A USC public safety officer's car can be seen on video passing the crime scene seconds after Ji managed to get up.

He staggered home, trailing blood the whole way. His roommate found him dead in bed the next morning.

It will never be known why he didn't seek help, but a coroner testified he likely would have died from the wounds even if he got help, McKinney said.

``He suffered the most significant brain injury, so it's hard to believe that his judgment wouldn't have been compromised at some level,'' said McKinney, who also suggested an alternate explanation. ``He was someone who extends a helping hand to others more than he seeks a helping hand. He may have been in a position where he thought he could take care of this himself.''

A couple hours after the beating, the four went to the beach, where Garcia, Ochoa, Guerrero allegedly robbed a tourist and attacked her friend.

Ochoa and Guerrero face robbery, attempted robbery and assault with deadly weapon charges related to that attack.

Del Carmen and Garcia could face the death penalty if convicted. Ochoa and Guerrero are charged as adults, but they can only face up to life in prison without the possibility of parole if convicted because of their ages.