British backpacker Caroline Stuttle was bashed and hurled screaming off Bundaberg’s Burnett River Bridge in April 2002 by Ian Douglas Previte.

Her shocking murder was followed by the sickening death of Michael Maher, who was burnt alive and bashed during a drinking session with killer Rodney Shane Rae in August 2003.

Just eight months later, 17-year-old Vlatka Mrmos was stabbed more than 40 times by Bojan Vulic as she sat in the passenger seat of her car in Brisbane’s south.

All three murders sent shockwaves across Queensland.

But now these killers could be freed under the state’s old parole laws, calling into question the adequacy of minimum non-parole periods.

Their possible release has prompted a call for Queensland to adopt “truth in sentencing” – a 1990s piece of NSW legislation that sees murderers sentenced to jail for “the rest of their natural life”.

“Let the bastards die in there, that’s what life should be,” Michael Maher’s stepfather Kerry Halter told The Sunday Mail.

In 2013, Queensland’s non-parole period was increased from 15 years to 20 years. But killers who were jailed before the change can still be released after serving 15 years.

Killers can be jailed “indefinitely”, but it is rare.

Vlatka Mrmos’ father Vladimir said Queensland’s parole laws still weren’t good enough.

Vlatka – a top student who wanted to study law – was due to start Year 12 at Macgregor State High School at the time of her murder, while Vulic was to begin teaching at John Paul College on Brisbane’s southside.

“I need (Vulic) to die, not to be released on parole,” Vladimir said.

“They said to me that it’s life, but it’s not life.”

Richard Stuttle, brother of Caroline, told The Sunday Mail that changing the non-parole period to 20 years was a step in the right direction.

But he spoke of his pain at learning his sister’s killer could walk free after just 15 years behind bars.

“To be honest we were shocked that 15 years was classed as a life sentence,” he said from his home in England.

“To knowingly take someone’s life in a manner that Caroline lost hers to me should mean the person responsible should give up theirs.”

It is understood Previte is eligible for parole now, Rae is eligible for in August and Vulic is eligible for parole in January.

In NSW, corrupt cop and killer Roger Rogerson was in 2016 jailed for the rest of his life following his execution of drug-dealer Jamie Gao in 2014.

Former Queensland detective turned criminologist Terry Goldsworthy said Queensland’s justice system was “finely balanced”.

“No system is perfect. We know in Queensland that 40 per cent of people reoffend within two years,” he said.

“As we know the sentence doesn’t always match the circumstances of the offence. But we have to leave some discretion up to the judges.”

A spokesman from Attorney-General Yvette D’Ath’s office said: “In New South Wales, while everyone convicted of murder is liable to be sentenced to life in prison, their courts can impose lesser maximum sentences should they wish.

“This isn’t possible in Queensland. Offenders have to serve their full sentence, and then need to apply for parole, which can be refused by the independent parole board.”