Ernest Allen Head - described by friends as a soft-hearted, shy and good-natured man - was found dead in his Summer Hill apartment in June 1976.
The 48-year-old died in a "frenzied" attack during which he was stabbed 35 times on his body and face.
A NSW inquiry was told the nature of the attack and the extent of Mr Head's injuries could indicate the crime was motivated by gay bias.
A special inquiry is investigating unsolved suspected hate crime deaths of LGBTQI people in NSW between 1970 and 2010, including whether the attitudes of police officers impacted investigations.
While Mr Head had been in relationships with men and his brother knew he was gay, he was not "out" in all contexts.
Initial police investigations into Mr Head's death were thorough, including pursuing multiple lines of inquiry and interviewing more than 100 people, but officers were unable to identify any suspects or persons of interest.
Three bloody palm prints were found near his body and a forensic breakthrough has allowed the current inquiry to identify a suspect.
At the time of the investigation, fingerprints were examined with a magnifying glass, however modern analysis involved digitally enhancing the prints.
NSW Supreme Court Justice John Sackar is overseeing the inquiry as commissioner.
A fresh analysis was ordered by the inquiry in April 2023, which revealed a match to a man named Engin Simsek.
Searches revealed that at various points between 1970 and 1992 Mr Simsek lived on the same street as Mr Head, as well as other addresses in Sydney's west.
Mr Simsek departed Australia for Turkey in August 1994 and died by suicide in 1999.
It is not known whether Mr Simsek was gay or bisexual and the inquiry did not find evidence he had a relationship with Mr Head.
Counsel assisting the inquiry Kathleen Heath said it was impossible to know whether Mr Head was killed by a lone assailant or multiple attackers.
But the forensic match of Mr Simsek's palm print was significant evidence, she added.
"The presence of Mr Simsek's palm print in blood on the kitchen wall above Mr Head's body powerfully indicates that (he) was at least involved in the events surrounding Mr Head's death," she said on Tuesday.
"Having regard to the position of the palm print in close vicinity to Mr Head's naked body and surrounded by blood marks ... it is submitted that the only reasonable inference is that the palm print was deposited at or shortly after the time of Mr Head's killing."
Ms Heath said the circumstances leading up to Mr Head's death, including whether he and Mr Simsek had sexual intercourse, were unknown.
Penile and anal swabs taken from Mr Head's body at the time, as well as a handkerchief, several cigarette butts and human hair found at the scene, have since been lost.
Ms Heath said a majority of relevant exhibits from the initial police investigation were now missing, resulting in the loss of significant forensic testing opportunities.
"It should have been obvious by reference to technology of the day, including blood typing technology, that at the very least the handkerchief should have been retained as evidence, if not also the cigarette butts and the human hair," she said.
"The loss of exhibits was not consistent with proper police practice, including judged by the standards of 1976."
Lifeline 13 11 14
beyondblue 1300 22 4636
Fullstop Australia 1800 385 578
21°C