Billie-Jo Jenkins was battered to death with a metal spike at the home of her foster family in Hastings, East Sussex, in February 1997.

The BBC's Emily Watson: "An appeal will be launched based on the new evidence"

Sion Jenkins was found guilty of her murder last July, and was sentenced to life imprisonment.

The 40-year-old has denied his guilt throughout the case, and is appealing his conviction.

And now an investigation for Channel 4's Trial and Error programme says new forensic tets throw doubt on the conviction.

Mist of blood

The prosecution at Lewes Crown Court hinged on forensic evidence, which trial judge Mr Justice Gage called "compelling", of a fine mist of blood on Jenkins' jacket.

Billie-Jo: Case hinged on a mist of her blood

Prosecution experts said the fine droplets must only have come from a fierce spray of blood at the time of the killing, thus proving Jenkins was the murderer.

But at the trial, Jenkins' defence claimed the flecks of blood had got onto his jacket as he cradled his dying foster daughter in his arms.

A prosecution witness said this was impossible, as to produce such a spray Billie-Jo would have had to have been breathing extremely hard.

Yet by Jenkins' own admission, in a 999 call to the police to say that he had found her body, his daughter was not breathing as he held her.

Forensic mistake?

But the programme says new tests by breathing expert Prof David Denison show that Billie-Jo could indeed have inaudibly breathed out the mist, after she was dead.

Billie-Jo was murdered at home

The tests, commissioned by the programme and carried out in his Cambridge laboratory, show that the blood could have come from tiny amounts of air leaving through a "pinhole" in Billie-Jo's nose, which was blocked with blood.

Hundreds of laboratory tests have shown that just an eighth of the amount of air used for a normal quiet breath could have produced such a mist, he says.

The programme says the forensic "evidence" produced at the trial, was in fact a forensic "mistake".

Another murderer

The programme also investigated the possibility that another person committed the murder, and accuses police of not following up leads.

Billie-Jo had told a number of friends that someone was following her, in the weeks before her death.

A series of incidents at an empty property next door had been reported to the police by the Jenkins family.

And on the day Billie-Jo died, there were 35 sightings of a psychiatric patient acting suspiciously in the park next to the Jenkins' house. The man was arrested but police released him several days later.

Vicious temper

Jenkins is due to appeal against his conviction in a seven-day hearing beginning on 29 November.

His lawyers have said that the fresh scientific evidence, and the theory of a second murderer, will be raised during the appeal hearing.

However, the prosecution case also rested on a number of other factors, such as that Jenkins had a vicious temper and had beaten both his wife and Billie-Jo in the past.

At the time of the trial he was also revealed as a liar, who had fabricated qualifications to get his job as a deputy headmaster at a local school.