Stephen Seagar is used to seeing humans at their worst but even he was shocked by the hospital dubbed "Gomorrah".
Seagar, a US psychiatrist, has written a book, Behind the Gates of Gomorrah, about his last four years at the Napa state hospital.
His patients included serial killers and mass murderers who had been sent for treatment rather than to prison.
Seagar said it is a brutal place.
We have 3000 assaults a year in this hospital, major assaults, we've had staff and patients murdered, half the nurses in my unit have been off on disability, so it's a rugged environment.
Stephen Seagar said, after witnessing the violence against staff and patients first hand he now believes the facility shouldn't be a hospital and a prison at the same time.
While Seagar still works in the system he is a fierce critic of it and believes a radical shake of the secure hospital model up is needed.
"Our patients are generally found not guilty by reason of insanity and get sent here rather than to prison. But it just doesn't work, if it's a hospital you don't have guards, you either have to run it on a hospital model, or a penal model.
I don't think anywhere in the world has it right, it's a world wide problem, it needs to be a more penal model to be safe.
And his thoughts on a solution:
About 10 percent of the 1200 patients in the Napa State hospital commit 90 percent of the violence. We need to segregate out the worst offenders. That would go part of the way. It's hard for people who don't live in the US to believe this, we have murderers remanded into our care, they have to stay here, but they can refuse medication, so the whole process is really fouled up.
Behind the Gates of Gomorrah by Stephen Seagar, is published by Allen and Unwin with RRP $36.99
Seagar will be talking to Kathryn Ryan on Nine to Noon on Wednesday 11 February at 10.05am.