Ash was a fellow gang member and potential witness to the killing. Prosecutors say Fajardo was concerned Ash might tell authorities about the murder.
In 2006, Green was killed when gunmen opened fire on a group of people in Harbor Gateway. She was African-American.
Investigators believe the shooting was part of an ongoing turf war between black and Latino gangs.
Fajardo's conviction included the special circumstances of lying in wait, gang killing, murder of a witness and racial motivation.
He will be formally sentenced in January.
Daniel Aguilar, 23, was also convicted of murdering Ash. Aguilar was sentenced to life in prison without the possibility of parole.
The Associated Press contributed to this report.