SINGAPORE - Unhappy that a psychiatrist had rejected his request that his mentally ill son be discharged from the Institute of Mental Health (IMH), a retiree punched him several times.

Japanese national Morio Sato, 62, was on Monday (Nov 27) jailed for 10 weeks after he admitted to throwing punches at Dr Sajith Sreedharan Geetha, 49, a senior consultant, on the right forearm, intending to cause him hurt, at Clinic B, IMH, at about 9.30am on Dec 8, 2016. The psychiatrist suffered tenderness and a bruise on his right forearm.

Two other charges of punching and kicking an Aetos security officer, and pushing a medical worker were considered during sentencing.

Deputy Public Prosecutor Quek Jing Feng said Sato's 29 year-old son, diagnosed with autism spectrum disorder, moderate intellectual disability and attention deficit hyperactivity disorder, was admitted to IMH on July 19, 2016 under the Mental Health (Care and Treatment) Act. His parents were unable to handle him because of his aggressive behaviour at home.

Sato and his wife attended a series of family conferences at the IMH. Dr Sajith explained the need to continue detaining their son but Sato was generally resistant to the treatment suggestions of the IMH medical team.

At a session on Nov 7 last year, Sato insisted that his son be discharged, but Dr Sajith told him of his son's multiple incidences of aggression at IMH. Sato was asked but could not give an assurance that he would not get into a physical altercation with his son if he was discharged from the IMH.

On hearing that he could not go home, Sato's son became distressed and slapped his head repeatedly. Sato blamed the doctor and his team for the situation, and demanded that his son be discharged immediately. He created a commotion.

On Dec 8, Dr Sajith handed a memo to Sato to explain the reasons for his son's continued detention at IMH.

After reading the memo, Sato again sought the immediate discharge of his son, but this was rejected by Dr Sajith because the patient required further treatment.

On hearing this, Sato became agitated and lunged towards Dr Sajith, shovingaside medical social worker, Kelly Koh Ching Ling, in the process, causing her to fall to the ground. Sato threw punches at Dr Sajith who used his arm to block them.

The panic alarm was triggered to activate the IMH crisis response team. When the Aetos security officer tried to restrain Sato, he punched and kicked him.

He continued to try and attack the victim even as security officers tried to restrain him. Police were called and Sato was arrested.

Sato's lawyer, Mr Ahmad Firdaus Daud, assigned by the the Criminal Legal Aid Scheme, said in mitigation the offences arose from a momentary lapse of judgment.

"This was a one-off burst of violence caused by pent-up frustrations over a long period of time given the stresses of his son's detention in IMH and his wife's cancer treatments," he told the court.

Sato, who has been living in Singapore for more than 10 years, thought that his son would be warded and treated like a patient in a hospital and did not realise that he was being legally detained and the implications of that, said the lawyer.

Sato could have been jailed for up to seven years and/or fined for causing hurt to a public servant in the discharge of his duty.