Home Team officers who were the first to turn up at the Chinatown home of American engineer Shane Todd took down his body before forensic investigators arrived.
This altered the condition of the body and the scene, said the counsel for his family at the coroner's inquiry on Monday into his death.
Dr Todd, 31, was found dead in his apartment on June 24 last year , shortly after he resigned from his job at the Singapore Institute of Microelectronics (IME). His death took place just a week before he was due to fly home to the United States.
Four responders who arrived at his apartment - an SCDF paramedic and three police officers - took the stand in the afternoon.
They testified that they brought down Dr Todd's body from a hanging position by cutting the black strap that was holding him against a door in the master bedroom. In doing so, they moved a wooden chair nearby.
"It appeared to me the condition of the deceased's body, the strap holding him up and the chair were all materially altered," said Mr Foo Cheow Ming, the Todd family's counsel.
Police Staff Sergeant Sabrina Mohamed countered that first responders to the scene were trained to bring down the body "immediately" when they encounter hangings. It was also necessary to move the chair to make space, she added.
Assistant Superintendent of Police (ASP) Tan Jun Wei, who led the police team at the scene, said it was procedure to take down the body immediately by cutting above the noose. This is to give paramedics "access to the body".
ASP Tan also said he did not observe any signs of forced entry or struggle. Dr Todd's valuables - such as his laptop, handphone and wallet - were all intact, he said.