The three cuts found on a woman who died in a fire at her husband's law firm could have been caused by the edge of a padlock, an Australian forensic pathologist testified yesterday.

Govindasamy Nallaiah, who is on trial in the High Court for the alleged murder of Madam Low Foong Meng, has maintained that he had used only a bicycle chain and padlock to hit her in a fit of rage.

He was a client of Madam Low's lawyer husband, Mr Rengarajoo Rengasamy Balasamy, and was involved in a dispute over legal fees with him. Govindasamy visited Mr Rengarajoo's office in the Afro Asia Building in Robinson Road on Aug 10, 2011 and had his run-in with Madam Low.

The 70-year-old claims he did not use any other weapon on Madam Low, who was 56. As she lay unconscious on the floor, he set fire to his case file and fled when the fire alarm rang.

The cuts on her body were later documented by Health Sciences Authority's forensic pathologist Gilbert Lau, who testified that they must have been caused by a sharp cutting object such as a knife or cleaver.

The tip of Madam Low's left middle finger was nearly sliced off, while another injury on her left elbow fractured the tip of the elbow. There was a cut on the area between her left armpit and back.

Taking the stand as a defence witness on the eighth day of the trial, Dr Johan Duflou yesterday said a padlock similar to the one Govindasamy told police he used had sharp edges, in his view. And a heavy object with sharp edges can cause a wound with clean edges, he said.

Dr Duflou said he initially thought such a padlock could "likely" have caused the finger injury, and it was "reasonably possible" for the elbow injury to have been caused by it.

But he thought it was "possible but unlikely" for the armpit injury to have been caused by the object.

Dr Duflou, who is a University of Sydney clinical professor and formerly the clinical director of the Sydney department of forensic medicine, said he then performed an experiment to see if such a padlock could inflict a cut similar to the one found on Madam Low's armpit.

He secured pieces of fresh pig skin to a piece of masonry board, and stuck them with the padlock several times. He was able to obtain a similar cut, and changed his view to there being a "reasonable possibility and not unlikely" for a padlock to have caused the cut.

Dr Duflou yesterday also said he was of the view that Madam Low's five skull fractures could have been caused by three blows to the head.

Both Dr Lau and Dr Duflou concluded, based on the amount of soot in Madam Low's airways and lungs, and the level of carbon monoxide in her blood, that her cause of death was from the inhalation of fire fumes and extensive severe burns.

Under cross-examination by the prosecution, however, Dr Duflou agreed he would not exclude the possibility of Madam Low's three cuts being caused by a cleaver. The trial continues next Friday with closing submissions by both parties.