NASHVILLE, Tenn. (AP) — A Tennessee inmate is scheduled Thursday to become the fifth to die in the state's electric chair in the past 16 months. Each of those inmates chose electrocution over the state's preferred execution method — lethal injection.

Nicholas Sutton, 58, was sentenced to death in 1986 for killing fellow inmate Carl Estep in a conflict over a drug deal while both were incarcerated in an East Tennessee prison. Sutton had been serving time for three murders he committed in 1979 when he was 18, including that of his grandmother.

In a clemency petition to Gov. Bill Lee, Sutton's supporters said he is not the same man who went to prison forty years ago.

“I can confidently state that Nick Sutton is the most rehabilitated prisoner that I met working in maximum security prisons over the course of 30 years,” former Correction Lt. Tony Eden stated in an affidavit included with the clemency petition.

But Lee said Wednesday that he would not intervene in the execution. Two last-ditch appeals to the U.S. Supreme Court were still pending as of Wednesday night.

Sutton has not indicated why he chose electrocution — an option for inmates whose crimes were committed before the state adopted lethal injection as its preferred execution method — but other inmates have said they thought the electric chair would be quicker and less painful.

Expert witnesses testifying in 2018 on behalf of Tennessee inmates challenging the state's three-drug lethal injection protocol said the mix of drugs would cause sensations of drowning, suffocation and chemical burning while rendering them unable to move or call out.

Inmates' attorneys have argued without success that both lethal injection and electrocution violate the Constitution's ban on cruel and unusual punishment.

The electric chair fell out of favor in the 1990s following several gruesomely botched executions, including a Florida execution where smoke and flames shot from the head of the condemned inmate. Only one other state, Virginia, has used electrocution this decade, and it has not done so since 2013.