The first prisoner to be executed in South Carolina in more than 10 years has chosen to die by firing squad rather than in the electric chair.

Richard Bernard Moore, 57, is also the first inmate in the US state to select his execution method after a law was enacted last year making electrocution the default, with an option to face three prison workers with rifles instead.

He has spent more than 20 years on death row for the 1999 killing of a convenience store clerk named James Mahoney in Spartanburg.

His execution is scheduled for 29 April.

If it goes ahead, he would be the first person put to death in the state since 2011.

The new law led to a decade-long break which corrections officials blamed on an inability to obtain the drugs needed to carry out lethal injections.

Moore’s lawyers have petitioned the state Supreme Court to delay his death while another court decides if either of the two available methods constitutes cruel and unusual punishment.

They say prisons officials are not working hard enough to get the lethal injection drugs, forcing prisoners to choose between two more barbaric methods.

Moore’s lawyers are also asking the state Supreme Court for a delay to allow the US Supreme Court to review whether his death sentence is too severe a punishment when compared with similar crimes.

The state justices rejected a similar appeal last week.

The state corrections agency completed developing procedures for firing squad executions last month and spent $53,600 (£41,025) to renovate the death chamber in Columbia, which included installing a metal chair with restraints that faces a wall with a rectangular opening 15 ft (4.6m) away.

Dying by firing squad would involve three volunteer prison workers using their rifles to shoot the condemned prisoner’s heart.

South Carolina is among four states that allow a firing squad, according to the Washington-based nonprofit Death Penalty Information Center.

It is one of eight states that still use the electric chair.