How Japanese Nurse Ayumi Kuboki Slowly Murdered Some Of Her Patients

Although nurses are not required to do take an oath to do no harm, American Mobile writes that they are expected to adhere to ethical standards. Nevertheless, there have been several cases where medical professionals use their careers to murder. A&E reports that this is a rare phenomenon that typically manifests in nurses rather than doctors. Per the Independent, Ayumi Kuboki was one such nurse. In 2016, the then 31-year-old was working at the Oguchi Hospital in Yokohama, Japan.

The Independent notes that Kuboki became a nurse in 2008 and had previously worked at another hospital before she was hired at Oguchi. By all accounts, Kuboki appeared to be a dedicated nurse. One of her coworkers stated, "She was the kind of person who was hard to figure out what she was really thinking, but she was considered competent" (via the New York Post). However, suspicion arose when two elderly patients, Sozo Nishikawa and Nobuo Yamaki, died within days of each other in the fall of 2016. The 88-year-olds shared a room and another nurse noticed that Yamaki's IV bag had bubbles in it. In other words, the IV had been tampered with.

The Independent writes that an autopsy was performed on Yamaki and it was concluded that he had been poisoned with an antiseptic solution. Per the Daily Mail, an autopsy was then performed on Nishikawa. He too had died from the same poison. A subsequent investigation began at the hospital and officers discovered several punctured IV bags (via the New York Post). It was determined that Yamaki and Nishikawa's killer had likely inserted the poison with a syringe. The police decided to inspect the nurses' uniforms and traces of the antiseptic were found only on Kubokis. When she was arrested and questioned, Kuboki confessed to her crimes.

She stated (via the Independent) that she poisoned "about 20 patients” including Yamaki and Nishikawa, by injecting antiseptic into their IV bags. According to the New York Post, the antiseptic Kuboki used contained a chemical called benzalkonium chloride. VICE reported that Kuboki disclosed that she was "mentally and physically exhausted" from being a nurse. Furthermore, she explained that she opted to kill patients that she believed were near death.

According to the Independent, she did not want them to die during her shift. If they did, Kuboki was tasked with breaking the news to family members and she wanted to avoid this at all costs. Kuboki noted (via the Independent), "It would be troublesome if that responsibility fell on me." Thus, she killed her patients while there was still another nurse on duty. Kuboki, for example, poisoned Nishikawa before the start of her shift.

In November 2021, Ayumi Kuboki was convicted of killing three patients at Oguchi Hospital (per the Independent). The Japan Times reports that they include Nishikawa, Yamaki, and 78-year-old Asae Okitsu. During her trial, Kuboki apologized to her victim's loved ones. Presiding Judge Kazunori Karei decided to sentence Kuboki to life in prison. He noted that he did not want to give Kuboki the death penalty because she showed remorse. The Judge stated, (via The Japan Times) "She understands the huge gravity of the crimes, and even said in her final statement she wants to make amends with her own death."

He added, "By having her face the weight of her guilt for the rest of her life, it is fair to have her back on the right track in life." Although Kuboki will forever be behind bars, VICE writes that her victims' family members were dismayed by her sentence. Yamaki's son expressed his disapproval and said, "It's strange that she wasn't sentenced to death for killing innocent people while having such selfish motives." Weeks after this verdict, prosecutors sought to appeal her life sentence, per The Japan Times. At the time of this publication, the status of this appeal is unknown.