Kriss Donald was found with stab wounds and 70% burn wounds

Dr Marjorie Black said it was likely the schoolboy had been restrained as he was stabbed. She also found burns covering 70% of his body.

The 15-year-old's body was found on the Clyde walkway on 16 March, 2004.

Mohammed Faisal Mushtaq, 27, Zeeshan Shahid, 28, and brother Imran Shahid 29, deny racially motivated murder.

Dr Black, 44, of the University of Glasgow, said Kriss bled very heavily and some of the knife wounds pierced his internal organs.

In most victims who have received 12 or 13 stab wounds you would expect there to be defensive injuries Dr Marjorie Black

She carried out an inspection of Kriss's injuries at the scene and during a post-mortem examination.

Jurors were shown a diagram outlining the 13 different stab wounds suffered by the schoolboy.

There were seven cuts to his front, mostly in the area of the lower chest and abdomen, five cuts on his back and one to his left arm.

The arm injury could be characteristic of a defensive injury commonly sustained by victims trying to shield themselves from blows, the court heard.

'Unconscious or restrained'

During questioning by advocate-depute Mark Stewart QC, Dr Black said that the presence of only one defensive injury could reveal how many people were involved in the attack.

She said: "In most victims who have received 12 or 13 stab wounds you would expect there to be defensive injuries.

Dr Black examined Kriss's body on the Clyde walkway

"The absence of them would suggest that he's been unable to defend himself and there are two possible scenarios for that - one being that the victim was unconscious, the other being that he is restrained in some way and unable to defend himself."

She said there was no evidence that the victim was unconscious.

She added: "This leads me to the most likely scenario that he is being restrained by one or more people while he's being stabbed."

Dr Black told the court that some of the wounds had pierced the rib cage, arteries and internal organs such as the lung, stomach and intestines.

She said the knife wounds could have been made by one or more assailants and one or more weapons.

The Crown has reached the end of its case