A 32-year-old man who repeatedly stabbed his mother to death after voices in his head told him to do so, was on Wednesday acquitted of murder in the High Court on grounds of temporary insanity.

Mohamed Redha Abdul Mutalib had a history of substance abuse and was heavily intoxicated with pills, meant to treat a cough, two years ago when he attacked Madam Asnah Aziz in their Eunos home, according to court documents. The 56-year-old housewife died from the multiple stab wounds the same day.

In a rare case, he will instead be held in custody at Changi Prison before being transferred to the Institute of Mental Health, where he will be held at the President's pleasure.

Clearing Redha of murder under the Criminal Procedure Code, Justice Tay Yong Kwang said that while the man had committed the act, he had not been capable at the time of knowing that it was wrong.

On Jan 26, 2012, Redha, then a health-care assistant at IMH, tried to leave his flat after being woken up in the morning by noise from a lion dance performance at the neighbouring block.

After his mother stopped him from leaving, he went back to bed but heard voices in his head which told him that Madam Asnah was not his mother. These voices told him to slap her three times and if she showed fear, this was proof they were not related. Redha did this and when she reacted fearfully, another voice then told him to kill her.

He went to the kitchen to retrieve two knives, and stabbed her repeatedly in the living room.