Tower Controller described an unauthorized runway entry event by an aircraft experiencing radio equipment difficulties; the reporter listing CIC lack of experience and training as a causal factor.

Narrative

Cessna holding short of Runway 28R asked the Local Controller for take off clearance and pattern work. The developmental cleared the aircraft for takeoff; aircraft did not move nor acknowledged transmission. The developmental transmitted to the pilot if he heard the transmission cancel take off clearance and hold short instructions. Departures with other aircraft resumed. The Cessna reattempted same scenario occurred until about the third time the pilot transmitted he would like a green light to taxi back to the FBO; the Local Controller told the pilot if you here this transmission contact Ground for your request. Local informed Ground of the call sign and light gun request verbally and via notations on a flight progress strip. The Ground Controller issued a light gun signal and then the pilot proceeded onto Runway 28R. After the occurrence; I turned to the CIC and advised them that they needed to inform the FLM of the event. The CIC could have taken better initiative to be attentive to the needs and Ground Controller with the intentions of the pilot. The pilot needs to re-visit the AIM and review taxi procedure on movement areas. New CIC's need more training and supervision; once qualified; they sit in the back and tune out. I believe the training they receive is inadequate. CIC's need more training to gain knowledge and to fully understand the responsibility they hold and what vital role they play in the Tower Cab.