AUSTIN, Texas (Reuters) – Texas prepared to execute on Thursday a man convicted of murdering a woman in her San Antonio home in 2004 as his lawyers made a last-minute appeal to the U.S. Supreme Court to spare his life.

TaiChin Preyor, 46, is to be executed by lethal injection at the state’s death chamber in Huntsville at 6 p.m. local time (2300 GMT). If the execution goes ahead, it would be the 543rd in Texas since the U.S. Supreme Court reinstated the death penalty in 1976, the most of any state.

Lawyers for Preyor launched the appeal on Thursday, arguing that prior counsel was incompetent and included a lawyer who lost his license two decades earlier and another attorney with no death penalty experience who used Wikipedia to navigate Texas’ death penalty system.

“His trial counsel ignored glaring references to significant mitigation evidence, depriving jurors of crucial information likely to persuade them to impose a life sentence,” Preyor’s lawyers said in their filing.

They have said that some of the mitigating evidence included a traumatic childhood, marked by severe physical and sexual abuse.

Preyor was convicted of killing Jami Tackett, 24. He also stabbed a man who was with her, who survived.

A U.S. district judge in San Antonio dismissed a motion from Preyor to halt the execution earlier this week.