A little more than two months after King's death, on June 8, 1968, Ray, an escaped convict who had broken out of the Missouri State Penitentiary a year before the assassination, was captured at London's Heathrow Airport while trying to leave the United Kingdom on a false Canadian passport in the name of Ramon George Sneyd. Ray was quickly extradited to Tennessee and charged with King's murder, confessing to the assassination on March 10, 1969, (though he recanted this confession three days later) and was sentenced to 99 years in prison. Ray, a presumed white supremacist and segregationist, had allegedly killed King because of the latter's extensive civil rights work. On the advice of his attorney Percy Foreman, Ray took a guilty plea to avoid a trial conviction and therefore the possibility of receiving the death penalty.

As it turned out, it is highly unlikely that a death sentence would have been carried out, as the US Supreme Court's 1972 decision in the case of Furman v. Georgia invalidated all state death penalty laws then in force.

Ray fired Foreman as his attorney (from then on derisively calling him "Percy Fourflusher") claiming that a man he met in Montreal, Canada using the alias "Raoul" had been deeply involved, as was his brother Johnny, but not himself, further asserting that although he didn't "personally shoot Dr. King," he may have been "partially responsible without knowing it," hinting at a conspiracy. He spent the remainder of his life attempting (unsuccessfully) to withdraw his guilty plea and secure the trial he never had.

Ray and six other convicts escaped from Brushy Mountain State Penitentiary in Petros, Tennessee on June 10, 1977 shortly after Ray testified that he did not shoot King to the House Select Committee on Assassinations, but were recaptured on June 13 and returned to prison. More years were then added to his sentence for attempting to escape from the penitentiary.

In 1997 Martin Luther King's son Dexter King met with Ray, and publicly supported Ray's efforts to obtain a retrial. Loyd Jowers was brought to a civil court and was prosecuted as being part of a conspiracy to murder Martin Luther King; Jowers was found guilty and the King family was awarded $100 in retribution as a sign that they were not following the case for monetary reasons. Some doubt the significance of the trial, especially considering that Jowers had previously confessed to an involvement in the murder, and therefore the trial was less of a case against Jowers than an effort to elaborate on his previous confession. Most historians disagree with the conclusion made by the jury.

Dr. William Pepper fought as James Earl Ray's lawyer up until Ray's death and then carried on, on behalf of the King family. The King family does not believe Ray had anything to do with the murder of Martin Luther King.

Ray died in prison on April 23, 1998 at age 70 from complications related to kidney disease, caused by hepatitis C probably contracted as a result of a blood transfusion given after a stabbing while at Brushy Mountain State Penitentiary. It was also confirmed in the autopsy that he died of liver failure.