Earl Ellis Green is accused of shooting and killing 27-year-old Officer Ryan Bonaminio after ambushing him during a foot chase Nov. 7, 2010.
Green is charged with one count of murder, along with two special circumstances. Prosecutors said they will seek the death penalty.
During opening statements, the district attorney said Stephen McQueen, a homeless man at the time of the crime, witnessed the murder take place.
McQueen and his girlfriend were at the Riverside Community Center for Spiritual Living that night. McQueen says it was just before 10 p.m. when he saw a police officer chasing an unidentified man up a slope, then across the parking lot toward a staircase.
That's when McQueen says he saw the officer slip on a muddy flower planter, and go down to the ground. According to the D.A., Green took the opportunity to attack Bonaminio with a steel pipe, and then grabbed the officer's own gun, and used it on him.
As Bonaminio shouted "don't do it," the D.A. said Green fired three times. The third time, he was allegedly less than 2 feet from Bonaminio's head.
Then, just about two minutes after the traffic stop, the D.A. said Green got back into the truck he had apparently stolen, and drove off.
In the defense's opening statement, which lasted only a few minutes, they disputed almost none of it, saying that Green did, in fact, murder Bonaminio. But they want the jury to consider Green's state of mind, because of an argument he got into with his uncle the day before the shooting took place.