Wayne Ruks was not gay, says the woman who raised him as a single mother. His opinion was in fact that homosexuality was “unnatural” and he opposed same-sex marriage.

But it stands to be the Queensland man’s legacy that, through the extraordinary legal aftermath of his death, the archaic “gay panic” defence available to violent offenders will be finally struck from Australian law.

On Wednesday the Queensland government tabled a bill to strike down the use of “unwanted homosexual advances” as a cause of provocation by people who commit assault, manslaughter or even murder.

It is a hangover from old English common law that only Queensland and South Australia have so far failed to exclude by legislation.

The Queensland government reform, introduced in the last parliamentary sitting of 2016 and expected to pass early next year, follows promises by the South Australian premier, Jay Weatherill, to do likewise.

Both governments have finally responded to a tireless campaign by a Catholic priest, father Paul Kelly, in whose churchyard Ruks was found beaten to death in 2008.

One of his killers, Jason Andrew Pearce, argued during trial that Ruks tried to touch his crotch and sexually propositioned him – a claim at odds with CCTV footage from a camera that Kelly had installed.

The use of the gay panic defence was formally dropped but both Ruks’ mother, Joyce Kujala, and Kelly believe it influenced the outcome, which saw murder charges downgraded to manslaughter convictions. Pearce served four years of a nine-year sentence before getting out on parole in 2012. Richard Meerdink has applied for parole on his 10-year sentence.

Father Paul Kelly launched a Change.org petition to stop allowing ‘gay panic’ as an excuse for murder in Australia. His petition has attracted almost 290,000 supporters. Photograph: change.org

Kujala told Guardian Australia upon learning of the Queensland bill: “If my son brought this about through his death, at least there is some good that came out of it.

“I would say really if that stupid law didn’t exist these men would have got a lot more time for taking a life.”

Kelly said the bill followed years of lobbying, including of three different Queensland governments, despite all other states bar South Australia moving on the issue a decade ago.

“It’s been a massive effort, unfortunately,” he said. “At one point both sides [of politics] were sort of saying, aw no, the law didn’t exist and doesn’t need changing – but suddenly everyone’s saying it is a problem and does need changing, so that’s good to hear.

“This is as far as we’ve ever gotten and I’m fairly confident it will [pass]. Apparently the LNP have committed as well to support it.”

Kelly said his campaign came after following the Ruks murder trial and being astonished at why the judge had not “howled down” the use of the gay panic defence.

He said Kujala had “rightly picked up that this was perjorative and somehow going against the victim” and the fact she was forced to publicly clarify her son’s sexuality after his death beggared belief.

When the gay panic defence was again raised in the case of the bashing death of hitchhiker Stephen Ward, found in bushland near Kelly’s Maryborough church just six months later, the priest decided it had “gone too far”.

Kelly eventually started a petition on Change.org that went on to attract almost 290,000 supporters, one of the largest in the site’s history.

His petition prompted a post from Weatherill in May pledging to abolish gay panic as provocation. Kelly said he looked forward to the South Australian government following Queensland “swiftly” in kind.

Yvette D’Ath, the Queensland attorney general, had Kelly at her side when announcing the reform bill on Wednesday.

Kelly says when he began the petition he “actually expected 100 people”.

“When it took off I hadn’t seen anything like it and it really opened my eyes the power of the community. But in some ways it was a no-brainer. The fact it’s taken so long sends a message. But that this law’s being changed now sends another message that the law is the same for everybody. It’s not going to give certain members of the community less protection from violence.”

Queensland attorney general Yvette D’Ath (middle) with father Paul Kelly on Wednesday during the announcement of the Queensland government’s reform bill. Photograph: change.org

The Queensland Greens spokeswoman Kristen Lyons applauded the move to “take the hate out of our judicial system” a week after the state was forced to mourn the death of 13-year-old Tyrone Unsworth, “another young person driven to suicide after suffering bullying because of their sexuality”.

Emile McPhee, the director of the LGBTI Legal Service, said the long-awaited reform “sends a welcome message of acceptance to the Queensland LGBTI community, showing that Queenslanders will not accept violence on the basis of sexuality”.

The irony that the plight of Ruks, who was hardly an advocate for legal equality for gay men, is nevertheless poised to bring this about is not lost on Kujala.

“It’s not a question of homosexuality here, it’s a question of what you say to a person,” she said.

“The CCTV footage didn’t show my son making any advance. You’ve got a defence lawyer who brings in an old law on his say so without any advance whatsoever but on their word that something happened.”

Kujala was close to her son, a handyman on a disability pension. She was developing an acreage with him as “our assignment together” when he was killed.

He was about to move south to be closer to her. Kujala last spoke to him on the phone. Three days later police knocked on her door. She drove through pouring rain to Nambour to identify his battered body. He had bled out after being left for dead.

“Time doesn’t heal to any great degree when it comes to murder,” Kujala said.

But with the Queensland reforms now before parliament and South Australia’s presumably to come, “there’s a little bit of an opening of promise now”.

“I never thought the day would come that my son had to die to bring about a change of law.”