The daughter of a medical researcher whose murder has remained a mystery for three decades has issued a heartfelt plea for assistance in capturing her mother's killer to prevent future tragedies. Janet Brown, a 51-year-old mother-of-three, was brutally murdered at her Buckinghamshire residence on April 10, 1995.

Discovered at the base of her staircase, she was naked, gagged, and handcuffed, but detectives ruled out a sexual motive for the crime. Adding to the details that don't add up, despite a thorough search of her home during the break-in, nothing was taken.

Thames Valley Police hold a crucial piece of evidence, a DNA sample from the crime scene believed to belong to the killer, yet it matches no one in their records. Over the course of the past 30 years, investigators have tirelessly screened and ruled out over 1,000 men, but the culprit remains at large.

Zara Harden, Mrs Brown's eldest daughter, expressed her confusion and distress over why their peaceful home and her short, vulnerable mother were targeted. She said: "Ultimately her killer, or killers, have so far gotten away with it."

She added: "We want to see them prosecuted, and not to have somebody who is extremely dangerous still be out there on the loose, who could commit other crimes and against other women or other people.

"We just want to stop it happening again."

On that fateful evening, Mrs Brown, a former midwife turned research professional at Oxford's John Radcliffe Hospital, was by herself at home.

With her older children Zara and Benedict, then aged 22 and 21, away from home, and her youngest daughter Roxanne, 17, out celebrating a friend's driving test success, Mrs Brown was alone when the assailant struck while her husband Dr Grahaem Brown was working in Switzerland.

The killer first attempted to breach the glass of double-glazed patio doors by cutting it before resorting to forcing his way in. Authorities estimate that Mrs Brown met her grim end sometime between the hours of 8.15pm and 10.15pm on that fateful evening.

It wasn't until the next day that a builder and his son, set to work on the property, discovered Mrs Brown's lifeless form.

In her impassioned plea, Ms Harden stated: "Somebody must know something because there would have been a lot of blood."She added: "She was handcuffed and beaten badly, literally bludgeoned to death.

"It doesn't matter if a person didn't come forward at the time. It's not too late."

Peter Beirne, who leads Thames Valley Police's Major Crime Investigation Review Team, said: "I still believe there are people who have information or suspicions about this vicious murder."

"I would urge anyone with names of people they think could be linked to Janet's murder or anyone with information to make contact with the police or Crimestoppers.

"Do you have a friend or loved one who acts strangely when this case is mentioned in the news, or someone who is obsessed with this investigation? Any information whatsoever could help my team to finally solve this murder for Janet's family.

"We have a DNA profile that was left at the scene. It does not belong to the family, and we believe it could be a vital piece of evidence linking the killer to the scene.

"If you have suspicions, it is very easy for our team to trace and request a DNA sample from the person you suspect, or a relative of theirs if they have perhaps passed away or have emigrated."

A reward of £20,000 is available for any information given to Crimestoppers that leads to the arrest and conviction of the murderer.

Anyone with information can reach out to the police online or by dialling 101, quoting reference 695 (4/8); or to stay anonymous contact Crimestoppers on 0800 555111 or online.