More than 1,200 people are detained indefinitely in Australia with no criminal conviction

More than 1,200 people with a mental impairment are being indefinitely detained in Australia, some for decades, without having been convicted of a criminal offence.

A Guardian Australia analysis has found every state and territory is detaining people using a variety of court orders that, in some instances, can result in a person being detained or subject to strict conditions for life.

People detained indefinitely without conviction are most commonly those who are found unfit to plead after being charged with a criminal offence, or who are found not guilty because of a mental impairment.

Information about the number and circumstances of detainees is difficult to establish because no national records are kept, and Australia has failed to meet its obligations under an international torture convention to provide for unannounced visits to places of detention.

Ben Buckland, a senior adviser at the Association for the Prevention of Torture, says that leaves the public in the dark.

Guardian Australia put questions about indefinite detention to each state and territory government. The ACT is the only jurisdiction that does not allow for indefinite detention.

Some declined to answer, referring instead to annual reports which contained data that was several months old.

Orders that allow indefinite detention in some jurisdictions can be removed or challenged at any time, making it hard to be precise about numbers at any given point.

But combining annual report data with the current data given by each jurisdiction this year shows that 1,215 people were detained or controlled under a court order.

For the purpose of the analysis, every individual subject to an order that allowed for detention was included, although some may be living in the community under strict conditions.

New South Wales detained 635 people in the 2021-22 financial year, compared with 324 in Queensland and 130 in Victoria.

One individual in Queensland had been subject to a forensic order for 42 years. Queensland Health and Queensland Corrective Services declined to comment on the case, but the majority of those in the state subject to forensic orders are not in detention.

The Northern Territory has 13 people with mental impairments indefinitely detained using custodial supervision orders, most of whom are in the Darwin Correctional Centre. One person has been on an order for more than 30 years.

There were 53 mentally impaired prisoners in the state as of 8 April, including 10 in prison, 26 detained in an authorised hospital, and 14 in the community subject to a conditional release order.

Before winning office, the premier, Mark McGowan, promised to end the indefinite detention of those considered mentally impaired. But more than six years later, no legislation has materialised. Individuals can spend longer in detention than they would have if found guilty of the crime they were charged with, rather than not guilty or being unfit to plead.

Under an international protocol ratified more than four years ago, an independent monitor is supposed to have oversight of all people in detention.

But Australia has repeatedly delayed implementing the changes to its detention regime required under the Optional Protocol to the Convention Against Torture, known as Opcat.

Signatories to Opcat must establish regular preventive visits to places of detention by independent bodies known as National Preventive Mechanisms (NPM).

The Victorian and NSW attorneys general wrote jointly to the former Morrison government last year saying they would be unable to meet the requirements of the Opcat without federal support. Queensland is understood to have made similar representations.

The federal attorney general, Mark Dreyfus, confirmed that Australia had received an extension for full compliance with Opcat until January.

Buckland says the protocol has had a strong deterrent effect in other countries where it has been implemented.