A special feature into the murder of Claire Tiltman will be aired on BBC Crimewatch tonight (March 2).
The 16-year-old was stabbed to death in an alleyway off London Road in Greenhithe on January 18 1993.
Her killer, Colin Ash-Smith, 46, was found guilty of her murder 21 years later on December 11 last year following a five-week trial at Inner London Crown Court.
Colin Ash-Smith (left) and tragic Claire Tiltman (right).
He was sentenced to life in prison, bringing an end to one of Kent's largest ever investigations.
Ash-Smith, who is already serving life for attacks on two other women, stabbed Claire to death four days after her birthday and was first questioned as a suspect in 1995.
Claire's parents, Linda and Cliff, were convinced he was the killer but they died before he was charged with her murder.
The alleyway in Greenhithe where Claire Tiltman was stabbed to death
The Crimewatch feature, called How They Caught Claire Tiltman's Murderer will include interviews with the teenagers friends and detectives involved in the investigation.
Lawyers acting on Ash-Smith's behalf have now confirmed they will appeal against the conviction.
How They Caught Claire Tiltman's Murderer will be shown on Crimewatch on BBC1 at 9pm tonight (March 2).
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