The 37-year-old, identified in court only as L.S.T., pleaded guilty on June 22 to manslaughter and cruelty to a child before her sentencing on Aug. 5, RTHK reported.

Madam Justice Susana D'Almada Remedios took 30 years as her starting point on the manslaughter count and cut it to 20 for the guilty plea, according to court news outlet The Witness, adding two years drawn from a six-year, four-month term for child cruelty.

Manslaughter carries a maximum of life imprisonment in Hong Kong.

The boy, referred to in court only as Z, was found unconscious in bed at the family's subdivided apartment in Sham Shui Po on Sept. 2, 2022, after his mother called police to report that he had died, HKFP reported.

He was one meter (3 feet 3 inches) tall and weighed 9.7 kilograms (21.3 pounds), about half the normal weight for his age, the South China Morning Post reported.

An autopsy recorded 129 injuries and signs of prolonged abuse including force-feeding, gagging and violent rubbing, according to the newspaper, which quoted the judge saying the crime exposed a "savage nature utterly devoid of the empathy inherent to motherhood."

The Standard, citing expert evidence heard by the court, reported that Z had likely gone hungry for 61 to 91 days and that his organs and muscles had atrophied.

D'Almada Remedios rejected the defense argument that the woman's limited education explained her conduct, The Witness reported, noting she had cared adequately for her other children and singled Z out, keeping him from school and confining him to a bedroom where he ate and relieved himself. Her eldest daughter told police the boy was tied to the bed and let out only a few times a week.

The judge said the mother had not acted in a flash of rage, calling the killing "a protracted, cold-blooded annihilation carried out with the patience of a torturer," according to RTHK.

The court heard the woman had two 2018 convictions for drug possession. She had told a friend she did not like Z, then called the same friend in tears months later to say she had beaten him to death, The Witness reported.

Z had been placed in foster care and a children's home as an infant and returned to live with his mother in August 2020, after a December 2019 hospital assessment concluded she could care for her children under supervision, The Witness reported. Social workers went on to see him in person on Dec. 1, 2021, in April 2022 and in June 2022.

At that final visit, three months before Z died, a Social Welfare Department worker reported observing no visible injuries on his face and nothing irregular, SCMP reported.

The department then concluded the abuse element had subsided and transferred the family to another welfare organization, according to the newspaper.

The new worker discovered Z had been absent from nursery for more than two-thirds of the school days across two academic years, then learned of his death from news reports on Sept. 3 while trying to reach the mother.

A pediatrician had already documented that Z's height and weight were abnormal for his age, the judge noted, making it incomprehensible that the visits turned up nothing.

"It strains the imagination to think that Z's life may have been spared," she said, according to HKFP.

In a mitigation letter cited by The Witness, the woman said she was deeply remorseful and could not forgive herself. She wrote that she had neglected Z and failed to seek medical help while pregnant with a fourth child and in frequent conflict with her boyfriend, the boy's father.

Her three surviving children are now in Social Welfare Department foster placements.

Hong Kong's Mandatory Reporting of Child Abuse Ordinance took effect on Jan. 20, 2026, more than three years after Z's death, imposing a statutory duty on 25 categories of social welfare, education and healthcare professionals to report suspicions of serious harm to a child as soon as practicable.