As Kathy Marks reports, a massive DNA testing programme helped to trap Louise Smith's killer.
The one small comfort for Louise Smith's parents yesterday was that David Frost, 22, pleaded guilty at the last minute, sparing them the ordeal of sitting through a two-week trial.
Frost, a civil engineering student at the University of Surrey, changed his plea, admitting that he murdered 18-year-old Louise, a clerical worker, and dumped her naked body in a quarry near her home, in Chipping Sodbury, near Bristol.
Her body lay undiscovered for seven weeks, despite the efforts of a volunteer army of 10,000 people, including friends and neighbours of the family, who joined police for the search.
The grim find was eventually made by two 13-year-old boys, who were throwing stones into the disused quarry.
At Bristol Crown Court yesterday, with Louise's parents and brother, Richard, in the public gallery, the judge, Mr Justice Bell, told Frost: "It was an evil thing that you did in the early hours of Christmas Day two years ago, taking the life of Louise Smith. There is only one sentence for murder and that is life imprisonment."
Frost, of nearby Yate, who was described by police as "a very intelligent, clean-cut young man", denied a further charge of rape. The plea was accepted by the prosecution.
After sentence was passed, Louise's parents, Gillian and Robert, called for the return of the death penalty.
Mr Smith said: "People who are opposed to the death penalty should have seen our household over the last two years and the misery that David Frost has caused."
Louise, described as an intelligent, bubbly girl, had spent the evening with friends at Spirals nightclub in Yate shopping centre. A security camera caught her leaving the club just after 2am.
After going to a nearby hamburger bar, she declined two offers of a lift home, as she lived only a 10-minute walk away. She was said to have been looking forward to a traditional Christmas Day with her family.
The court was told that Frost was also captured on camera. After drinking heavily in a public house, he turned up at the nightclub just before 1am, but failed to gain admission.
In interviews with police, Frost said that he approached Louise on her way home and persuaded her to walk with him to the Barnhill Quarry, where he took her clothes off and had sex with her.
Afterwards, he said, she began to get upset. "She was crying louder and louder, and I tried to calm her down, reasoning with her," he told detectives. Then I put my hand on her mouth and tried to stop her screaming. She went silent."
Frost said that he panicked and dragged her body to the edge of the 200ft deep quarry, which he knew well because he had played there as a child. Louise was wearing only her shoes when she was found. Her clothes, jewellery and handbag were scattered around the area.
Police visited 10,500 homes during the investigation and also interviewed more than 14,800 people. DNA tests were carried out on 4,500 men. A sample was also requested from Frost, who had been staying at his parents' house for the Christmas holidays. He agreed, but did not turn up to an appointment, and then left for South Africa to take up a job with an engineering company.
Officers contacted him there and mouths swabs were eventually taken, which resulted in a close DNA match. Police travelled to South Africa to interview him, and he then returned to Britain, where he was arrested.