When the naked and crumpled body of US maths genius Scott Johnson was found off Sydney's North Head, police dismissed his death as suicide. Nearly 20 years later, his family has launched its own investigation into the possibility the PhD student was the victim of a cliff-top killer targeting gay men, or even a gay-hate gang. The extraordinary theory is based on similarities between Johnson's death and the murders of up to six men, including WIN television newsreader Ross Warren, in Sydney's eastern suburbs between 1987 and 1990. In 2004 Coroner Jacqueline Milledge ruled that violent gangs preying on homosexuals probably hurled three of the group to their deaths at Marks Park, overlooking Bondi Beach. She also determined that gay bashings in the park were common and that similar attacks might have occurred at gay beats at Alexandria and Randwick. Spurred by the findings, Johnson's brother Steve has hired US investigative journalist Daniel Glick and retired NSW detective John McNamara to determine if the same scenario occurred on Sydney's northern beaches. So far their inquiries have focused on the rocky escarpment above Shelly Beach at Manly, which Johnson fell from in December 1988. Mr Glick, a veteran of 13 years with Newsweek magazine told The Sun-Herald he had been able to unearth more about the location during a 10-day visit than was ever aired at the 1989 inquest into Johnson's death. The Blue Fish Point lookout had, at the time of Johnson's death, been one of five well-known gay beats in the Manly area - a fact never disclosed by police, Mr Glick said. A 45-year-old Dee Why man told him he had been stabbed at the spot two years earlier but escaped. "What was happening at Bondi at this stage has been pretty well established. We know that," Mr Glick said while visiting the cliff-top on Thursday. "But you'd have to say the hypothesis, that this was also a place not immune from gay bashings, violence and even murder, is a reasonable one." Steve Johnson said his brother had "everything to live for". He had been told on the morning of his death that gaining his maths doctorate was a fait accompli. "I'm putting a fall, after some kind of a struggle gone wrong perhaps, at the top of the list," Mr Glick said. "Homicide would be second and, of course, suicide way down the bottom simply because, if that's the scenario, nothing quite adds up." In the '80s, detectives concluded the deaths of Warren and the two other men at Bondi were also misadventure. Ms Milledge described their findings as "inadequate, shameful and naive". Ref: Sydney Morning Herald (m)