Both women were sexually assaulted, battered and strangled
Police investigating the 1987 murders of two women in Kent have said more than 500 people have been eliminated from their inquiry through DNA samples.
Wendy Knell, 26, was found dead in a bedsit in Guildford Road, Tunbridge Wells, in June 1987.
Six months later Caroline Pierce, 20, was attacked outside her bedsit in the town. Her body was later discovered in a dyke on Romney Marsh.
Kent Police believe they have the full DNA profile of the suspected killer.
Officers have been visiting people of interest to the inquiry and with their consent obtaining samples of their DNA for comparison to that found at the crime scene.
Bill and Pam Knell have expressed hope that their daughter's killer will be found.
"I am very pleased it [the inquiry] is still going on, so we are still hoping," Mr Knell said.
"We just wait for the phone call."
Mrs Knell added: "I'd like to know who it was before I die."
Officers believe one person was responsible for both murders.
Both women, who had jobs in Camden Road in Tunbridge Wells, had been sexually assaulted, battered and strangled.
Police said there were no "clear signs" of forced entry to Ms Knell's flat in Guildford Road after the murder on 23 July 1987, but her key ring and diary were missing.
Officers also believe a footprint on a blouse at her home, that may have come from a rare Clarks' trainer, belongs to the killer.
A 19-year-old neighbour of Ms Knell was warned by a stranger not to leave their windows unlocked a few days before her murder. Police have issued an e-fit of the man.
Ms Pierce was wearing a long black skirt and red jumper when she was last seen in Grosvenor Park on 24 November 1987.
Her body was found by a farm worker 40 miles away in a field near St Mary in the Marsh on Romney Marsh on 15 December.
Detectives said a set of Ms Pierce's keys was also taken.
The head of Kent Police's cold case investigation team, Det Ch Insp Dave Withers, said: "The investigation into the murders of Caroline Pierce and Wendy Knell have never been closed.
"The cases have been regularly reviewed as new information comes to the police or new forensic opportunities become available."
Bill Knell appealed for anyone with information which would help find his daughter's killer to come forward