SAN FRANCISCO -- State prosecutors asked the California Supreme Court on Sunday to dismiss former gang leader Stanley Tookie Williams' latest petition to block his Tuesday execution for murdering four people in 1979.

The stay request filed on Williams' behalf "is without merit and is manifestly designed for delay," Deputy Attorney General Lisa Brault wrote the justices.

Brault's brief came hours after a lawyer for Williams, 51, urged the state Supreme Court to call off the Crips co-founder's upcoming death by lethal injection. The petition lodged late Saturday contended that Williams should have been allowed to argue at his 1981 trial that someone else killed one of his four alleged victims.

The petition, by Pasadena attorney Verna Wefald, also challenged the validity of Williams' four capital murder convictions. The justices days ago denied a request by Wefald to reopen the case based on allegations that shoddy forensics linked a weapon used in three of the murders to a shotgun registered to Williams.

Defense lawyers on Sunday also awaited Gov. Arnold Schwarzenegger's decision on whether to grant Williams clemency. They have asked the governor to spare the condemned man's life with the claim that Williams, who has written several children's books extolling the evils of gang life, has redeemed himself during 24 years at San Quentin State Prison.

Schwarzenegger has denied clemency to two other prisoners since he was elected in 2003, but said last week he was agonizing over what to do in the Williams case. The last California governor to grant clemency was Ronald Reagan, who spared a mentally ill killer in 1967.

Williams was convicted of shooting Albert Owens to death during a convenience store robbery on Feb. 27, 1979. He also was convicted of the March 11, 1979, murders of motel owners Yen-I Yang and Tsai-Shai Chen Yang and their daughter, Yu Chin Yang Lin, at a South Los Angeles motel.

Williams denies committing the murders but has apologized for co-founding the Crips, a gang prosecutors blamed for thousands of murders in Los Angeles and beyond.

In the petition filed Saturday, Wefald told the justices that Los Angeles County prosecutors failed to disclose at trial that witness Alfred Coward was not a U.S. citizen and that he had a violent criminal history.

The failure resulted in "depriving Williams of the opportunity to mount a defense" that Coward was Owens' killer, Wefald wrote.

Coward is now in prison in Canada for the murder of a man during a robbery.

"All of the witnesses who implicated Williams were criminals who were given significant incentives to testify against him and ongoing benefits for their testimony," Wefald wrote.

Wefald's request for an emergency stay also says a bill calling for a death penalty moratorium in California is scheduled to be heard in the California Legislature in January.

The California Supreme Court, a federal district court judge in Los Angeles, the 9th U.S. Circuit Court of Appeals and the U.S. Supreme Court have upheld Williams' convictions in earlier appeals.

"Because there is no justification for further delay in effecting the final judgment in this case, which has been repeatedly affirmed over the course of two decades, the stay request must be denied," Brault wrote.