A jury found John Kirk McKinney, 30, guilty of the second-degree murder of Cecil Warren, 77, according to the Orange County district attorney's office.
McKinney's co-defendant, Curtis James Hill, 29, also of Huntington Beach, was found guilty Nov. 1 of special-circumstances murder in the commission of a robbery, and he was sentenced to life in state prison without the possibility of parole.
McKinney and Hill entered Warren's parked van about 4:45 a.m. Nov. 11, 2003, with the intention of stealing from it, according to prosecutors.
Warren, who worked as a handyman, noticed the men in his van while cleaning the parking lot of a bank in Huntington Beach.
When he confronted them, McKinney and Hill attacked him, prosecutors said.
They kicked Warren, hit him in the head, took his wallet, then left him on the ground and fled the scene.
About 30 minutes later, a pedestrian found Warren bleeding and called 911. Warren gave police a brief description before falling into a coma that lasted for three and a half years.
McKinney and Hill were eventually caught and were serving a prison sentence for the assault and robbery. They were set to be released until Warren died Sept. 22, 2007, from the head injuries he sustained during the attack, prosecutors said. They were charged with Warren's death on Sept. 4, 2009.
McKinney faces a maximum of 15 years to life in state prison and is scheduled to be sentenced June 15 in the Central Justice Center in Santa Ana.