Schoolgirl killer Colin Ash-Smith is expected to formally apply to appeal against his conviction this week.

The former milkman from Swanscombe was found guilty of what was described as the "brutal and premeditated" murder of 16-year-old Claire Tiltman last month.

The teenager was stabbed to death in a frenzied knife attack in an alleyway off London Road, Greenhithe, almost 22 years ago on January 18, 1993.

Knife-obsessed loner Ash-Smith, 46, denied killing the Dartford Grammar School pupil but was convicted by a jury at Inner London Crown Court after a five-week trial.

Lawyers acting on his behalf confirmed today they will be appealing and have until Wednesday to lodge legal documents with the Criminal Appeal Office.

The application will then go before a judge and, if permission is granted, a hearing will be heard at a later date at the Court of Appeal in London.

Applications to appeal must be made within 28 days of conviction.

Ash-Smith, who was branded "pure evil" by cops, was unanimously found guilty of Claire's murder on December 11. He was jailed for life and will spend a minimum term of 21 years behind bars before becoming eligible for parole.

He was already serving a life sentence for two near-fatal knife attacks on women in Swanscombe in 1988 and in Greenhithe in 1995, and it was only after his arrest for the later stabbing that he was first questioned as a suspect in Claire's death.

Claire, who was the only child of Lin and Cliff Tiltman and lived in Woodward Terrace, Horns Cross, near Stone, was viciously attacked just four days after her birthday and as she walked to a friend's house in nearby Greenhithe.

She was stabbed nine times before collapsing on the pavement and dying despite desperate attempts by passers-by and paramedics to save her.

The Tiltman and Ash-Smith families knew each other through membership of the Greenhithe and Swanscombe Royal British Legion Club, and the court heard Ash-Smith attended Claire's funeral wearing the same jacket he wore on the evening he murdered her.

The hunt for her killer was one of the biggest murder investigations in Kent Police's history and remained unsolved until Ash-Smith was charged in February last year after a cold case review by the Kent and Essex Major Crime Directorate.

Crucial in proving his guilt was the discovery by officers of a conversation in which Ash-Smith told a fellow inmate that he had spotted someone on a zebra crossing before he "snapped and attacked" them, as well as a change in law which enabled juries to hear defendant's previous convictions or "bad character".

This included evidence of hand-written notes in which Ash-Smith described the 1988 attack as his "masterpiece", detailed other planned but aborted attacks on women, and once wrote he would "kill a schoolgirl" because it sounded "impressive".

However, Ash-Smith maintained his innocence of Claire's murder, even telling the jury when he gave evidence that despite being "an animal" who habitually carried knives, he had "subdued" his negative feelings towards women between 1988 and 1995.

His defence team also sugested that the jury should consider two other men as "realistic possibilties" for being the teenager's murderer - convicted killer Robert Napper and Dartford man Peter Rivers.

Napper ferociously stabbed Rachel Nickell 49 times on Wimbledon Common in July 1992, before butchering Samantha Bisset in her south east London home in November 1993, as well as suffocating and sexually assaulting her four-year-old daughter.

BT engineer Peter Rivers, 44, stabbed his mother to death before setting himself on fire in February 1994.

An inquest into their deaths later heard that police found a suicide note at the home they shared in Wellcome Avenue in which Mr Rivers wrote: "Mum was beginning to suspect me of killing Claire."

However, Detective Superintendent Rob Vinson, senior investigating officer in the cold case review, said there was no evidence linking Napper, and that Mr Rivers' background had also been thoroughly investigated and nothing found.