Carlotta Brett-Pierce and her mother, Loretta Brett, have pleaded not guilty in the death of Marchella Pierce.
Their trial started Monday.
Marchella was found dead in 2011. She had been tied to a bed, and weighed 18 pounds, nearly half the weight of an average 4-year-old.
Brooklyn prosecutors say she had been beaten. They also say she had up to 30 adult doses of Benadryl and 60 doses of Claritin in her system.
Authorities say she died from battered child syndrome.
Two child welfare workers assigned to her case are awaiting trial.
The case prompted reform by the city's child welfare agency.
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