A jury found Earl Ellis Green, 46, guilty on May 11 of shooting Officer Ryan Bonaminio, 27, in 2010 after a traffic stop.
Prosecutors say Green ambushed the officer, beat him with a steel pipe, took his service weapon and then shot him in the head.
Jurors must decide between a death sentence or life in prison.
During the penalty phase, the Riverside County District Attorney's Office introduced jurors to Green's life as a career criminal, which dates back to 1990 when he was convicted of assaulting a Banning police officer. The prosecution also laid out an incident in 1993 when Green was convicted of evading police and attempting to fight his way out of an arrest after a foot chase. It took three Riverside police officers to subdue him.
During the defense's opening statements, jurors were asked not to excuse Green's past actions, but to consider the reason behind them. Jurors learned about Green growing up in an abusive home from which he ran away repeatedly before going into the foster system.
Jurors were also told about his life in and out of the juvenile system in which a psychiatrist noted "he possesses very few skills dealing with his anger and feelings." The defense blamed the system for failing to treat and correct Green's mental issues.