Ronnie Lee Gardner was born on January 16, 1961, in Salt Lake City, Utah. He was the youngest of seven children born to parents Dan and Ruth Gardner. Dan Gardner struggled with alcohol addiction and left the family when Ronnie was just a toddler. He and Ruth divorced when Ronnie was 18 months old. Six months later, he was found malnourished and wandering the streets alone, wearing only a diaper. This incident led child welfare workers to take him into custody, but they later returned him to his mother.

Gardner had a difficult upbringing. He reported that he had a tumultuous relationship with his father, who often doubted if he was Ronnie's biological dad. Gardner claimed to have been raised by an older sister and experienced sexual abuse from some of his siblings. As a child, he and his sister Bonnie would sometimes run away from home to find shelter in a "hobo camp." By the age of ten, Gardner had developed a drug addiction and had access to alcohol. He and his brother Randy were arrested for stealing cowboy boots and sent to juvenile detention. Gardner was distressed when his father came to take Randy home but left him behind.

Ruth later married Bill Lucas, who had been in prison. The new family grew to include nine children. Gardner admired Lucas, who often engaged in illegal activities with his stepsons. By his early teen years, Gardner faced institutionalization and was placed in several detention centers, including an involuntary commitment at Utah State Hospital.

As a small child, Gardner had to fight to earn respect. He once described himself as "a nasty little bugger." While at the Utah State Industrial School, he met Jack Statt, who later became his foster parent. Gardner claimed that his time living with Statt was the most stable period of his life, despite the abusive environment. This period included sexual abuse, which Gardner considered normal at the time.

During his youth, Gardner met Debra Bischoff at an apartment complex where his mother lived. They began a relationship, and Gardner had a daughter in May 1977 and a son in February 1980 with her. However, during this time, he was also involved in criminal activities, leading to his conviction for robbery and imprisonment in the same month his son was born.

During the night of October 9, 1984, Ronnie Lee Gardner robbed the Cheers Tavern in Salt Lake City and shot bartender Melvyn John Otterstrom in the face, which resulted in Otterstrom's death. Gardner was arrested three weeks later at his cousin's home. He claimed Otterstrom put up a fight, but there was no evidence to support this. Gardner's bail was set at $1.5 million. His getaway driver, Darcy Perry McCoy, testified against him.

While on trial for the murder of Otterstrom on April 2, 1985, Gardner attempted to escape from custody at the Metropolitan Hall of Justice. He managed to smuggle a revolver into the courthouse. As he tried to shoot his way out, he was shot in the shoulder by a guard. He then shot unarmed bailiff George "Nick" Kirk in the abdomen and fatally shot attorney Michael Burdell in the eye. Gardner fled but was soon surrounded by police officers.

After this incident, Gardner was taken to a hospital where he recovered. Burdell died during surgery, while Kirk survived his injuries. The failed escape attempt led to investigations that found a bag of men's clothing in the courthouse and raised questions about security.

In June 1985, Gardner pleaded guilty to the murder of Otterstrom and received a sentence of life imprisonment without parole. He later faced charges for the murder of Burdell during his attempt to escape, and the jury found him guilty of capital murder in October 1985. Gardner was sentenced to death, choosing execution by firing squad over lethal injection.

Over the years, Gardner's time in prison included violent incidents. He stabbed another inmate in 1994 but was not charged with capital murder since the victim survived. In 1996, Gardner expressed a desire to be executed by firing squad, citing his background. He spent years in appeals, claiming brain damage and seeking commutation.

On June 15, 2010, Gardner was prepared for execution. He had his last meal and spent time with family. Gardner was executed by firing squad on June 18, 2010. The firing squad, made up of certified police officers, shot him while he sat restrained in a chair. Gardner was pronounced dead shortly after the execution began. He was the first person to be executed by firing squad in the United States since 1996. His body was cremated and returned to his family.