Inmates walk outside their cells at San Quentin state prison in San Quentin, California, June 8, 2012. San Quentin prison is California's oldest correctional facility and houses the state's only gas chamber. REUTERS/Lucy Nicholson

Marvin Caldwell, 63, who said he was imprisoned for 20 years under the three strikes law for possession and sale of methamphetamine, looks out of his cell at San Quentin state prison in San Quentin, California June 8, 2012. REUTERS/Lucy Nicholson

Marvin Caldwell, 63, who said he was imprisoned for 20 years under the three strikes law for possession and sale of methamphetamine, looks out of his cell at San Quentin state prison in San Quentin, California, June 8, 2012. . REUTERS/Lucy Nicholson

Inmates walk outside their cells at San Quentin state prison in San Quentin, California, June 8, 2012. REUTERS/Lucy Nicholson

Jimmy Merjil, 70, who said he was serving life under the three strikes law for petty theft, sits in his cell at San Quentin state prison in San Quentin, California, June 8, 2012. REUTERS/Lucy Nicholson

Albert Ruiz, 50, who is on death row for murder, is led down a corridor at San Quentin state prison in San Quentin, California, June 8, 2012. REUTERS/Lucy Nicholson

An inmate talks on the phone at San Quentin state prison in San Quentin, California, June 8, 2012. REUTERS/Lucy Nicholson

An inmate visits a dentist in the medical facility at San Quentin state prison in San Quentin, California, June 8, 2012. REUTERS/Lucy Nicholson

Inmates leave the exercise yard at San Quentin state prison in San Quentin, California, June 8, 2012. REUTERS/Lucy Nicholson

Chris Willis, 34, works out in the exercise yard at San Quentin state prison in San Quentin, California June 8, 2012. REUTERS/Lucy Nicholson

Martell Collins, 51, does push-ups in the exercise yard at San Quentin state prison in San Quentin, California, June 8, 2012. REUTERS/Lucy Nicholson

Chris Willis, 34, works out in the exercise yard at San Quentin state prison in San Quentin, California, June 8, 2012. REUTERS/Lucy Nicholson

Prisoners play table tennis in the exercise yard at San Quentin state prison in San Quentin, California, June 8, 2012. REUTERS/Lucy Nicholson

The entrance to death row is seen at San Quentin state prison in San Quentin, California, June 8, 2012. REUTERS/Lucy Nicholson

Albert Ruiz, 50, who is on death row for murder, is led down a corridor at San Quentin state prison in San Quentin, California June 8, 2012. REUTERS/Lucy Nicholson

Albert Ruiz, 50, who is on death row for murder, is led down a corridor at San Quentin state prison in San Quentin, California June 8, 2012. REUTERS/Lucy Nicholson

Administrative segregation prisoners take part in a group therapy session at San Quentin state prison in San Quentin, California, June 8, 2012. REUTERS/Lucy Nicholson

Cory Adams, 25, who said he was serving eight months for possession of a firearm and drugs, watches a movie from a cage in the medical facility at San Quentin state prison in San Quentin, California June 8, 2012. REUTERS/Lucy Nicholson

Cory Adams, 25, who said he was serving eight months for possession of a firearm and drugs, sits in a cage in the medical facility at San Quentin state prison in San Quentin, California, June 8, 2012. REUTERS/Lucy Nicholson

An administrative segregation prisoner exercises by jumping off a toilet in a cage at San Quentin state prison in San Quentin, California, June 8, 2012. REUTERS/Lucy Nicholson

Inmates walk in San Quentin state prison in San Quentin, California, June 8, 2012. REUTERS/Lucy Nicholson

Inmates are escorted by a guard through San Quentin state prison in San Quentin, California, June 8, 2012. REUTERS/Lucy Nicholson

Inmates walk through San Quentin state prison in San Quentin, California, June 8, 2012. REUTERS/Lucy Nicholson

San Quentin post office is seen outside San Quentin state prison in San Quentin, California, June 8, 2012. REUTERS/Lucy Nicholson