalty was reinstated and the second in the entire U.S., following the voluntary execution of Gary Gilmore. Unlike Gilmore, Spenkelink did not consent to his execution, making him the first person involuntarily executed in the modern era.

His case attracted national attention. Celebrities, politicians, and activists, including actor Alan Alda and singer Joan Baez, rallied against his execution, claiming that capital punishment unfairly targeted the poor. Spenkelink himself was vocal in his opposition to the death penalty, often ending his prison letters with the phrase, “Capital punishment means those without capital get the punishment.”

On May 25, 1979, Spenkelink was electrocuted at Florida State Prison using the electric chair known as "Old Sparky." The execution was carried out amid a cloud of controversy. That same morning, a Florida radio DJ mockingly aired the sound of sizzling bacon and dedicated it to Spenkelink, highlighting the public divide over his fate.

Soon after, allegations emerged that Spenkelink may have been assaulted by prison guards prior to the execution. Witnesses reported the viewing windows had been obscured during the process, and Spenkelink’s family and clergy had been restricted from seeing him in his final hours. An investigation by the Florida governor found that while Spenkelink had been “taunted,” he had not been physically abused. However, the incident led to changes in the transparency of executions in the state.

Adding to the intrigue, a rumor surfaced suggesting Spenkelink may have been murdered before being brought to the execution chamber. His mother, disturbed by the speculation, had his body exhumed in 1981. A second autopsy, performed by Dr. Thomas Noguchi in Los Angeles, confirmed that the cause of death was indeed electrocution.