The 2011 report by the state's own consultant runs counter to claims by Gov. Jerry Brown the state's prisons should be removed from federal oversight because inmates now receive good care, the Los Angeles Times reported Thursday.
State officials attempted to destroy the report by Lindsay Hayes, a national expert on suicide prevention in prisons.
He found the state held suicidal inmates, clothed only a "safety smock," for long periods in dirty airless cells with unsanitized mattresses on the floor.
Hayes reported that such conditions only compounded the risk they would take their own lives. He concluded inmates would tell guards they were no longer suicidal so escape the cells, only to commit suicide hours or days later.
Hayes' report said guards, not mental health workers, decided the conditions of suicide watchers.
In a 2012 e-mail to the consultant, prison official Robert Canning said the report had been "buried."
The state asked a federal court to destroy the report after attorneys for inmates obtained a copy. The court refused.
Hayes was hired by prison officials in 2010 to conduct a three-year study on suicide prevention to demonstrate the state's intention to improve mental health care for inmates.