A 30-year-old man has been sentenced to jail for 56 weeks for hitting his mother's private parts with a metal padlock and starving her, among other abuses over several years.

The accused, Andy Koh Ju Hua, hurt his mother when he was stressed with his master's degree studies.

On March 23, the prosecutor told the court during sentencing about other abuses that were previously not revealed, CNA and Yahoo reported.

This was to provide the rationale for increasing Koh's sentence from 30 weeks jail -- the original sentence sought -- to 50 weeks instead.

Koh had pleaded guilty a week ago to four counts of voluntarily causing hurt.

Other abuses surfaced

On one occasion, Koh punched his 68-year-old mother's face, made her stand by the sink from 6:30pm to 6:30am holding an ice pack to her face, and threatened to hit her if she lowered her hands.

He also hit her on the head once with a remote control causing a scar, and only allowed her to drink plain water.

Koh hid his abuse by disallowing his mother from being seen by the public.

He made her hide from neighbours by not answering the door and wear old clothing so she could not escape to seek help.

Deputy Public Prosecutor Magdalene Huang also told the court that Koh's mother was convinced her son targeted her private region as injuries would not be noticed by others.

Son said he wants to take care of mother

Koh said in response that he wants to continue his Master's degree as he was half a year away from completion.

However, Koh's candidature was terminated in January 2021, the National University of Singapore (NUS) previously said.

He went on a leave of absence in August 2019 and did not return after the leave expired.

Koh is in remand and undergoing psychological treatment.

He said in court he wishes to be reunited with his mother in future, "live happily with her" and "take care of her in the remaining days".

According to CNA, Koh said from remand: "I also don't understand why I did all those silly things to her."

Jail term must reflect pain suffered

District Judge Kessler Soh explained that a mandatory treatment order was not an available sentencing option for one of Koh's charges under the newly enhanced provisions for victims in close relationships with the accused, according to CNA and Yahoo.

Such orders are generally suitable only for offences that carry a punishment not exceeding three years.

Agreeing with the prosecutor to up Koh's sentence, the judge said the total jail term must reflect the extent of pain, suffering and harm that Koh caused his mother, in view of the aggravating factors of the case.

The judge also took into account the Institute of Mental Health psychiatrist's assessment that Koh's offences were likely to have been substantially influenced by psychotic symptoms.

The judge noted that the case has caused "public disquiet" and it is not understood how Koh could attack his mother in such a "cruel manner"

He also stressed that it was necessary for Koh to receive treatment to minimise the risk of reoffending after his release.