Ms Erwiana Sulistyaningsih described in vivid detail how for months she lived on nothing but bread and rice, slept only four hours a day and was beaten so badly by her former employer Ms Law Wan-tung that she was knocked unconscious.
"I was tortured," she told the packed courtroom through a translator on the opening day of the trial.
"She often hit me... sometimes she would hit me from behind, sometimes she hit me in the front. I was hit so often sometimes I got a headache... She hit me in my mouth (so) I had difficulty breathing."
Law denies all charges of abuse.
Ms Sulistyaningsih's case has shone a spotlight on the plight of migrant domestic helpers in Asia and the Middle East after reports of torture and even killings.
In March, a Malaysian couple was sentenced to hang for starving their Indonesian maid to death, while in the same week a Singaporean couple pleaded guilty to abuse after their helper lost 20 kilos in seven months.
Such cases have prompted a clampdown on domestic worker visas in some countries, Myanmar suspended a seven-month-old scheme in September and Indonesia has pledged to stop sending domestic workers abroad from 2017.
Hong Kong is home to nearly 300,000 maids, mainly from Indonesia and the Philippines.
Thousands took to the streets in May calling for better working conditions and greater legal protection for domestic helpers and the case remains a rallying point for many.
Amnesty International last year condemned the "slavery-like" conditions faced by some domestic helpers in the southern Chinese city, and accused authorities of "inexcusable" inaction.
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