Surveillance footage showed Gaiyathiri pouring cold water on her domestic helper, slapping, pushing, punching, kicking and stomping on her.
She was also seen hitting the maid with objects, pulling her by the hair and shaking her violently, burning her with a heated iron and choking her.
The maid's meals often comprised sliced bread soaked in water, cold food straight from the refrigerator or some rice at night.
She was also made to shower with the toilet door open.
In the last 12 days of her life, she was tied to the window grille at night while she slept on the floor.
Chelvam, 42, who was suspended from service on Aug 8, 2016,
faces multiple charges in connection with the abuse of Ms Piang. Gaiyathiri's mother, Prema S. Naraynasamy, 62, who often stayed with the couple in the flat, was also charged in 2016.
Their cases are pending in court.