A death row inmate due to be executed in days has asked to die by electric chair rather than face a controversial lethal injection.

Edmund Zagorski made the request hours before the Tennessee Supreme Court ruled the state’s three-drug injection protocol was legal, paving the way for his execution on Thursday.

Medical experts have said the method causes such severe pain it tortures inmates to death, while prisoners had argued in a lawsuit it should be banned under the US Constitution’s eighth amendment, which prohibits cruel and unusual punishment.

Kelley Henry, a public defender who led the case brought against the state by 32 inmates including Zagorski, said her client had now asked to die by electrocution.

“Faced with the choice of two unconstitutional methods of execution, Mr Zagorski has indicated that if his execution is to move forward, he believes that the electric chair is the lesser of two evils,” she said in an emailed statement.

“10-18 minutes of drowning, suffocation, and chemical burning is unspeakable.”

In Tennessee, death row inmates whose offences were committed before 1999 can opt to be executed either by lethal injection or electric chair.

Zogorski was sentenced in 1984 for the murder of two men during a drug deal the previous year.

Zagorski shot John Dotson and Jimmy Porter and their slit their throats after they tried to buy marijuana from him.

Alongside the request to die by electrocution, Ms Henry also said she would call for a stay of execution for her client so an appeal against the Supreme Court’s ruling could be lodged.

The majority opinion of the court found inmates failed to establish the three-drug protocol is unconstitutional because they did not prove there was a readily available alternative method that was more humane - a requirement of current federal and Tennessee law.

However, a number of medical experts testified claiming the cocktail of chemicals used in the injection leaves inmates feeling as if they are burning on the inside and being buried alive.

Ms Henry argued at a hearing last week a single dose of the barbiturate pentobarbital would be a more humane form of execution.

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Attorneys for the state said they have been unable to procure the drug, which became widely unavailable for executions after an uproar over its use for that purpose several years ago.

In August, Tennessee executed its first inmate in nearly a decade. The US Supreme Court declined to stay that execution and the state’s governor, Bill Haslam, has already said he will not intervene in Zagorski’s case.

Tennessee is one of only nine states that allow electrocutions, and just 14 of the 871 inmates executed in the United States since 2000 have been killed in the electric chair, according to the Death Penalty Information Centre.

The last electrocution in the US took place in Virginia in January 2013.