A schoolboy may have rolled around in mud in an attempt to put out flames that were burning his body, a court heard yesterday.

Forensic scientist Ruth Ramage said 15-year-old Kriss Donald was still alive when his body was engulfed by fire.

The scarred, semi-clothed body of the teenager, from the Pollokshields area of Glasgow, was found on the city's Clyde Walkway on March 16, 2004, the day after he was allegedly abducted.

Imran Shahid, 29, his brother Zeeshan Shahid, also 29, and Mohammed Faisal Mushtaq, 27, are on trial at the High Court in Edinburgh, where they deny racially aggravated murder.

They are accused of abducting Kriss from Kenmure Street, Pollokshields, repeatedly stabbing him and setting him on fire.

Ms Ramage, 42, who works with Strathclyde Police, told the court she was brought in to help with the murder inquiry and was sent to the scene of the body find.

The scientist said she found pools of blood, a smell of petrol and scorch marks to logs near the spot where the burnt, partially-clothed body lay.

The trial heard there was reddening and skin damage to parts of the deceased's body.

There also appeared to be stab wounds to the back.

The jury of six men and nine women heard soil or mud staining appeared to cover some of the burns and there was burnt debris lying between the logs and the place where the body was found.

Advocate depute Mark Stewart QC, for the Crown, asked the witness about the significance of those findings.

Ms Ramage replied: "In my opinion he was still alive when he was burning."

There had been a lot of rain at that time and the deceased might have attempted to put out the flames while he was on fire, the witness added.

"He may have tried to extinguish the flames by rolling in the mud," she told the court.

The hearing continues.