knife found near the scene could have been used in the crime.

Dr. James Johnston said that a serrated weapon found in the water at the swing bridge, near the Ferry Reach site where Miss Middleton's mutilated body was found, was unlikely to have been involved in her death.

Speaking during day seven of the murder trial of Justis Smith, he said he was shown the knife days after the murder and asked if he thought it was used by the killer.

"At the time I felt it was unlikely because I wasn't expecting a steak knife,'' he said. "I was concerned about the serration on the blade, angle, crustaceans and rust on the blade, which indicated it had been in the water for some time.'' But later the King Edward VII Memorial Hospital consultant admitted: "I have never seen injuries caused by a knife such as the serrated one found in the water.'' Dr. Johnston was called to Ferry Reach on July 3, 1996, after the body of Rebecca Middleton, 17, was discovered lying in the road in the early hours of the morning.

She had been sexually assaulted, stabbed and tortured during the attack, which the Crown allege was committed by more than one person.

They claim the Canadian holidaymaker died after accepting a lift on a motorcycle from Justis Smith and Kirk Mundy.

Justis Smith, 19, of Deepdale Road East, Pembroke, pleads not guilty to premeditated murder.

Kirk Mundy was sentenced to five years imprisonment after pleading guilty to being an accessory after the fact.

Giving evidence in chief to Solicitor General William Pearce QC, for the Crown, Dr. Johnston detailed the autopsy and its findings.

He said there had been a blunt blow to the side of her head and a slap to her face, but she would not have been unconscious.

There were six slashes across her throat, of varying depth, which had been made under control. Another cut had opened the jugular vein.

Bruising associated with a sexual assault was also evident, along with numerous other cuts and slashes.

Of the 16 stab wounds, he concluded there were three fatal ones, in the neck, chest and abdomen. The loss of blood from them, combined with shock from the attack, caused death.

Mr. Pearce questioned him on experiments that took place on Miss Middleton's clothing with knives, including one believed to the murder weapon.

But John Perry QC, representing Smith, said Dr. Johnston's opinions were "valueless''.

Under cross examination, Dr. Johnston said it was possible the assailant was behind the victim.

And he concurred that the width of the wounds would be consistent with the width of the knife blade -- and that many of the cuts were smaller than the knife found in the water.

Doctor casts doubt on knife Under re-examination from the Solicitor General, Dr. Johnston said stab wounds are often smaller than the width of the weapon, because of the elasticity of the skin.

Earlier in the day, John Perry told forensic expert Dr. Michael Baden that his version of the events that led to Rebecca Middleton's death were different to many other witnesses in the case.

He questioned his stance with regard to the position of the victim when she was stabbed, the attacker and how many people could have been involved in the crime.

The stab wounds could have been made whilst she was held by her hair by one person, behind her, he claimed.

And the dirt on her knees, shins, feet and hands showed that she was kneeling at some point.

"You are disagreeing with a lot of people,'' said Mr. Perry.

Dr. Baden replied: "I came here to give my opinion, I did not try to tailor my opinion to other people's.'' He agreed that she may have been kneeling at some point but said it was impossible to tell if the stab wounds came from the front or rear.

He said there were disagreements on some minor points but said it was clear that the 17-year-old was viciously murdered and that two people were involved.

And he concluded in re-examination by Solicitor General William Pearce QC, that she was in a seated position and was stabbed repeatedly to get her to cooperate.

The trial continues today.