A son has pleaded for help to solve his mother’s 1997 murder, as a £10,000 reward is offered.
Patricia Grainger, 25, was strangled, stabbed and sexually assaulted near her home in Parson Cross, Sheffield, in August that year.
Her body was dumped in a brook in nearby woodland and her killer has never been found.
Her son, Danny Grainger, said: “Someone out there knows what happened to Pat. No more secrets.”
Her family has put up £5,000, matched by Crimestoppers, for a reward for information leading to the conviction of the person or people responsible for Mrs Grainger’s murder.
Mr Grainger also set up a website in an attempt to find her killer.
Mr Grainger, said: “No-one should be able to get away with such a terrible crime on an innocent young mum.
“My vulnerable mum was treated in the most sickening way possible, used and abused as if she wasn’t human.
“She had learning disabilities and that made her trusting of anyone who showed her interest. They abused that trust.”
Ms Grainger was living with her son and her parents when she was murdered and dumped at Hartley Brook Dike, near houses on Deerlands Avenue on the Parson Cross estate.
Her body was submerged face down in the water by the weight of a divan bed base.
Mr Grainger urged anyone with information to contact Crimestoppers.
Gemma Gibbs, of the charity, said: “Whilst many years have passed, her son and family deserve to see justice done and to have some answers.”
Ms Grainger’s death remains under “continual review”, South Yorkshire Police said.