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Ex-nurse admits to fatally poisoning second man at Yokohama hospital

In this January 2017 file photo, Oguchi Hospital, renamed Yokohama Hajime Hospital, is seen from a Mainichi Shimbun helicopter in Yokohama's Kanagawa Ward. (Mainichi)

YOKOHAMA -- A former nurse at a hospital here who was arrested on July 7 for allegedly poisoning an 88-year-old male patient has admitted to also poisoning a second man that died two days later at the facility, sources close to the investigation have disclosed. The suspect was quoted as stating that she poisoned around 20 patients, and the police are moving forward in investigating her claim.

The 31-year-old suspect, Ayumi Kuboki, was arrested on suspicion of poisoning Sozo Nishikawa at Oguchi Hospital (currently Yokohama Hajime Hospital) in September 2016, and was sent to the Yokohama District Public Prosecutors Office on suspicion of murdering Nishikawa on July 9. Another patient, Nobuo Yamaki, 88, also died two days after Nishikawa, and Kuboki was being investigated over his death as well.

It has also been disclosed that during voluntary questioning by the Kanagawa Prefectural Police as to why she allegedly killed Nishikawa by adding disinfectant to his intravenous (IV) drip bag, Kuboki is quoted as explaining, "It's a pain to explain to families why a patient died while I was on duty and I don't like it. So, I put the disinfectant (in the IV) before my shift."

According to sources related to the investigation, Kuboki clocked in for her nursing shift at around 3 p.m. on Sept. 18, 2016, in order to prepare to take over a night shift beginning at 5 p.m. the day that Nishikawa died. Nishikawa's condition made a sudden turn for the worst at around 4:50 p.m., and a former colleague witnessed Kuboki enter the patient's room roughly five minutes earlier.

From the following information, the suspect is believed have injected the disinfectant Germitol, which contains the surface-activating agent benzalkonium chloride, through Nishikawa's IV drip so that he would die before her shift began.

Meanwhile, Yamaki's heart rate made a steep drop at around 4 a.m. on Sept. 20, 2016, and he died roughly 55 minutes later. Traces of a surface-activating substance were also detected in his body as well as his IV drip bag. Kuboki has reportedly explained that she also used the disinfectant Germitol on Yamaki.

The fourth floor of the former Oguchi Hospital, where Nishikawa and Yamaki were roommates, was a floor for end-of-life care, and saw the deaths of 48 patients between July and September 2016.

(Japanese original by Tsumuki Nakamura and Yuhi Sugiyama, Yokohama Bureau)

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