UW-Madison scientist charged after allegedly poisoning coworker's water bottle

A five-year workplace relationship at UW-Madison allegedly ended with a contaminated water bottle, a pair of tainted shoes and felony charges for a staff scientist at the university’s Influenza Research Institute. Makoto Kuroda, 41, was charged in Dane County Circuit Court on April 14, 2026, with second-degree recklessly endangering safety and tampering with a household product after an alleged incident in Madison on or about April 4.

Court papers say the coworker, identified as TM, had worked with Kuroda for about five years and that the two were initially friends. The complaint says Kuroda became upset after TM received a promotion and, in Kuroda’s view, stopped following lab rules. Investigators say the alleged conduct involved a mixture of paraformaldehyde and Trizol placed into TM’s half-drank water bottle and into TM’s shoes. The water bottle residue later tested positive for chloroform. No reports of illness or sickness were made.

The episode began when TM opened a Trader Joe’s water bottle on April 2, drank half of it, and later noticed a strange odor and bad taste. TM later noticed an odor from his shoes and reported the matter to UW-Madison police on April 6. The complaint says Kuroda later admitted to the coworker, a supervisor and police, “I did it.” Investigators also say he used ChatGPT multiple times to look up harmful amounts of paraformaldehyde and Trizol, details that point to a deliberate effort to understand the chemicals’ effects.

UW-Madison said Kuroda was taken into custody on April 10 and placed on administrative leave. The university also revoked his access to physical and digital university assets and his research privileges while it conducts its own investigation. The lab is in the 500 block of Science Drive on the University of Wisconsin-Madison campus, inside a research setting where access, chemicals and interpersonal trust are tightly intertwined.

The charges carry serious penalties. The reckless endangerment count is a Class G felony punishable by up to 10 years in prison and a $25,000 fine. The tampering-with-a-household-product count is a Class H felony punishable by up to 6 years in prison and a $10,000 fine. The case now raises a sharper question than a single criminal complaint: whether elite research environments, where long hours and hazardous materials are routine, have adequate systems to detect escalating conflict before it turns violent.