A family court on Monday ordered that a 17-year-old girl be sent to a juvenile correctional institution for attempting to murder her mother with poison last year at their home in Izunokuni, Shizuoka Prefecture.
The girl, who attended a prefectural high school, was arrested Oct. 31 for putting thallium, a chemical used for rat poison, in her mother's drinks. The mother is hospitalized and remains in a coma.
The girl initially denied the charge but later told the Numazu branch of the Shizuoka Family Court that she had laced her mother's drinks with thallium.
One of her relatives said in a letter made public in December that they have no idea why she poisoned her mom.
According to police, the girl put thallium in her mother's drinks and food between last August and October.
The girl purchased the chemical from a pharmacist, saying she wanted it for laboratory experiments in extracurricular activities at her school, according to police.
She recorded changes in her mother's condition and published them on an Internet blog, they said, noting the girl's name has been withheld because she is a minor.
Investigators found several types of drugs and small animal carcasses in her room at home, along with a biography of Graham Young, a British man who used poison to kill three people, including his stepmother, police said.