An inmate who killed a prison guard during a botched jailbreak in 2007 was executed in Texas on Tuesday after waiving his right to appeal, prison authorities announced.
Jerry Martin, 43, was pronounced dead at 6:27 pm local time (0027 GMT) after being injected with a lethal dose of pentobarbital, an anesthetic commonly used to euthanize animals, the Texas Department of Justice said in a statement.
Martin was sentenced to death in 2009 after fatally wounding a prison employee trying to prevent his escape two years earlier.
Martin had been serving a 50-year sentence for attempted murder when he launched an escape bid with another prisoner in September 2007.
After stealing a city truck, he plowed into a horse ridden by mounted prison guard Susan Canfield, 59, who died on the spot after suffering serious head injuries.
Martin had initially sought to appeal, but abandoned his case in early 2013 following the death of his father, telling a trial judge that "for the first time in my life I felt what it was like to lose a loved one."
"I think Mrs Canfield's family deserves that closure," Martin said in statements to the court explaining his decision.
In his final words before execution, Martin again apologized to his victim's family.
"I would like to tell the Canfield family I'm sorry. Sorry for your loss. I wish I could take it back, but I can't," he said.
"I hope this gives you closure. I did not murder your loved one, it was an accident. I didn't mean for it to happen. I take full responsibility."
Tuesday's execution is the 36th carried out in the United States this year, and the 16th performed in Texas.
Texas uses a barbiturate procured from and prepared by a pharmacy, after the refusal of European suppliers to provide drugs for the purpose of executing human beings.