Berkley is a rival of Zero, a San Fierro electronics expert, which means Berkley is possibly also expert in electronics. The two each own their shop (Berkleys RC and Zero RC), although their rivalry goes back to when Zero won the top prize at a science fair. It is likely that both run their business in San Fierro.
Events of GTA San Andreas
The two are, in 1992, involved in a war involving remote control vehicles. Berkley, having just returned to San Fierro, launches 'a full scale attack' on Zero's shop and transmitters. Berkley's delivery men and vehicles are then targeted by Carl Johnson, and then defeated in a remote control army battle. After losing the battle, Berkley is told to pack up his business and leave San Fierro.
The whereabouts of Berkley are unknown, although he continues his rivalry with Zero, despite his business being strongly weakened by Carl and Zero's actions. Later, he is informed by Zero of the casino heist planned by Carl Johnson, Wu Zi Mu and the San Fierro Triads at the Caligula's Casino in Las Venturas. He alerts the authorities, who storm the casino just as Carl is escaping, making the job harder as the authorities manage to put back the lights on after Carl shut it down to make infiltration easier. Berkley, however, is unsuccessful, as CJ and his team manage to escape the SWAT response units sent at the area and arrive back at the Verdant Meadows airstrip with all the money. Carl then punches Zero for what he did. Berkley is then never mentioned again after the Caligula's heist.