Tucked away in the personnel files of the University of Adelaide is a 48-year-old beige folder, containing a job offer to a law lecturer named Dr George Duncan.

At first glance it looks like just another piece of colourless bureaucracy — the kind of thing churned out daily by every organisation's HR department — but in this example, appearances are deceptive.

The university's executive dean John Williams, said the plain folder changed Australian law, and transformed the lives of gay men.

Dr Duncan's job offer would lead him to his death, but ultimately push South Australia into enacting the country's first homosexual law reforms.

"In a document that starts in a very small moment about someone accepting a job, we can see and project a whole different Australia … the society Australia is today," Professor Williams said.

"It's from this moment that a whole change occurred in the way that we saw equality, how the law for gay Australians would be framed.

"It ultimately led to this big question of the equality in marriage vote in Australia, in 2017."

'Left a legacy that's changed us'

The tale of how a job offer resulted in such dramatic changes started in 1971.

The University of Adelaide found itself short of a law lecturer and advertised to fill the position.

George Duncan's employment file from the University of Adelaide from 1971, the year before he was killed. ( ABC News: Simon Royal )

It soon settled on an application from Dr Duncan, who was born in Melbourne, but spent much of his life in the UK.

Duncan arrived in Adelaide in March 1972. Barely more than a month later, the law lecturer was dead.

Dr Duncan, who was gay, drowned after being thrown into the River Torrens, not far from the university.

The banks of the Torrens were the site of a gay beat — well known to both gay men and also SA Police's Vice Squad.

In the early 70s, male homosexuality was still illegal in every Australian state and territory, and policing it was under the Vice Squad's brief.

The hothouse world of Adelaide's political, legal and media circles soon started swirling with rumours and indeed, reports, of police involvement in Duncan's death, as some officers were known to target gay men.

Eventually, two Vice Squad members were tried and acquitted of Duncan's manslaughter.

By that time though, the outcry and outrage over Duncan's death had resulted in a bipartisan push in SA's Parliament to decriminalise homosexuality under Don Dunstan's Labor government.

Professor John Williams is executive dean of the University of Adelaide. ( ABC News Simon Royal )

It was the first success on a long road towards reform throughout the country, with Tasmania being the last state to change its laws in 1997.

However, Professor Williams believed memories of George Duncan's death — the tragedy that sparked those changes — had faded.

It is one of the reasons why, for the first time, he has chosen to publicly reveal the law lecturer's employment file.

"Dr Duncan only touched us lightly … he was in Adelaide for just six weeks," Professor Williams said.

"But what happened to him, and the reaction to that, left a legacy that's changed us.

"The university was, thankfully, always going to keep Dr Duncan's file, but I think there's now a place for us to get it into a wider collection where we bring together the strands of Dr Duncan, so we can give a concentration to the life of this man."

Little evidence of him remains

Pulling together the strands of George Duncan's interrupted life is something historian Tim Reeves has devoted much of his professional life to — and it has proved a challenging task.

The "light touch" Duncan left on Australia means very little physical evidence of him remains — his university employment file, a single black-and-white photo, and one battered suitcase, are about it.

Adelaide historian Tim Reeves has written about the case of George Duncan. ( ABC News: Simon Royal )

Mr Reeves has been searching for that suitcase which was apparently kept in police storage on the coroner's orders.

"I think it's an incredibly important artefact," he said.

"It contained some personal papers and other items … it's one of the few things left after Dr Duncan's death.

"I wrote to the Coroner's Office in 2015 to see if we could use the suitcase in an exhibition … and that's when I got the response that it was missing. I was expecting it to be there and it wasn't."

Exhibits destroyed by police

Early this year, the ABC requested a new search be made for Dr Duncan's suitcase.

The Coroner's Office finally resolved the mystery detailing the case's fate in an email.

"On 11/1/2012, the following exhibits were destroyed — a suitcase, toiletries, a photograph, travel books, insurance forms, academic correspondence, legal documents and banking statements," the email said.

They were authorised for destruction by the Major Crime Investigation Branch.

In the same email from his office, the outgoing coroner Mark Johns lashed the police decision.

"The coroner has emphasised he was not aware of the intention to destroy the property … he would normally be consulted before the destruction of such an item … had he been asked he certainly would not have authorised, or agreed with destroying the items," the statement said.

Duncan's death was major news and eventually led to decriminalisation of homosexuality.

Tim Reeves and John Williams believe the destruction of the suitcase was nothing more than a bureaucratic bungle, but was certainly not a good look, given the unfortunate history of SA Police and the Duncan case.

"One would have thought they'd have gone out of their way to make sure nothing untoward happened to the one item that remained of Duncan after his death," Mr Reeves said.

"I fear this was just a normal administrative failure where nobody appreciated just what they had … they've missed a moment, which is sad," Professor Williams added.

Along with the beige employment file, the suitcase would have helped highlight a crucial moment in Australia's journey towards a more inclusive society.

"There's a lot that people need to remember when they celebrate what we have now," Tim Reeves said.

"We don't make enough of what Duncan's death led to … I think there are a lot young LGBTQI people around Australia who don't realise that what they have now all started on the banks of the River Torrens in 1972."