A man convicted of fatally stabbing his ex-girlfriend, her young son and her mother 13 years ago has been executed by Texas prison officials.
The lethal injection of Jose Villegas, 39, was carried out after his lawyers unsuccessfully argued to the US Supreme Court that he was mentally impaired and ineligible for the death penalty.
Villegas was pronounced dead 11 minutes after being given a lethal dose of pentobarbital. He became the seventh prisoner executed this year in America's most active death penalty state.
As the dose of pentobarbital began taking effect, he said, "It does kind of burn. Goodbye." He gasped several times, then began breathing quietly. Within less than a minute, all movement had stopped.
His lawyers filed a last-day appeal asking the Supreme Court to stop his punishment, saying testing in February showed he had an IQ of 59. The high court denied it several hours later.
The Supreme Court has prohibited execution of mentally impaired people, although states have been allowed to devise procedures to make their own determinations. Courts have also embraced scientific studies that consider a 70 IQ a threshold for impairment, and the high court justices are reviewing a Florida law stipulating that number for death penalty eligibility.
The Texas Attorney General's office disputed the IQ finding, saying previous examinations of Villegas showed no mental impairment and the number cited in his appeal was based on testing after he received an execution date and had no incentive to do well on the test.
Villegas was convicted of stabbing Erida Salazar, 23, her three -year-old son Jacob, and Ms Salazar's mother, Alma Perez, 51, in Corpus Christi in January 2001. Their bodies were discovered by Ms Salazar's father when he returned home after being excused from jury duty. Each had been stabbed at least 19 times.
Villegas, a former cook, dishwasher and labourer, was free on bond for a sexual assault charge and was supposed to go on trial on the day of the killings for an incident in which a woman said he punched her in the face.
Police spotted Villegas driving Ms Salazar's stolen car and he led them on a chase that ended with him on foot and urging officers to shoot him. When arresting him, police found three bags of cocaine in his baseball cap.
Following his conviction for capital murder, Villegas was convicted of two counts of indecency with a child related to the daughter of the woman he was accused of punching in the face prior to the killings.
Villegas also had convictions for making terrorist threats to kill women, burglary and possessing inhalants.
Lawyers argued the killings were not intentional and Villegas was mentally ill. A defence psychiatrist said Villegas experienced "intermittent explosive disorder", a condition that led to uncontrollable rages.
Villegas became the third Texas inmate executed with a new stock of pentobarbital from a provider corrections officials have refused to identify, citing the possibility of threats of violence against the supplier. The Supreme Court has upheld that stance.