Chronic staff shortages, shortcomings in infrastructure and resources, and inadequate support capacity at Western Australia's Casuarina Prison is "undermining safety and security as well as the prison's ability to rehabilitate prisoners and prepare them to re-enter the community", says the state's Inspector of Custodial Services.

Eamon Ryan submitted two key reports to WA Parliament on Monday examining the state's largest publicly-run prison, Casuarina.

Indigenous people are drastically over-represented in Western Australia's prison system.

The reports cover the 2022 inspection and an in-depth review into the State's specialised high-security unit, the Special Handling Unit (SHU), located within Casuarina.

The inspection found the prison undergoing an extensive expansion project that will eventually make it the biggest in Australia with capacity for more than 1,800 men.

Mr Ryan said the new units and additional bed capacity had broader implications, noting that increasing complexity is associated with "managing so many people and their needs".

"The question has to be asked, 'how big is too big?' In addition to the mainstream units, Casuarina currently has a number of specialist units, including the SHU, a special protection unit, and the Mallee residential alcohol and other drugs rehabilitation unit. A high security unit is under construction while works for a forensic mental health unit, an expanded infirmary and a high dependency unit have yet to commence," he said.

"While I welcome these units as the services and care they will provide are desperately needed, the expansion comes with significant risks. Safely managing prisoners with so many diverse needs, conflicts and risks between them is a considerable challenge. Layered on top of this is the high prevalence of health and mental health needs, and intellectual and cognitive impairments within the prison population."

Mr Ryan said situation is exacerbated by "the lack of meaningful and constructive activity" in the daily regime, with high unemployment and underemployment.

"The inspection report shows that the infrastructure and resources to support meaningful prisoner activities like industries, recreation, education, and programs had not kept pace with the accommodation expansions," he said.

"Casuarina fundamentally lacked adequate support capacity. And this was undermining safety and security as well as the prison's ability to rehabilitate prisoners and prepare them to re-enter the community.

"Chronic custodial staffing shortages seen at the time of the inspection were an aggravating factor. The shortages, which were primarily driven by unplanned absences like personal and workers' compensation leave, meant staff were redeployed from other duties. Consequently, activities and services for prisoners were frequently restricted or cancelled.

"Throughout the inspection, prison officers cited short staffing as one of the main reasons for low morale."

Noongar legal academic and human rights expert Dr Hannah McGlade told National Indigenous Times the report indicated that "Casuarina's expansion has not been well thought out" and that the prison population has "high needs not being addressed".

"This, of course, leads to risks for both the detainees and staff," she said.

"We know that Medicare is not provided in prisons, and this is a serious problem as prisoner's complex health needs aren't being met.

"Also, Aboriginal men, including young men, make up a significant proportion of Casuarina inmates due to systemic discrimination and ongoing marginalisation of Indigenous peoples. The Justice department has not adequately ensured cultural safety for Aboriginal prisoners, and the high risk for remand and young prisoners, prisoners with mental health disability and prisoners who have experienced childhood trauma. All these factors increase risk of suicide and deaths in custody.

"Justice reinvestment approaches are urgently required, warehousing Indigenous peoples in prisons fails to address underlying drivers of crime and fails to reduce crime, and punitive laws and systemic incarceration fails Aboriginal people and wider society. Employment, education, health and housing are paramount issues that must be addressed."

The WA Department of Justice said it welcomed the reports.

"Casuarina has been undergoing a major expansion program… In addition to the mainstream prisoner population, it houses and supports adult prisoners across a number of specialist service units… (for detainees including) high-risk or major-threat adult prisoners in the Special Handling Unit (SHU) as well as those placed in protection units for their safety," a spokesperson said.

"OICS inspected Casuarina in September last year. It said Casuarina continued to be responsible for many of the State's most difficult-to-manage prisoners."

Corrective Services Commissioner Mike Reynolds said Casuarina management and staff had continued to operate the facility "effectively and efficiently" and address the challenges of an expanding and increasingly complex prison.

The Department noted the prison offers prisoners hoping to address alcohol and other drug addictions an opportunity to take part in a "therapeutic community" within its Mallee Rehabilitation Centre.

OICS highlighted the Mallee unit's success in helping treat adult prisoners' AOD issues since its inception in 2020.

"Its report said areas including the SHU, infirmary, confinement regimes and education were also well managed."

Department Director General Dr Adam Tomison said Casuarina held a "unique position" in the State's prison system.

"Casuarina management, staff and specialist service providers perform a critical role in handling the various risks and the OICS report acknowledges this," Dr Tomison said.

Mr Ryan said the review of the Special Handling Unit (SHU) examined all aspects of the operations, management and oversight of the 17-cell SHU and found that it was "generally managed well in challenging circumstances".

The review recognised that the "increasingly complex" cohort of prisoners being managed in the SHU – including a number of violent offenders with complex mental illnesses – had impacted the available time out of cell and ability for management to transition prisoners back into the mainstream population. The review noted that notwithstanding this, management were providing active case management and "proactively identifying ways to increase recreation and time out of cell".

Mr Ryan said that given the "complex matrix of risks" presented by prisoners in the SHU, the Office of the Inspector of Custodial Services recognised "the need for some restrictions and limits to the daily routine".

"Despite this, we found that the majority of prisoners on most days were receiving above the minimum required time out of cell."

Mr Ryan said that while in contrast with the first inspection of SHU conducted by the OICS in November 2000, the unit has "come a long way", concerns remain, particular regarding the length of time some prisoners have been kept in the unit.

"While many similar challenges remain, including the impact on prisoners of a significantly restricted regime, the SHU is a necessary and essential placement option for prisoners in Western Australia," he said.

"We were pleased to see management demonstrating a commitment to progressing prisoners out of the SHU by identifying and mitigating known risks. Still, four out of 10 prisoners spent more than a year in this restrictive environment. While we acknowledge the complex risks management are navigating, we continue to raise concern about the length of time some have remained in this unit."

Casuarina is also the site of youth facility Unit 18, which has been the centre of controversy since its establishment last July and last week 16-year-old Aboriginal boy Cleveland Dodd died in hospital days after being found unresponsive in his Unit 18 cell. The scope of the inspection did not include Unit 18, which is operated separately from the adult prison as a gazetted youth detention facility.