It was 1993, a month before Christmas, when police prised open the boot of a red Holden Calais in the city's north-west after residents complained about a vile smell in the area.

The body of Graham Bourke, a 44-year-old butcher by trade, was found inside.

He had been shot once in the back of the head and his throat was cut. His large frame was squeezed in the boot of his own car and left to rot about one kilometre from his Hornsby home.

Also in the boot, police found a wrist watch.

Strangely the watch didn't appear to belong to Mr Bourke with a relative telling an inquest in 1994 that she didn't recognise it.

Twenty three years on police are re-examining the watch, with one focus on a hair caught in the wrist band, in the hope it may lead them to a breakthrough.

It is among multiple items, including Mr Bourke's clothing, being looked at again with the help of new technologies.

"It is physical evidence from the crime scene," Unsolved Homicide Unit Detective Chief Inspector John Lehman said.

"It's obviously an opportunity that presents itself that wasn't available back in 1993 and that is based on new forensic technologies that are available to us and we will pursue that."

Mr Bourke's daughter, Lee, was just 10 years old at the time of her father's murder. She has been in limbo ever since, not knowing why anyone would want to end her father's life.

On Wednesday morning, Lee joined NSW Police and NSW Police Minister Troy Grant to announce a $100,000 reward for information leading to the arrest and conviction for the person or people responsible for Mr Bourke's death.

Mr Bourke had been reported missing by his former partner, who knew something was wrong when he did not arrive to pick up their daughter for his regular weekend visit.

Mr Bourke doted on his daughter, and never missed a weekend with her, Marie said at the time.

His daughter Lee, now 33-years-old, says a day doesn't go by without her thinking about her father and if she makes him proud.

"I was daddy's little girl," she told reporters on Wednesday.

"I used to go motorbike riding with him all the time, gardening ... whenever he was home I was with him."

Lee said the arrest of the person responsible for her father's murder would bring closure but more importantly her family want to know why he was killed.

Police traced Mr Bourke's last movements to a butcher's shop in Pittwater Road, Mona Vale, on October 25, 1993. Mr Bourke had previously worked for several years at the shop. He first stopped in at the newsagent next door to buy a lottery ticket, before popping in to the butcher shop for a brief chat with friends.

He left the shop about 6.45pm, saying he was going directly to see a man who owed him $5000, a coronial inquest into Mr Bourke's death heard in 1994.

At the inquest, police raised concerns that the person Mr Bourke was meant to go and see, a man named Geoffrey Smith, was "in possession of further knowledge in relation to his matter".

However Mr Smith strenuously denied a meeting took place that night in 1993.

It is understood Mr Smith, who briefly employed Mr Bourke at his Mona Vale butcher, is now living in Western Australia.

The coroner returned an open finding, that Mr Bourke had been "killed by person or persons unknown".

Inspector Lehman said Mr Bourke didn't have any enemies that police knew of and labelled his demise brutal and vicious.

"To be dumped like that in the boot of his own car and left like that for five weeks in a street is quite horrific and quite callous and shows the brutal nature of this crime," he said.

Strike Force Dalgetty has been formed to investigate Mr Bourke's death, and anyone with information has been urged to contact Crime Stoppers on 1800 333 000.

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