Former gang leader Stanley Williams is scheduled to be executed in the early hours of Tuesday 13 December. He was sentenced to death in 1981 for a total of four murders carried out during two robberies in 1979.

While on death row Stanley Willliams has completely transformed himself, repudiating his past acts and violent lifestyle and dedicating himself to educating young people about the dangers of gang life.

Amnesty International UK Director Kate Allen said:

“Mr Williams’ violent past is well known but he is a textbook version of rehabilitation and to now execute this man would be a travesty of justice.

“We are calling on Governor Schwarzenegger to halt Tookie Williams’ execution in recognition of his own rehabilitation and his positive influence on others.”

Stanley Williams, one of the founders of the notorious "Crips" street gang in Los Angeles, California in the early 1970s underwent what he describes as a "redemptive transition" in prison, renouncing gang life and working to educate young people about its dangers.

Since coming out of solitary confinement, his behaviour record in prison has been exemplary.

He has written a series of Children's rights's books about the dangers of gang life, has been nominated for a Nobel Peace Prize for his work every year since 2001, and in 2005 received a US presidential service award from the President's Council on Service and Civic Participation.

Stanley Williams has also always maintained his innocence of the crimes for which he has been condemned to die.

According to his clemency petition, the case against him rested on testimony from accomplices in the crime and informants who were facing imprisonment or the death penalty for various offences, but who all received reduced sentences or freedom in exchange for their testimony.

There are also concerns about racial discrimination within the trial process itself. Williams was tried in an area where only one per cent of the jury pool was black. The trial prosecutor removed all Afro-Americans from the jury and on one occasion compared Williams - who sometimes appeared in court in shackles - to a Bengal tiger.

In January 2005 California Governor Arnold Schwarzenegger announced plans to remodel the focus of the prison system away from punishment towards rehabilitation.

In its 2004 ruling, the California Ninth Circuit Court of Appeal said that Stanley Williams’ "good works and accomplishments since incarceration may make him a worthy candidate" for an act of executive clemency.

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