• Kyodo


A 31-year-old former nurse was turned over to prosecutors Monday after being arrested Saturday for allegedly murdering an elderly patient in 2016 at a Yokohama hospital where three other patients also died under suspicious circumstances, police said.

Ayumi Kuboki has admitted to killing Sozo Nishikawa, 88, who died Sept. 18, 2016, at what was then named Oguchi Hospital, according to the police. He was found to have been poisoned with a surfactant compound.

Kuboki told them she injected disinfectant into intravenous drip bags being administered to about 20 patients, according to investigative sources.

The sources said Monday that Kuboki told investigators that when a patient dies, a nurse on duty at the time has to explain the details to the person’s family, and that she found this bothersome.

Investigators found that a surfactant compound appeared to have been put into Nishikawa’s drip bag around the time Kuboki’s shift was ending, and believe that she wanted the patient to die after she had finished work for the day.

Traces of a surfactant compound were also found in the bodies of the three other patients who died.

One of them, Nobuo Yamaki, 88, died two days after Nishikawa in the same room.

The same type of toxic substance was found in his body and in an intravenous drip bag that had been used to treat him, according to the police.

Kuboki has reportedly told the police she repeatedly injected disinfectant into drip bags. She remains under investigation over the other deaths.

In 2016 from July to September, 48 patients died at the hospital, including five on a single day in late August and four on one day in early September.

The substances found in their bodies were the same as the disinfectant used at the nurses’ station on the hospital’s fourth floor, where both Nishikawa and Yamaki were staying.

Among about 50 unused drip bags at the nurses’ station, about 10 were found to have small puncture holes in them. The police believe a syringe was used to inject the disinfectant into the bags.

Soon after Nishikawa and Yamaki died, police began investigating the case as a possible murder committed by someone with knowledge of the hospital and medicine.

Shortly after they began investigating the deaths, Kuboki said that she was not involved in the incidents and had not noticed anything unusual at the hospital.

Before she was arrested, Kuboki flatly denied lacing IV drip bags with poisonous substances. She said she was “shocked” by the incidents and “felt very sorry for the victims as well as their families.”

Beginning about six months before Nishikawa’s death, the hospital saw a series of suspicious incidents. In April 2016, shredded nurses’ aprons were found, in June part of a patient’s medical records was lost and in August a nurse tasted what she believes was bleach in a bottled drink.

According to her mother, Kuboki said she was afraid of working at the hospital at night and wanted to quit her job.

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