A breakthrough arrest in the alleged murder of a gay American man in Sydney three decades ago has raised hopes of solving other violent homophobic attacks from that era, Australian police said Wednesday.

Australian man Scott Phillip White, 49, was arrested and charged Tuesday with the murder of US mathematician Scott Johnson, whose body was found at the base of a cliff in Sydney's north in December 1988.

Johnson's death was initially ruled a suicide, but a 2017 inquest found it was likely the 27-year-old had been either pushed over the cliff or fell while trying to escape assailants.

New South Wales police said White's arrest provided hope that other cold case killings could yet be solved -- in particular four deaths long-believed to be gay hate crimes.

"I'm very, very hopeful that results like this reverberate through the community and we can get more information -- that's what we need, we need more information in order to pursue these cases," assistant police commissioner Tony Crandell said.

"They're not closed, they're not frozen, we will work on them and anybody out there who's committed such offences should be looking over their shoulder."

US mathematician Scott Johnson died more than 30 years ago
US mathematician Scott Johnson died more than 30 years ago NEW SOUTH WALES POLICE / Handout

At the time of Johnson's death, gangs roamed Sydney searching for gay men to attack and were known to rob or assault men at "gay beats" across the city.

Police later reclassified 27 deaths between the 1970s and 2000 as homophobic hate crimes, though Crandell said he believed the number was likely to be far higher.

"There may well have been many others -- in fact, I'm sure there were many others," he said.

The force admitted in 2018 that it had played a part in marginalising the LGBT community and enabling society's "acceptance of shocking violence directed at gay men" during the period.

"I do think the plight of young gay men in Sydney, and probably around the world, was a very difficult one and not only were they let down by police, they were let down by the community and probably the media," police commissioner Mick Fuller said Wednesday.

White did not apply for bail at a court hearing Wednesday and was remanded in custody. His next court appearance is scheduled for July.