The expert witness who suggested that American researcher Shane Todd was murdered, has recanted part of the findings in his post-mortem report.

Dr Edward Adelstein, who was testifying at a coroner's inquiry on Tuesday via video-link from the United States, now says Dr Todd had not been garrotted - a term that means strangulation with a wire or cord. He says he now agrees with the reports by four other pathologist that it was not a garrotting because of the absence of broken blood vessels and neck injuries.

But he maintains that Dr Todd was killed, possibly by more than one man "because Shane is well-built, there must have been more than one assassin".

The body of Dr Todd was found hanged in his apartment last June but his parents believed he was murdered and had engaged Dr Adelstein to produce an independent post-mortem report.

He was initially supposed to testify to his report that their son - whom they believed was killed over his work at the Singapore Institute of Microelectronics (IME) - was strangled but changed his position when confronted by the State Counsel.

Dr Adelstein's earlier report was also the only one, out of five commissioned, which concluded that it was murder. Two of those reports from independent overseas experts engaged by the State had concluded it was suicide, while veteran pathologist, Dr Wee Keng Poh from the Health Sciences Authority, had testified last week that Dr Todd died from hanging.

Medical evidence supported that finding said Dr Wee, who has conducted more than 10,000 autopsies, including at least 800 cases of asphyxia due to hanging.

Dr Adelstein had told the court earlier that he is not a published forensic pathologist but medical examiner and a trained veterinarian. At the time of the review of Dr Todd's case last October, he had dealt with 25 hanging cases.