Chicago (AFP) - The US state of Texas executed an inmate Tuesday for the brutal killing of his girlfriend while he was on parole for the murder of his wife.

William Rayford lost his final appeals just hours prior to his evening execution, including at the US Supreme Court. The appeals delayed the process for a few hours, but the lethal injection was ultimately carried out and Rayford pronounced dead at 8:48 pm (0248 GMT).

The 64-year-old was convicted of killing his girlfriend Carol Lynn Thomas Hall in 1999, after an argument the two had in her home. At the time, Rayford was on parole, having served eight years of a 23-year sentence for the 1986 murder of his estranged wife Gail Ann Rayford.

His last statement included a request for forgiveness from the family of his second victim, according to the Texas Department of Criminal Justice.

"Please find it in your hearts to forgive me," Rayford said. "By no means am I happy for what I've done. I have asked the Lord to forgive me."

Both of Rayford's murders were brutal attacks that occurred in front of the women's children. Hall's body was found beaten, strangled and stabbed.

Hall's then 11-year-old son was also beaten and stabbed when he tried to stop the attack. He survived and was a witness in Rayford's trial.

Rayford's attorneys had asked the US Supreme Court to halt the execution, alleging the convict, who was black, had insufficient representation and that his initial sentencing may have been marred by race-based prejudice.

In another appeal, they claimed recent tests showed Rayford suffered decades-long brain damage caused by lead poisoning from bullets and bullet fragments lodged in his body, and from contaminated water.

None of the appeals panned out, as judges rejected them all.

The number of executions in the US declined to a near-historic low of 23 last year, according to the Death Penalty Information Center.