A psychiatric patient accused of strangling a Napa State Hospital employee pleaded no contest to a murder charge Tuesday.

Jess Massey, 38, entered his plea in Napa County Superior Court as part of a deal with prosecutors that will send him to prison for 25 years to life, the Napa Valley Register (http://bit.ly/qenrLl) reported.

Authorities said Massey attacked psychiatric technician Donna Gross on Oct. 23 on the hospital grounds and left her body behind a patio wall. He also was accused of robbing the 54-year-old woman of jewelry and $2 in cash.

The killing highlighted security concerns at the hospital, which houses patients from the criminal justice system.

In April, the California Division of Occupational Safety and Health fined the hospital more than $100,000 for six violations that contributed to Gross' death, including flawed alarm systems, inadequate police presence and no enforcement of existing safety policies and procedures.

Massey initially pleaded not guilty by reason of insanity.

Prosecutors and investigators said they believe Massey, who has a criminal history, was sane at the time of the killing. Massey was convicted of burglary in 1995 and admitted to the hospital in 1999 after being found not guilty by reason of insanity.

"I was always convinced that he was sane. I've always believed that he knew exactly what he was doing," Napa County Deputy District Attorney Allison Haley told the Register, noting that Massey tried to shift the blame to others for the killing.

In exchange for his plea change, prosecutors agreed to drop the kidnapping and robbery charges.

Massey is scheduled for formal sentencing on Aug. 23.