Tennessee has executed its longest-serving death row inmate, who became the second person put to death in the state’s electric chair in just over a month.

Corrections officials said 61-year-old David Earl Miller was pronounced dead at 7.25pm on Thursday at a Nashville maximum-security prison.

Both Miller and Edmund Zagorski before him chose the electric chair over lethal injection, a process proponents said would be painless and humane.

But the inmates argued in court that Tennessee’s current midazolam-based method causes a prolonged and torturous death.

Execution-TennesseeProtesters against the death penalty outside Riverbend Maximum Security Institution in Tennessee (Shelley Mays/The Tennessean via AP)

They pointed to the August execution of Billy Ray Irick, which took around 20 minutes and during which he coughed and huffed before turning a dark purple.

Their case was thrown out, largely because a judge said they failed to prove a more humane alternative was available.

Zagorski was executed on November 1.

Governor Bill Haslam declined on Thursday to intervene in Miller’s planned execution.

In recent decades, states have moved away from the electric chair, and no state now uses electrocution as its main execution method, said Robert Dunham, executive director of the Death Penalty Information Centre, which does not take a stand on the death penalty but is critical of its application.

Georgia and Nebraska courts both have ruled the electric chair unconstitutional, and about two decades ago it looked as though the US Supreme Court would weigh in on the issue.

It agreed to hear a case out of Florida after a series of botched executions there. But Florida adopted lethal injection, and the case was dropped.

Mr Dunham said he was not aware of any state other than Tennessee where inmates were choosing electrocution over lethal injection.

In Tennessee, inmates whose crimes were committed before 1999 can chose electrocution over lethal injection.

Execution-TennesseeProtesters against the death penalty gather for song and prayer outside Riverbend Maximum Security Institution (Shelley Mays/The Tennessean via AP)

Zagorski’s execution was delayed about three weeks after he requested the electric chair amid a last-minute flurry of legal manoeuvres.

The state initially refused his request until a federal court judge ordered the state to comply.

Mr Haslam ordered a brief reprieve to “give all involved the time necessary to carry out the sentence in an orderly and careful manner”.

The builder of Tennessee’s electric chair warned that it could malfunction, but Zagorski’s execution appeared to be carried out without incident. It was only the second time Tennessee had put an inmate to death in the electric chair since 1960.

The courts said Miller could not challenge the constitutionality of the electric chair because he chose it, even though his attorneys argued the choice was coerced by the threat of something even worse.

Miller was convicted of killing 23-year-old Lee Standifer in 1981 in Knoxville.

Standifer was a mentally handicapped woman who had been on a date with Miller the night she was repeatedly beaten, stabbed and dragged into some woods.

Miller spent 36 years on Tennessee’s death row, the longest of any inmate.