Traces of DNA found on the body of a 15-year-old schoolgirl belong to the man accused of her murder, a court has been told.

Jurors at the High Court in Dundee also learnt that the chance that DNA found on a knife in the former home of Peter Tobin, 62, came from someone other than Vicky Hamilton, of Redding, Falkirk, was more than a billion to one. The evidence also suggested that Vicky could have been sexually violated, as partial profiles of Mr Tobin’s DNA were found on swabs taken from her body during a postmortem examination.

Mr Tobin, 62, denies abducting and murdering Vicky and burying her body parts. He further denies sexually assaulting her and has lodged a special defence of alibi, saying that he was hundreds of miles away in the South of England when she was abducted on February 10, 1991. Earlier in the trial the court heard evidence that Vicky’s body was found in a shallow grave in the back garden of Mr Tobin’s house in Margate, Kent, after he had moved from West Lothian in 1991.

Nicola Clayson, 39, a forensic scientist, said that the probability was more than one in a billion that the DNA on the knife found in Mr Tobin’s former home in Bathgate came from someone other than, and unrelated to, Vicky. She also told the court that partial DNA profiles were obtained from two intimate swabs of Vicky’s remains. An internal swab matched 7 out of 20 numbers of Mr Tobin’s DNA profile, which meant that a probability of it coming from someone other than Mr Tobin was 1 in 34,000. An external swab matched 4 out of 20 DNA numbers, which represented a probability of 1 in 114 that it came from someone other than, and unrelated to, Mr Tobin.

Asked by Frank Mulholland, QC, Solicitor-General, prosecuting, about the source of the DNA, Ms Clayson said: “It’s most likely to have originated from semen.” Challenged by Donald Findlay, the defence QC, she said that a positive result had not been produced because the bodily fluid would have degraded. “The DNA profile that we obtained cannot be specifically assigned with 100 per cent certainty to any particular body fluid,” she said. Mr Findlay said that a probability of 1 in 114 could mean that the profile could be obtained from 428,571 people in Scotland.

The court had previously heard that a small piece of tissue was found on a knife taken from 11 Robertson Avenue, Bathgate, in June last year. Ms Clayson said yesterday that an almost complete DNA match was obtained from the knife in 19 out of 20 areas for comparison.

The trial has also heard that DNA found on Vicky’s purse matched that of Mr Tobin’s son, Daniel, who was a toddler when Vicky disappeared on her way to her home. Mr Findlay challenged the statistics applied to DNA tests as “gobbledygook” and said the presence of Daniel’s DNA did not prove he had actually touched it.

The court also heard extracts from a police interview on July 21, 2007. Mr Tobin was shown a photograph of Vicky and said he did not know her. He denied having met Vicky and denied any knowledge or involvement in her disappearance. Mr Tobin said that he had “kicked out” his former wife and she had gone to the South of England, and he looked after his little boy at weekends. Police asked him: “Can you try and remember where you were on February 10?” Mr Tobin replied: “Just back and forward, but if it was the weekend I would have the wean with me anyway.”

Mr Tobin is accused of abducting the schoolgirl, drugging her, causing an injury to her neck, committing a sexual assault and murdering her. It is alleged that he cut her in two, wrapped her body parts in bin bags and buried them.

The trial continues.

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