The Numazu Family Court on Wednesday was handed the case on a 16-year-old girl who has been detained since late last year on suspicion of poisoning her mother.

The girl, whose name is being withheld because she is a minor, has been in custody since late October, following her arrest on suspicion that she attempted to kill her 48-year-old mother in Izunokuni, Shizuoka Prefecture, by lacing her food with thallium, a substance often used as rat poison.

She has consistently maintained her innocence, although a diary she kept reportedly indicated otherwise.

Shizuoka Prefectural Police, however, have concluded that the girl is the only one who could have committed the crime because she was the only person who had bought thallium in the prefecture within the last five years, investigative sources said.