An outback police officer says his gut feeling led him to investigate a supposedly "freak accident", which ended with a former policeman convicted of murder.

Sergeant Gerry Thornton received little help from his colleagues when he investigated Lainie Coldwell's death in Charleville in south-west Queensland in 2009.

She died two days after sustaining a blow to the back of the head at the hands of her de-facto partner Louis James Mahony, a former constable with the Northern Territory Police.

Now nearly a decade after her death, Sergeant Thornton's intuition and dogged pursuit of the case has been recognised by the Queensland Police Service.

Louis James Mahony, Lainie Coldwell and their daughter ( ABC News )

Emergency services found Ms Coldwell at the base of a large gum tree with severe head injuries.

Mahony had been home at the time with their daughter and told emergency services she had fallen after trying to remove party lights.

Charleville police accepted Mahony's explanation and ruled the death as accidental.

Little evidence was taken from the scene, including an antique iron with blood on it.

Her life support was turned off on August 25, 2009 and her organs were donated.

She left behind her three-year-old daughter, and the grieving Charleville-based Coldwell family.

'Nothing looked right'

Eighty kilometres away, at the tiny two officer police station of Morven, officer-in-charge Gerry Thornton heard of the accident.

Lainie Coldwell's death was originally believed to be a freak accident. ( Supplied: Queensland Police )

Married to a Charleville woman himself and with five years already in the Morven district, Sergeant Thornton was immediately interested.

He happened to be visiting Charleville the day after Ms Coldwell's accident and made a point of driving past the house where a ladder was still standing on the back of Mahony's ute, leaning against a large lemon-scented gum tree.

He said he stopped to take it all in.

''Nothing looked right," he said.

"To me it wouldn't have been possible for anyone to dismount the ladder or even actually climb the ladder without it tilting.

"Two weeks later I was back up there [in Charleville] and I found out Mahony had taken out $2.25 million in life insurance in the two months prior to the incident.

"I said to an officer that we really need to look at it, but he basically said our hands were tied because the pathologist said her injuries were consistent with a fall."

Dogged persistence

Police Commissioner Ian Stewart on Wednesday acknowledged Sergeant Thornton's solo investigations were the reason the case was reopened in 2011, and eventually taken to trial last November.

Commissioner Ian Stewart praised Sergeant Thornton's work. ( ABC: Amy Phillips )

"When someone can't speak for themselves, and in this case it was Ms Coldwell, when they don't have a voice anymore and we have officers like this who are persistent, resilient and know what's right and are tenacious in tracking the evidence and bringing together of the brief — I think that's exceptional," he said.

Mahony was sentenced to life in prison with eligibility for parole in 13 years' time.

At the conclusion of the trial the Coldwell family were insistent the result was due to the dogged persistence of Sergeant Thornton.

Ms Coldwell's niece Georgia Grant spoke to media outside the court.

"[He] has devoted the past eight years to ensure we have justice for Lainie, for this case would have remained cold and justice not served," she said.

Lainie Coldwell's niece Georgia Grant said without Sergeant Thornton justice wouldn't have been served. ( ABC News )

Good old-fashioned policing

Sergeant Thornton is quick to deflect the accolades, instead wanting the bravery of the Charleville people who offered witness statements to be recognised.

They are statements he spent endless nights collecting over the phone while sitting on the front veranda of the Morven police house.

"They were all salt of the earth people," he said.

"A large portion of them worked at the abattoir.

"I wouldn't imagine more than three or four per cent had ever been into a court, let alone a Supreme Court, so they were incredible."

Louis James Mahony was jailed for life for Lainie Coldwell's murder. ( Supplied: QPS )

He says cracking the case came down to good old-fashioned policing where knocking on doors and speaking to locals led the investigation in the right direction.

"If something happens don't wait at the front counter, go and knock on doors," he said.

"The more doors you knock on the more information you get."

Lainie Coldwell's body was found at the base of a tree. ( Supplied: Gerry Thornton )

The Coldwell family await an appeal by Mahony to be heard, but said outside court last year his sentencing marks the beginning of a long journey towards healing.

They hope to also reconnect with their granddaughter and niece, who they have had no access to for years.

"We hope that we can now be part of Lainie Coldwell's daughter's life — we have had little contact since her death," Ms Grant said.

A date for the appeal is yet to be set.