Pregnant with her seventh child, Elizabeth Henry was beaten and partially burnt before her body was discovered outside Brisbane in 1998.
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More than 25 years later, Queensland Police have offered a $500,000 reward for information to help solve the 30-year-old's murder.
Her heartbroken family issued an emotional plea for help on Tuesday.
"We are unwavering in our hope that there will be justice for Liz," her sister Jennifer Schefe told reporters.
"I believe that there are individuals who possess crucial information that can aid in solving the case.
"It's not something that should be taken to anyone's grave."
Ms Henry was a sex worker last seen in Brisbane's Fortitude Valley before midnight on February 11, 1998.
Hours later her body was discovered by a jogger on a roadside gravel reserve at Samford 25km away.
Ms Henry was four months pregnant.
Police said she had been violently assaulted with a blunt, heavy object and was found with major head injuries.
The clothes Ms Henry had been wearing and the handbag she had at the time have never been recovered.
Investigations indicated Ms Henry was killed at another location and moved to the gravel area before an attempt was made to burn her body.
Her parents had passed away without answers, Detective Acting Senior Sergeant Anthony Johns said.
Ms Henry's six children grew up without their mother, and she would be a grandmother of six if still alive.
"Her parents lost their daughter, her siblings lost their sister, and her children have never had the opportunity to know her," Ms Henry's daughter Grace said on Tuesday.
"We as children had to learn how to mother and father ourselves, we didn't have a mother to call when life was hard ... I live the loss of her every day."
Police said neither a weapon nor the initial site where Ms Henry was killed have ever been identified.
But Det Sgt Johns was confident the murder would be solved, saying Queensland's homicide cold case team has reviewed the case and discovered further information, without revealing any detail.
"We do believe with public assistance, irrespective of the passage of time, this crime can be solved, offenders can be brought to justice and we can provide some answers to those family and friends," he said.
Australian Associated Press
