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.

Martell Collins, 51, does push-ups in the exercise yard at San Quentin state prison in San Quentin.

Chris Willis, 34, works out in the exercise yard at San Quentin state prison in San Quentin

Prisoners play tennis and table tennis in the exercise yard at San Quentin state prison in San Quentin.

The entrance to death row is seen at San Quentin state prison in San Quentin, California.

ory 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.

An administrative segregation prisoner exercises by jumping off a toilet in a cage at San Quentin state prison in San Quentin.

Inside San Quentin California’s oldest prison.

Inside San Quentin California’s oldest prison.