Bigler Stouffer spent more than 35 years on death row for the 1985 murder of schoolteacher Linda Reaves and the attempted murder of her boyfriend, Doug Ivens.

The 79-year-old Stouffer was executed at the Oklahoma State Penitentiary in McAlester after the Supreme Court and governor Kevin Stitt denied last-minute requests to halt the execution.

An Oklahoma Department of Corrections spokesman said the execution using a cocktail of lethal drugs was carried out with “no complications”.

Stouffer was the second person executed in Oklahoma this year.

John Grant, 60, also a convicted murderer, vomited and experienced convulsions as he was put to death by lethal injection in October, according to witnesses.

Grant was the first inmate to be put to death in Oklahoma since 2015, when a series of botched executions led to a temporary moratorium on capital punishment in the state.

The US Supreme Court struck down the death penalty in 1972 but reinstated capital punishment four years later.

The number of executions carried out annually in the US has been declining in recent years.

Capital punishment has been abolished in 23 US states, while three others – California, Oregon and Pennsylvania – have observed a moratorium on its use.

There have been three federal executions in the US this year and eight state executions: three in Texas, two in Oklahoma and one each in Alabama, Mississippi and Missouri.

There are no further executions scheduled this year, according to the Death Penalty Information Center.

There were 17 executions in the US in 2020, when a number of states suspended capital punishment because of the Covid-19 pandemic.

Then-president Donald Trump resumed federal executions after a 17-year hiatus, however, and 10 federal inmates were put to death in 2020.

President Joe Biden halted federal executions after taking office in January.