Mentally disordered offenders (referred to as MDOs) are California state prison inmates who suffer from severe mental illness. And while it is believed that more than half of all state jail and prison inmates are affected by mental illness, MDOs only make up a small percentage of this population.
This is because the phrase “mentally disordered offenders ‘MDOs’” is a very technical one. People who suffer from illness such as depression, personality or adjustment disorders, mental retardation, drug and/or alcohol addiction, or many other relatively common mental diagnoses are excluded from the MDO class.
MDOs are exclusively offenders whose severe mental disorders caused (or largely contributed to) the offense for which the individual was imprisoned, whose condition can’t be kept in remission without treatment, and who present a substantial risk of reoffending based on their disorder.
These prisoners have their own set of California parole laws that, when necessary, prevent an individual who would otherwise be eligible for parole from ever being released.
"severe mental disorder" as used in this section does not include a personality or adjustment disorder, epilepsy, mental retardation or other developmental disabilities, or addiction to or abuse of intoxicating substances