Oscar-winning actor Jamie Foxx is among a number of high-profile stars calling for clemency for reformed gang leader Stanley "Tookie" Williams.
Williams has become a reformed character since entering jail
Foxx, who starred in a dramatisation of Williams's life, protested against Williams's planned execution at the premiere of his new film Jarhead.
Last week rap star Snoop Dogg spoke at a rally at San Quentin prison saying Williams's voice "needs to be heard".
Williams, 51, was sentenced to death in 1981 for the murder of four people.
Co-founder of the notorious Los Angeles Crips street-gang, Williams denies committing the 1979 murders that put him on death row.
He faces death by lethal injection on 13 December 2005.
While in jail, Williams has won praise for his anti-gang books, earning several Nobel Peace Prize nominations for his teachings.
Snoop Dogg attended a rally for Williams at San Quentin State Prison
His supporters range from Foxx and Snoop Dogg (himself a former Crips member) to Bishop Desmond Tutu and the Reverend Jesse Jackson.
They hope to persuade California governor Arnold Schwarzenegger that Williams can do more for society alive than dead.
When the Williams' biopic Redemption aired on US television last year, Foxx said: "If Stan "Tookie" Williams had been born in Connecticut in the same type of situation, and was a white man, he would have been running a company."
"But, born a black man who has the capability of having brute strength and the capability of being smart in the ways of the world, he's going to get into what he gets into."
But US prosecutors said Williams was a "cold-blooded killer" who did not deserve "atonement" for his "brutal, murderous acts".
Foxx stars in Sam Mendes war drama Jarhead with Jake Gyllenhaal
The crimes Williams was accused of were "heinous," said former MASH star Mike Farrell, who has lobbied for him for several years, but insists he has made"an extraordinary transformation".
Russell Crowe and Harry Belafonte are among the signatures Farrell has collected calling for clemency for Williams.