Ellerin was found dead in the house the next morning. She had more than 47 stab wounds.
Gargiulo is also accused of fatally stabbing 32-year-old Maria Bruno in her El Monte, California, apartment in 2005, and stabbing 26-year-old Michelle Murphy in her Santa Monica apartment in 2008. KTLA reported that Murphy survived and fought off Gargiulo, causing him to cut himself and leave a trail of blood, which led to his arrest.
He is expected to stand trial over the 1993 killing of Tricia Pacaccio, who was stabbed to death outside her family's Chicago home, according to E! News.
Before then, on Tuesday, he will move to the sanity phase of the trial to determine his state of mind during the California killings.