WASHINGTON, DC, United States (AP) – The US state of South Dakota on Monday executed an inmate who said that jurors at his trial were prejudiced against him because he was gay.

Charles Rhines, 63, was put to death by lethal injection soon after the Supreme Court rejected a last-ditch appeal by his lawyers claiming that his trial was tainted.

Rhines was sentenced to death in 1993 for killing an employee in a shop he was robbing in the rural state.

“It is very sad and profoundly unjust that the state of South Dakota today executed Charles Rhines, a gay man, without any court ever hearing the evidence of gay bias that infected the jury’s decision to sentence him to death,” his lawyer Shawn Nolan said.

According to a court filing on Rhines’ behalf, a juror who voted for the death penalty said that “we also knew that (Rhines) was a homosexual and thought that he shouldn’t be able to spend his life with men in prison”.

Another said that “there was lots of discussion of homosexuality” and “a lot of disgust”, according to the document.

“Anti-gay prejudice should never have any role in sentencing a man to death,” said Nolan.

Rhines’ case gained the backing of the powerful American Civil Liberties Union (ACLU), whose senior attorney Ria Tabacco Mar cited Supreme Court Chief Justice John Roberts as saying “our law punishes people for what they do, not who they are”

Last year, Rhines’ defence team appealed to the Supreme Court to take up the case and expand on a 2017 ruling that allowed it to examine secret jury deliberations in cases where there were strong grounds to suspect racial prejudice.

But the Supreme Court declined to do so, without giving a reason for the decision.

“Both racial prejudice and anti-gay prejudice have no place in the criminal justice system. Both undermine public confidence in the fairness of the system, particularly when jurors must decide between life imprisonment and death,” said Nolan.

The South Dakota attorney general’s office, however, said that the jury decided to impose the death penalty after hearing a recording of Rhines’ confession, and not because of his sexual orientation.

“The jurors have stated they were moved to a death sentence by the calloused and gruesome nature of the murder and, most of all, by Rhines’ bloodcurdling confession, in which he cackles while comparing (his victim’s) death spasms to a beheaded chicken running around a barnyard.”