South Australia has the less-than-coveted title of being the last state in Australia with a so-called "gay panic" defence for murder.

That involves a non-violent sexual advance being considered enough reason to downgrade a murder charge to manslaughter.

Authors of the South Australian Law Reform report say the law known as "provocation" has been used four times in the past 10 years.

They say it often causes outrage when it is used, and they want it abolished.

Andrew Negre was killed after making a joking comment about gay sex. ( Supplied )

One such case was in 2011. Adelaide man Andrew Negre made a joke that another man, Michael Lindsay, should pay him for sex.

Lindsay subsequently stabbed Mr Negre to death and put his body in a wheelie bin.

Report author David Plater said there was no place for any so-called "gay panic" defence in today's society.

"This is the notion that where someone makes a non-violent gay advance at you, that this is sufficient in itself for someone in the 21st century to fly into a murderous rage and murder the person who made the advance," Dr Plater said.

"This is the use of provocation in what we consider and conclude from our report to be quite offensive and anachronistic in the 21st century."

Provocation law also 'discriminates against women'

Dr Plater said it comes down to the law's origins in the late 1700s and early 1800s where it was focused on issues around the concept of 'male honour'.

"It was very much designed to assist males, in situations in the 1800s of so-called male honour, typically where they discovered their wife was having an affair … or in situations where later developed, it was an imputation on male honour that someone had made a gay advance to them," Dr Plater said.

He said that has translated to a gender bias in today's law.

"In other words, it unduly favours — or is used by — violent and abusive men in circumstances such as a sexual affair or a relationship breakdown," he said.

"But it's very difficult to be used by female victims of family violence who might finally respond and kill their abusive male partner."

1981 murder case highlighted gender issues

In 1981 an Adelaide woman found out her abusive and controlling husband had been sexually abusing their four daughters for more than two decades.

That night she murdered him in his sleep with an axe.

She was originally found guilty and handed a mandatory life sentence, but on appeal, the court found the jury should have been instructed on provocation.

The report also calls for clarification of defences available in domestic violence cases. ( ABC News )

Her conviction was quashed and a re-trial ordered.

Domestic violence cases like these are one of the reasons there have been some arguments against getting rid of the provocation defence altogether.

But Dr Plater said there were other defences that could be used more effectively, such as self-defence and duress.

But he said they should be revised and clarified "to give greater protection and certainty to victims of family violence who might commit crimes as a result of violence or pressure from an abusive partner".

Call for mandatory murder terms to go

South Australia is one of only three Australian jurisdictions where there are mandatory life sentences for murder — with a minimum parole term of 20 years.

Removing the provocation defence gives courts one less way to get around those mandatory terms.

South Australia still has mandatory jail terms for murder. ( ABC News: Alkira Reinfrank )

Joint report author, former Supreme Court Justice David Bleby, said mandatory sentences were a "blunt instrument" that could make sentences unjust and unfair.

"Murder covers a whole range of homicide from things like mercy killing to mass shootings of innocent victims and gangland killings," he said.

"They're all treated the same when it comes to the head sentence and when it comes to the mandatory non-parole period."

Justice Bleby said taking away the provocation law would lead to longer sentences in similar cases unless mandatory sentencing is lifted.

"So that judges have a wider discretion to be able to take into account all sorts of relevant factors on the type of murder it is and any matters personal to the offender," he said.

"That's what judges do in every other type of crime but not murder," he said.

Will the Government adopt the changes?

The Attorney-General, Vickie Chapman, has already shown some support for the report.

She told Parliament that "gay panic" is "simply no longer acceptable" and she will consider her response to the report's recommendations.