Richard Masterson, 43, admitted that he strangled Darin Honeycutt, a transvestite, in 2001 in Houston. However, Masterson says that the victim died of a heart attack during consensual sexual relations.
Honeycutt asked to be choked to reach a state of erotic asphyxiation, a practice that deprives the brain of oxygen to reach a more intense orgasm.
On Friday, the Texas Board of Pardons and Paroles refused a request for a stay of execution.
Masterson, who is scheduled to be executed by lethal injection, would be the second person executed in the United States in 2016.
On Tuesday, his attorney filed a motion of stay of execution to the US Supreme Court, claiming that Honeycutt “died of a heart attack, making his death accidental and not a homicide at all.”
In the petition, the lawyers say that Masterson’s case “presents a perfect storm of attorney incompetence and neglect combined with a severely mentally ill, suicidal defendant who did not kill anyone.”
Since Masterson was convicted of murder, new information has surfaced, including that “the state’s medical examiner was a fraud who was unqualified to opine on the decedent’s cause of death,” says the petition.
“After consulting qualified medical experts, Mr. Masterson learned that the decedent did not die from strangulation… he died from a heart attack caused by a pre-existing heart condition.”
Pope Francis, a death penalty opponent, is closely following the case, said Austrian Cardinal Christoph Schonborn at a press conference Monday.
Another Catholic anti death-penalty activist, Sister Helen Prejean, wrote on Twitter that she has “serious doubts about Richard’s guilt.”
The grounds for filing the Supreme Court petition are that Masterson “is actually innocent, the state suppressed evidence of Mr. Masterson’s innocence, and Mr. Masterson’s prior lawyers were incompetent when they did not notice the evidence of his innocence,” Masterson’s attorney Gregory Gardner told AFP.
Pope Francis reaffirmed his opposition to the death penalty in September when he spoke to Congress on a visit to the United States.
Twenty-eight people were executed in the United States in 2015, according to the non-profit Death Penalty Information Center.