Prisons fail mentally ill: top judge

Mentally ill people who would once be treated in hospital are "committed" to prisons as the criminal justice system fills a vacuum left by policies favouring treatment outside institutions, WA's top judge says.

WA Chief Justice Wayne Martin told the Rural and Remote Health Conference in Northam last week that research suggested that policies of "deinstitutionalisation" since the big Australian mental hospitals closed about 30 years ago had resulted in many people being "reinstitutionalised" in jails.

"For many, one form of institutionalisation has been replaced by another," Justice Martin said.

He said some people were detained indefinitely because their mental illness or disability made them incapable of the behaviour a structured, disciplined society demanded.

Though the crimes of some were so serious or they posed such as risk that detention was appropriate, there were possibly mentally ill offenders who were more a nuisance than a threat.

Justice Martin said people who were a nuisance should be diverted to treatment within society.

"It is important to steadfastly bear in mind there are real limits on what the criminal justice system can and should seek to do in relation to people who are mentally unwell or intellectually disabled," he said.

The criminal justice system was not always appropriate and certainly did not have the resources to cover for institutional and other supports for mentally ill people withdrawn 30 years ago.

In a snapshot of Perth's mental health court, a $4.5 million pilot scheme that began in March, Justice Martin said that in its first four months, 169 offenders faced more than 450 charges.

Nearly a third offended against justice procedures and government operations, such as breaching restraining or community- based orders and resisting public officers. Property damage (20 per cent), theft (almost 25 per cent) and violence (almost 15 per cent) were the other main categories.