The top worn by a grandmother the night she died in a fire tested positive for petrol, a court heard.

Forensic scientist Shirley Chin was giving evidence at the trial of William Kelly, who denies murdering his mother Cathy Kelly, 71, by pouring petrol over her and setting it alight.

The pensioner was found with extensive burns at her home in Kilmarnock, East Ayrshire, on February 11.

Ms Chin told prosecutor Ashley Edwards QC that she visited the house on Kilmaurs Road on February 12 and 13 with police officers and firefighters.

The forensic scientist said that on her first visit Ms Kelly's body was still at the scene.

She added: "She was lying on a tarpaulin. She was on her back covered with a blanket and a tent had been erected."

The court heard there was a smell of "accelerant" coming from her top.

Ms Chin added: "There was burn damage to her arms and back. There was little damage to her front and her hair was singed."

The jury heard the top was taken to a laboratory for analysis and tested positive for petrol.

The scientist said Kelly's jeans and trainers were analysed and also tested positive for petrol. His white polo shirt tested negative.

Jurors have heard Mrs Kelly, her son and his then partner Eleanor Banks had been out at a 21st birthday party that night.

Mother-of-five Mrs Banks said earlier in evidence that when they returned home Kelly assaulted his mother and then as she lay face-down on the floor poured petrol over her and set it ablaze.

The court has heard Kelly suffered burn injuries to his hands and face in the blaze.

Ms Chin said in her opinion there were two distinct seats of fire in the house but she could not say which was set first.

She added: "I am of the opinion that the fire was started deliberately."

The trial before judge Lady Stacey continues.