Image copyright Georgia Department of Corrections Image caption Ledford stabbed his 73-year-old neighbour to death in January 1992

A grinning death row inmate in the US state of Georgia used his final words at his execution to insult the witnesses.

JW Ledford Jr's lawyers argued death by firing squad would be more humane as lethal injection would be too painful.

But witnesses said the 45-year-old - who was served a 5,000-calorie last meal - showed no obvious discomfort as he was put to death early on Wednesday.

He was convicted of knifing his 73-year-old neighbour to death in 1992.

His victim was the physician who delivered Ledford at birth.

In Georgia's first execution this year, Ledford was pronounced dead at 01:17 after an injection of compounded barbiturate pentobarbital.

Witnesses said the prisoner grinned as they entered the viewing area of the death chamber at the state prison in Jackson.

Image copyright Warner Bros Image caption Paul Newman starred as a stubborn prisoner in Cool Hand Luke

Asked if he wished to make a final statement, Ledford appeared to quote from the 1967 film Cool Hand Luke, starring Paul Newman.

"What we have here is a failure to communicate," he said, a phrase uttered by the warden in the classic prison drama. "Some men you just can't reach."

Ledford added: "I am not the failure. You are the failure to communicate."

Still smiling, the prisoner said: "You can kiss my white trash ass."

Ledford continued talking, but his microphone was cut off.

Witnesses said he shut his eyes, took several deep breaths and went still three minutes after the warden left the room.

For his final meal on Friday, Ledford requested filet mignon wrapped in bacon with pepper jack cheese, large french fries, 10 chicken tenders with sauce, fried pork chops and a blooming onion.

For dessert he had pecan pie, vanilla ice cream and sherbet, washed down with a Sprite, according to WGLC-TV, an Atlanta news station.

Should killers on death row get a last meal choice?

Ledford robbed and murdered his neighbour, Dr Harry Johnston, stabbing him in the neck at his home on 31 January 1992.

He then threatened the victim's wife before stealing money, four guns and vehicle from the house.

The parole board rejected a request for clemency on Monday after Ledford's lawyers said he had a rough childhood and suffered an intellectual disability.

His legal team had argued that a lethal injection would expose him to "unconstitutional pain" because he had been taking a drug for nerve pain which they said could alter his brain chemistry.

They had argued that firing squad would be less painful, but a federal appeals court rejected the bid.

Only three states allow for this option as an alternative to lethal injection - Mississippi, Oklahoma and Utah.

According to the Atlanta Journal-Constitution, Georgia executed nine men last year, more than any other US state.

US death sentences fall to 40-year low