A former nurse in Japan is admitting to sabotaging intravenous drips in a mass poisoning case that police believe led to the deaths of dozens of hospital patients.

Police arrested 31-year old Ayumi Kuboki over the weekend in the death of 88-year old Sozo Nishikawa at Yokohama's Oguchi hospital two years ago.  Ms. Kuboki reportedly told investigators that she injected disinfectant into the intravenous drip bag at the end of her shift so that the patient would die when she wasn't at the hospital.

The reason, she told police, was that she didn't want to have to face the grieving families, so she timed it to avoid facing bereaved families.  So that grieving families would be someone else's problem.

Investigators were able to backtrack the crime to her because the disinfectant chemical, benzalkonium chloride, was present only on her uniform and not on her coworker's clothing.  Staff subsequently found puncture marks in ten of about 50 unused drip bags stored near Kuboki's nurses' station.

Police don't necessarily believe her claim that she only targeted critically ill patients who were going to die anyway.  About 48 patients at the hospital died in unusual circumstances over a three-month period in 2016, including five in a single day.