David John Grooms was responsible for a string of vicious assaults in the region spanning more than a decade, including the rape of a woman on a Wollongong train in 2008 and the bashing of two police officers at Warilla in 2015.

His four-year sentence for the latter offence officially expired on Thursday, prompting his release from prison.

However, Grooms’ movements are being closely monitored by parole authorities after the NSW Supreme Court in December ordered his strict supervision until the case is finalised.

During the proceedings, government lawyers asked Justice Robert Allan Hulme to make an order detaining Grooms for a further 18 months, claiming he posed an “unacceptable risk of committing another serious offence” if not kept in custody.

However, they said if the court was satisfied Grooms shouldn’t be detained, they were alternatively seeking he be strictly supervised for the next five years.

The court heard Grooms’ history of violence and aggression stemmed back to his teens, and was linked to his excessive drinking.

In 2004, Grooms was just shy of his 19^th birthday when he lashed out at bouncers and police during a drunken stand-off at a licensed premises. In 2007, he received a suspended prison sentence for intimidating and assaulting police after he was caught drinking in an alcohol-free zone.

A year later, in perhaps his worst offence to date, Grooms raped a female commuter on an early morning Wollongong train while inebriated. He served his entire 6½-year sentence behind bars.

His most recent jail term came about after he brutally assaulted two police officers at Oak Flats in 2015, leaving one with permanent facial injuries.

Grooms has also caused his fair share of disruption inside prison walls, racking up 19 disciplinary citations for fighting, intimidation, refusing to take drug tests or testing positive to drugs.

In 2010 he brutally bashed another inmate in a dispute over the line-up to use the telephone.

A risk assessment report prepared for December’s court proceedings put Grooms’ risk of violent re-offending at “high”, particularly in the context of his “anti-social and anti-authoritarian” attitudes.

“[Future offending may occur if] Mr Grooms encounters situations that he perceives to be confrontational or threatening or situations with persons in positions of power or authority, where he perceives provocation,” the psychologist who prepared the report wrote.

“Mr Grooms demonstrates anti-social and anti-authoritarian attitudes as reflected through current and historical offences against police.”

However, despite this assessment, Justice Hulme said he was not currently persuaded Grooms ought to remain behind bars and refused to order his ongoing detention – even on an interim basis.

“One the face of it, the present application is not among the strongest or more compelling of the many I have seen of its type,” he said.

“I am satisfied that the matters in the supporting documentation would, if proved, justify the making of an ESO [extended supervision order] but I’m not satisfied that there is justification for making a CDO [continuing detention order].”

He agreed to appoint two psychologists to examine Grooms and prepare detailed reports before a final decision is made.