Vicky Hamilton's body was identified through dental records
Schoolgirl Vicky Hamilton may have been strangled, a murder trial has heard.
Pathologist Dr David Rouse told the High Court in Dundee compression of the neck was a possible cause of death.
However, he said it was not possible to be certain how she died and under cross-examination admitted that fright or natural causes could be to blame .
Peter Tobin denies the abduction and murder of the 15-year-old in Bathgate in 1991 and has lodged a special defence of alibi.
'Extent of decomposition'
Vicky was last seen in Bathgate, West Lothian, on 10 February 1991 as she made her way home to Redding, near Falkirk.
Dr Rouse performed a post-mortem examination on Vicky's body after it was dug from the garden of a house in Margate, Kent, last year.
Vicky, who had been cut in two, was identified by her dental records, the trial heard.
Dr Rouse, a forensic pathologist for 20 years, said: "There are no obvious signs of major blunt or sharp penetrating injury. Apparent bruising of the neck over the front of the spine may indicate death from neck compression.
"However, the extent of decomposition prevents precise determination of the cause of death."
During cross-examination, defence QC Donald Findlay put forward possible alternative scenarios to strangulation and asked Dr Rouse to comment.
Dr Rouse admitted that it was possible that Vicky could have died of fright or natural causes.
Mr Findlay said: "The reality is that from what information we have at this point in time we are never going to specifically know what caused the death."
The court heard the grave had been professionally dug
However, Solicitor general Frank Mulholland QC, prosecuting, challenged the idea that a healthy 15-year-old girl on her way home to see her mother would simply drop dead.
He asked the doctor: "If someone died of natural causes, would you expect, possibly, anyone in the vicinity of that person to maybe contact a doctor, an ambulance or undertaker or something?"
Dr Rouse told him: "That is the usual procedure."
The trial also heard that Mr Tobin had experience of digging trenches.
Simon Nottle, 53, said he had worked for Brighton Water Department between 1973 and 1977 and Mr Tobin had been part of the same maintenance and repair gang.
Mr Nottle pointed out Mr Tobin in court.
"We all did the same work, we all dug together," he said.
The court also heard that the grave in the back garden of 50 Irvine Drive, Margate, where Mr Tobin used to live, had been professionally dug.
Peter Roles, 64, of the Construction Industry Training Board, was shown photos of the hole.
"This is the sort of excavation we teach people to do," he said.
Mr Roles added that a layer of concrete found during the excavation would prevent the ground sinking if something underneath were to decompose.
Mr Tobin is accused of abducting Vicky and taking her to Robertson Avenue in Bathgate, West Lothian, on 10 February, 1991, which the Crown alleges was then occupied by him.
The charge also alleges that there or elsewhere he drugged her, struggled with her, compressed her neck, indecently assaulted her and murdered her.
He is also accused of attempting to defeat the ends of justice.
It is alleged that he concealed Vicky's body and removed and disposed of a number of items of her clothing and footwear.
He is also accused of cutting her body in two and wrapping it in coverings and bin bags.
Then, allegedly aware that police were conducting a missing person's inquiry, Mr Tobin is said to have put Vicky's purse under a portable cabin to mislead police into believing she had run away from home.
Mr Tobin denies all the charges against him and has lodged a special defence of alibi, saying that between 1700 GMT and midnight on 10 February, 1991, he was in the Portsmouth area and was thereafter travelling to Scotland, arriving in Edinburgh at 0630 GMT the following day.
The trial, before Lord Emslie, continues.