Decisions on whether to spare convicted killers such as Williams from execution "are very heavy responsibilities", he said.
An international campaign has been launched to save Williams, on death row
for the past two decades, and now a prominent activist against gang violence.
Prosecutors and defence lawyers each had 30 minutes to plead their cases for
and against giving Williams lethal injections in San Quentin Prison on
December 13.
Williams, now 51, was a co-founder of the notorious Crips gang that terrified Los Angeles in the 1970s.
He was found guilty in 1981 of the shotgun murders of four people during two robberies.
About 100 opponents of the death penalty gathered outside the governor's
office in Sacramento, as the hearing went ahead.
A letter that Williams wrote to Governor Schwarzenegger was presented at the
meeting.
"We were allowed to say what we wanted to say," Peter Fleming, representing the six defence lawyers, told reporters after the hearing.
When asked about the chances of winning clemency, Mr Fleming said, "I am not an odds-maker," adding "I am still frightened to death."
Los Angeles county Deputy District Attorney John Monaghan led the team
intent on convincing Governor Schwarzenegger that Williams deserved to die.
"This has nothing to do with redemption," Mr Monaghan said, scoffing at the notion Williams had shunned his legacy as a founder of the notorious Crips gang in Los Angeles.
"The evidence in this case is truly overwhelming," he said, expressing certainty Williams was guilty of brutally murdering four helpless people. "It simply justifies the ultimate punishment."
Williams' supporters, including activist Jesse Jackson, have lauded Williams as a role-model for young people susceptible to joining gangs.
The defence team said it has received more than 100,000 letters and e-mails contending that Williams' anti-gang message is reaching city streets and juvenile detention facilities, Mr Fleming said.
Williams has written books designed to convince children and youths to shun
gangs.
Williams' transformation has earned several nominations for the Nobel Peace
Prize.
The appeal to the Governor was not a claim of innocence, but a bid for mercy, according to his lawyers, who want Williams' sentence commuted to life
in prison without parole.
Governor Schwarzenegger's office said that a decision in the case would be announced in the next few days.