Attorneys for a Corpus Christi man convicted of killing his ex-girlfriend, her 3-year-old son and her mother are trying to keep him from execution this week.

Jose Villegas is set to die Wednesday evening in Huntsville for the three slayings in January 2001. His lawyers say they've found new evidence that he's mentally impaired and ineligible for execution and need more time to investigate.

The Texas Court of Criminal Appeals on Monday refused to stop the punishment and his attorneys have said they'll appeal to the U.S. Supreme Court.

Villegas' former girlfriend, 23-year-old Erida Salazar, her son, Jacob, and her mother, 51-year-old Alma Perez, were stabbed repeatedly at the Perez home in Corpus Christi.

At the time, Villegas was out on bond on a sexual assault charge.