Deidre Maree Kennedy was not yet 18 months old when her small, lifeless body was found atop the roof of a public toilet block in a Queensland park in 1973.

The toddler had been snatched from her bed in the dark of night, before she was strangled, bitten, sexually assaulted and left for dead on the roof of the toilet block in Limestone Park, Ipswich.

It is remembered as one of the most heinous crimes to rock the northern state.

It is also the crime that came to define the nine-year policing career of federal MP Peter Dutton, long before he was in the race for the nation's top job.

The saga of the campaign to seek justice for the baby's family provides an insight into the single-mindedness with which Mr Dutton will pursue a goal once he has locked onto it.

Mr Dutton, who joined the Queensland police force 1990 at 18, worked as a young detective on Deidre's murder, for which the same man has been found guilty and acquitted twice.

In 1985 Raymond John Carroll, a former RAAF recruit, was convicted of the murder of Deidre and sentenced to life in prison, however he was later acquitted in the Court of Criminal Appeal.

When new evidence arose in 1990 linking Carroll to the crime, he could not be charged again.

In 2000, he was then tried for perjury, for lying in the original case, and found guilty. However this too was overturned on appeal, partly because it breached double jeopardy.

Carroll maintains his innocence.

The case became the catalyst for a movement to change Queensland's double jeopardy law, prompting a lengthy campaign led by Mr Dutton and Deidre's mother Faye Kennedy.

On the 30th anniversary of the toddler's death, the two launched a petition calling for the law to be changed under their proposed model dubbed "Deidre's Law".

In 2006 Mr Dutton accompanied Ms Kennedy on a road trip from Cairns to the Gold Coast to gather more than 100,000 signatures to present to then-Queensland premier Peter Beattie.

Changes to Queensland's double jeopardy legislation were finally passed in October 2007. While the changes allowed for an acquitted person to be retried if new evidence came to light, in Queensland the law only applied to crimes committed after 2007.

In 2014, then Queensland attorney-general Jarrod Bleijie made changes to allow someone to be tried for the same crime, regardless of when it was acquitted.

A source close to the Kennedy family told Fairfax Media they held Mr Dutton "in the highest esteem" for his commitment to their campaign, describing him as "the driving force" behind it.

Mr Dutton's black-and-white view of the world, reinforced during his time in police ranks, was highlighted in his maiden speech to Federal Parliament in 2002.

"I often say to people that, as a police officer, I have seen the best and worst that society has to offer," he said.

"I have seen the wonderful, kind nature of people willing to offer any assistance to those in their worst hour, and I have seen the sickening behaviour displayed by people, who, frankly, barely justify their existence in our sometimes over-tolerant society."

Dan Purdie, who worked alongside Mr Dutton as a young constable at Brisbane's central city station, told Fairfax Media last year that Mr Dutton coupled a passion for "law and order" with "an unbelievable capacity for work".

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When contacted this week Mr Purdie declined to offer further comment. Another former officer, who had worked alongside Mr Dutton, said he had been asked to remain in the background at this stage of Mr Dutton's leadership bid.

Queensland's double jeopardy provisions were enacted for the first time last month, when a man was arrested in relation to a murder in the 1980s.

A police spokesperson confirmed an application would be made to the court for an acquitted person to be retried for the offence.