Gargiulo is charged with the murders of Ashley Ellerin and Maria Bruno, and the attempted murder of Michelle Murphy in the Los Angeles area. Ellerin was set to go to out with actor Ashton Kutcher on the night of her murder in 2001.
The attacks all came between 2001 and 2008.
The locations include an apartment complex in El Monte.
Gargiulo faces the death penalty if convicted of all the charges.