Police have named killer Levi Bellfield as a key suspect in the unsolved murder of Surrey teenager Milly Dowler.
He was linked to her killing after his conviction at the Old Bailey of the murders of two young female students and the attempted murder of a third.
Milly's body was discovered on Yateley Heath, Hampshire, six months after she disappeared on the way home from school in Walton-on-Thames, in March 2002.
Her parents say they will not rest until her killer is brought to justice.
Plea for information
It has emerged that Bellfield was arrested and interviewed over her death three years ago.
Officers believe they have compelling circumstantial evidence linking him to the murder. And they have launched an appeal for information on a car seen in the area where Milly disappeared.
Milly's parents, Bob and Sally Dowler, appealed to anyone with information about what happened to their daughter to "find it in your heart" to tell police.
Mr Dowler said: "Imagine not knowing how your daughter died or where or when or by whose hand. Imagine how we as a family live.
"If you know anything that could help answer these questions please find it in your heart to let us know."
"We are pleading for anyone who knows anything to have the courage to speak up," Mr and Mrs Dowler told a news conference.
"Nothing will ever bring Milly back, but even six years on you can still help start easing our pain by letting us know, finally, what happened on our daughter's final days."
Surrey Police are hoping Bellfield's conviction will encourage people who were previously too afraid to speak out to come forward.
Surrey Police and Crimestoppers are providing a £50,000 reward for information leading to Milly's killer.
Det Ch Insp Maria Woodall, who is leading the investigation said: "It may well have been that people have been afraid in the past to come forward and speak to us.
"They may have been protecting someone they no longer feel any loyalty towards."
Detectives involved in Bellfield's trial described him as a controlling womaniser who frequently used his burly physical frame to bully his girlfriends into submission.
Officers are expected to re-interview the former bodybuilder in the coming days.
Car crush theory
They have re-launched an appeal for help in tracing a red Daewoo Nexia seen in Walton-on-Thames on 21 March 2002, the day Milly went missing.
A car of the same model and colour was owned by Bellfield's then-girlfriend, Emma Mills, it has emerged.
Detectives have released a vehicle registration, N503 GLT, and chassis number, KLATF68V1SB554108, and believe it may have been crushed or "recycled" into other cars.
When he was questioned, Bellfield, who ran a wheel-clamping business, failed to account for his whereabouts on 21 March.
At the time of Milly's disappearance Bellfield's then girlfriend had a flat in Collingwood Place, Walton-on-Thames, less than 100 yards from the railway station where the last CCTV sighting of Milly was made.
CCTV cameras further along on Station Avenue captured images of a red Daewoo Nexia, similar to one used by Bellfield.
BBC News crime reporter Ben Ando says Surrey Police do not believe the trail has gone cold and they are still determined to track down Milly's killer.
He says detectives believe they have about three-quarters of a case - what they are missing is that vital extra piece to complete the jigsaw.
This could be to do with Milly's possessions, which have never been found, or the missing vehicle.
But police acknowledge the method of Milly's murder differs significantly from those of Marsha McDonnell and Amelie Delagrange, who were killed with blunt instruments.
Milly was abducted, and her remains found 30 miles away. Those remains did not reveal any injuries, inconsistent with the explosive violence shown in the hammer attacks.
None of her clothing or possessions were recovered - police are still trying to trace her Heathside school jacket, Nokia mobile phone and white purse with an ace of hearts logo on it.
A Surrey Police source said: "We have not given up on Milly.
"We have to keep plugging away until we get the break we want and the family get the justice they deserve."
MILLY DOWLER'S LAST MOMENTS
21 March 2002
1540 Gets off train from her school in Weybridge to meet friends in nearby cafe
1545 Phones her father to say she's about to walk home
1608 School friend waiting at bus stop sees Milly walking up Station Avenue - the last reported sighting
1638 Red Daewoo car identical to one owned by Bellfield's girlfriend at the time caught on CCTV in Station Avenue
18 September 2002
Milly's body found in woods at Yateley Heath, Hampshire