A Sydney woman allegedly murdered by her husband was more likely to have had an accelerant poured or thrown on her by someone else than to have burned herself, an expert has told a jury.
"The fact that (Paarwinder) Kaur has no burns to her scalp and upper face would be very unusual if the burns were self-inflicted," burns specialist Professor Peter Maitz testified in the NSW Supreme Court on Thursday.
"In my opinion, it is more likely the accelerant has been poured or thrown over her by others."
Kulwinder Singh, 41, has pleaded not guilty to murdering his 32-year-old wife in early December 2013 at their Rouse Hill home.
The Crown alleges the railway worker was responsible for her death but he told police "she did it to herself" while he was upstairs.
Only Ms Kaur's fingerprints were found on a petrol container and cigarette lighter discovered in their laundry.
Prof Maitz said photos showed Ms Kaur suffered full-thickness burns to 90 per cent of her body, except for the soles of her feet, her scalp and her face.
In his experience, when burns were self-inflicted people poured the accelerant over their heads before lighting it, but Ms Kaur had no burns to her face and head.
"My personal experience, having treated dozens of patients that went through this unfortunate event, is that the vast majority survive and the vast majority have extremely deep burns on their scalp and face, because that's where the liquid ignites first."
Prof Maitz referred to photos taken of Singh's hands 12 hours after the fire, which he said showed partial-thickness burns and blisters on some fingers.
A neighbour has told the jury she saw Ms Kaur covered in flames moving down the driveway while Singh was behind her with his hands outstretched towards the edge of the intense fire.
Another neighbour said she saw Singh patting his wife on the left shoulder as she was engulfed in the fire.
Prof Maitz said 90 per cent of the surface of Singh's palms were uninjured, which suggested they were "not exposed to a heat source" and also suggested one palm was protected "either by him making a fist or holding something".
"If this hand would have been used to try and extinguish something on fire, I would expect a more uniform burn injury, not two to three blisters on the fingers," he said.
Under cross-examination, Prof Maitz agreed the vast majority of suicide-by-burning attempts in Sydney were by people from India, Pakistan or Sri Lanka.
Ms Kaur and Singh married in India in 2005 and came to Australia the next year.
In a filmed walk-through with police - shown to the jury on Thursday - neighbour Michelle Hartmann said she had seen Singh patting his wife who had flames about 60 centimetres long around her as they came down the driveway.
"It was definitely an attempt to get rid of the flames and it did not appear aggressive," she said.
He later told her: "The last month of my life is so s*** - now look, now look", indicating his blistered and burnt hands. The trial continues.