The mother-of-two, a prostitute, was shot numerous times in the head and body in the industrial area of Arndell Park, near Blacktown.

Now a decade after her death, Ms Cawthorne's mother has appealed to the public to help police find her daughter's killer and bring closure to the family.

"It's been 10 long years since Sandy was killed," Patricia Roberts said.

"Her two sons, now aged 11 and 14, still wonder who killed their mum."

Ms Cawthorne's body was found by a passing motorist just after midnight on Monday, April 12, 2004.

Even though she had been shot repeatedly, she made it 150 metres before collapsing in the middle of Murtha Street. It is believed the shooter kept firing at her as she tried to flee.

Locals heard between five and seven shots fired one after the other.

The next day police seized an abandoned truck from a property in Riverstone.

The truck was seen in the Arndell Park area shortly before and after Ms Cawthorne's death. The owner had previously reported that it had been stolen and it was eventually returned to the owner.

Police still believe it may be the vehicle Ms Cawthorne's killer or killers used to get away.

An image of the truck has been released as part of Tuesday's renewed appeal.

While police divers also searched a nearby creek in the days following Ms Cawthorne's death, little else was heard until 6½ years later when detectives from Blacktown released an image of a man they wanted to talk to.

The man was Caucasian, in his late 40s or early 50s, 170-185 centimetres tall, with grey hair and a tanned complexion.

However, NSW Police said: "Detectives have followed up numerous lines of inquiry in the 10 years since Ms Cawthorne's murder, but have been unable to find the person or people responsible for her death."

Detective Inspector Con Galea, who has been the officer in charge of the case since Ms Cawthorne's death, urged anyone with information to contact police.

"Sandra's poor mother and her two boys still don't know who killed her or why," he said.

"They've suffered for far too long, and deserve closure."

Detective Inspector Galea said Ms Cawthorne's line of work "exposed her to a lot of dangers" but her death was particularly violent.

"In the four years I worked in Blacktown there were no [other] incidents like this," Detective Inspector Galea said.

"From our exploration of her background, even though the line of work isn't what everybody would do, she was well considered by other girls who worked in the area.

"We've never come across anyone who bad mouthed her, spoken down about her. That's one of the perplexing things about trying to establish a motive. There is nothing clean-cut about why someone would want to kill her.

"We have exhausted all of our inquiries on this case, yet we are certain there are people out there in the community who know the truth," Detective Inspector Galea said.

"We want those people to contact us and remind them that they can do so anonymously.

"We don't need to know who you are, but we do need the information you have regarding Sandra's murder."

Friends said that, at the time of her death, Ms Cawthorne was battling a drug addiction but was trying to clean up her act before the birth of her third child, Fairfax Media has reported.

"The police have done an excellent job but they really need the assistance of the public to help them find my daughter's killer," Ms Roberts said.

"I am pleading with anyone out there who has information that could assist police to please contact Crime Stoppers."

The Crime Stoppers number is 1800 333 000.