A murder accused has told a jury he set his mother on fire by accident.

William Kelly, 42, denies murdering 71-year-old Cathy Kelly at their home on Kilmaurs Road in Kilmarnock, East Ayrshire, on February 11, by assaulting her then pouring petrol over her and setting it alight.

Kelly told his defence QC Gordon Jackson that minutes before he had spilled petrol over his trousers and shoes while cleaning a car part in the garage.

He said he went back into the house for a cigarette and found his mother lying on the living room floor.

Kelly claimed: "I sparked the lighter to light the cigarette. Then it was a blue flash."

Mr Jackson asked Kelly: "You are saying your mother was accidentally set on fire?"

The accused replied: "Yes."

Earlier in the trial, the court heard from Kelly's former partner, Eleanor Banks, who claimed Kelly assaulted his mother and then doused her in petrol before setting her on fire.

Kelly said on Tuesday: "No, I didn't do that."

The court heard Kelly suffered injuries to his legs, hands and face in the blaze.

A pathologist earlier told the court Ms Kelly had bruising, and broken ribs and suffered second degree burns to 45% of her body. She also had a cut to her tongue and bruised lips.

Dr Emma Kemp told prosecutor Ashley Edwards QC she had examined Ms Kelly's windpipe and had found no soot there.

Ms Kemp said: "The lack of soot in the airways suggests that Ms Kelly was either dead when the fire started or dead very soon afterwards."

The pathologist added: "It suggests she was dead or deeply comatose at the time the fire occurred."

Ms Edwards asked: "Could that be because of blows to the head minutes before?"

Ms Kemp replied: "Potentially. The post-mortem examination found evidence of blunt force trauma."

The trial continues.