Michael Dewayne Smith was born in Oklahoma, U.S., on June 24, 1982. He grew up in a neighborhood that was known for crime, gang violence, and drug activities. His early life was difficult. Smith's father was an alcoholic who abused his mother. By the time Michael was two years old, his parents separated. This separation affected him deeply.

Due to his challenging home situation, Smith began to abuse drugs at a young age. He was also influenced by his brothers, who introduced him to gangs. Smith struggled with school and did not perform well academically. During his childhood, he faced more trauma when he was sexually abused by an older woman around the age of seven or eight.

By the year 2000, Smith had joined a local street gang known as the Oak Grove Posse in Oklahoma City. His involvement in gang life led him further down a troubled path. By 2002, Smith was already wanted by the police for multiple serious crimes. His record included charges for shooting with intent to kill, assault, and driving under the influence.

On November 24, 2001, Michael Dewayne Smith and his accomplice David Walter Burns were involved in a shooting outside a nightclub in northeast Oklahoma City. They were inside a sport utility vehicle with two other men, Meldon Moore and Otis Payne Jr., when a fight broke out. During the altercation, both Smith and Burns fired their weapons. Otis Payne, aged 26, was killed, although the fatal shot was intended for Meldon Moore, who survived.

After this incident, Smith fled and became wanted by the police. While still on the run, he committed two additional murders on February 22, 2002, also in Oklahoma City. Early that morning, Smith went to the home of 41-year-old Janet Moore, looking for her son, whom he believed was a police informant. When he found Janet alone, he forced his way into her apartment and shot her.

Later that same day, Smith targeted 22-year-old Sarath Pulluru, a convenience store clerk. Believing that Pulluru had disrespected a deceased gang member, Smith held him at gunpoint and shot him multiple times before attempting to destroy evidence by setting fire to the store.

Smith was arrested two days after the murders of Moore and Pulluru, on February 24, 2002, in connection to the earlier murder of Otis Payne. He was charged with multiple offenses, including first-degree murder.

In June 2003, Smith stood trial for the murders of Moore and Pulluru. The trial ended in a mistrial due to procedural errors, but a second trial began in August. During this trial, witnesses testified about Smith's confession, and he was found guilty of both murders. On September 20, 2003, the jury recommended the death penalty for Smith.

In March 2004, he faced a second trial for the murder of Otis Payne and was sentenced to life imprisonment. His sentences for the murders of Moore and Pulluru were set to death, while the life sentence for Payne's murder was set to run consecutively.

Smith spent 21 years on death row, making several unsuccessful appeals. He maintained his innocence, claiming that his confession was coerced. In 2024, a clemency hearing was held, but the parole board denied his request for mercy. Smith was scheduled for execution on April 4, 2024. On that day, he was executed by lethal injection after his final appeals were rejected. He was pronounced dead at 10:20 AM.