Western Australia's most violent criminals may be kept behind bars beyond their sentence under new laws operating the same way as laws used to keep dangerous sex offenders in jail indefinitely.
The legislation passed on Wednesday night and is scheduled to come into effect on September 1.
The Director of Public Prosecutions or State Solicitor's Office will be able to ask the Supreme Court to order continuing detention or supervision of a seriously violent offender who continues to pose an unacceptable risk of reoffending at the end of their sentence.
"This will include members of outlaw motorcycle gangs, offenders convicted of kidnapping, robbery, and grievous bodily harm, as well as additional sexual offences including those involving child exploitation material," Attorney-General John Quigley said on Thursday.
The DSO laws, introduced in 2005, were largely inspired by psychopath Garry Narkle, who has a 40-year criminal history of violent sex attacks against children, women and a 38-year-old homeless man, and remains in jail.
Mr Quigley said only one DSO has reoffended while subject to an order, referring to Mark Bradley Wimbridge, who has a history of sexual offending of more than 30 years and raped a woman after being released from jail in 2016.
It's understood the new High Risk Serious Offenders Bill has not been inspired by any particular criminal.
As with DSO laws, those released under a supervision order will be subject to conditions including GPS tracking, while foreign offenders could instead by deported back to their home country.