John Marion Grant was born on April 12, 1961, in Ada, Oklahoma. He was one of nine children in his family. Grant's father was not in the picture during his childhood. He and his siblings grew up in a very poor environment, living in a house with a dirt floor and no running water. Their mother struggled with alcoholism and was seen as neglectful and physically abusive. Because of this situation, Grant's six-year-old sister often took care of him.

As a child, Grant faced many challenges. To help feed his siblings, he began stealing at a young age. His life took a different turn when he was first imprisoned in the 1970s at the age of 11 or 12. By the time he was 15, he had lost all contact with his family. His legal representatives claimed that Oklahoma's juvenile justice system was among the worst in the country during that time. Reports revealed that many young people faced abuse while in the juvenile justice system.

On November 13, 1998, John Grant was involved in a violent incident at the Dick Conner Correctional Center in Oklahoma. Grant had been in prison since December 30, 1980, serving a sentence for armed robbery. On the morning of the murder, Grant and Gay Carter, a prison cafeteria worker, argued over his breakfast tray. Inmates who witnessed the argument later reported that Grant threatened Carter during this exchange.

After the argument, Grant was seen lingering near a storage closet that contained cleaning supplies. When Carter walked by, Grant grabbed her and pulled her into the closet. Inside the closet, Grant used a prison-made shank to stab Carter multiple times. He stabbed her in the chest, inflicting sixteen wounds, one of which fatally punctured her aorta.

When a correctional officer arrived, Grant fled the scene and attempted to take his own life with the same weapon. However, prison staff quickly subdued him. Despite medical efforts, Carter was pronounced dead later that day due to the serious injuries she sustained.

In May 2000, Grant was convicted of Carter's murder and sentenced to death. After years of legal appeals, Grant's execution was scheduled. On October 28, 2021, he was executed by lethal injection in Oklahoma. The execution was marked by significant controversy due to Grant's reaction to the drugs administered. Eyewitnesses reported that he began to convulse and vomit during the process.

The first drug administered was midazolam. After this, Grant showed physical signs of distress, including vomiting and convulsing. Despite witness accounts of severe reactions, Oklahoma officials later disputed these claims, stating that there were no unusual behaviors noted except for some regurgitation.

John Grant was pronounced dead 21 minutes after the execution process began. His death resulted in scrutiny regarding the state's execution methods and the reactions of the drugs used in lethal injections. An autopsy later revealed that Grant inhaled vomit and suffered from fluid buildup in his lungs, suggesting he experienced a sensation similar to suffocation before he died.