Police say a dispute inside a campus flu research lab led to chemicals being placed in a water bottle and shoes.

MADISON, Wis. — A staff scientist at the University of Wisconsin-Madison has been charged with two felonies after police said he admitted putting laboratory chemicals in a co-worker’s water bottle and shoes following a dispute tied to a promotion.

Makoto Kuroda, 41, is accused in Dane County Circuit Court of second-degree recklessly endangering safety and tampering with household products. The case grew from a complaint inside the university’s Influenza Research Institute, where staff reported a strong chemical odor in an office. University police said the episode appeared isolated, but it triggered a criminal case, a campus workplace investigation and a ban from university labs.

The first warning came from a plastic water bottle left on a desk. According to the criminal complaint, the co-worker, identified in court records as TM, opened a new Trader Joe’s water bottle on April 2, drank about half and left it in his office. When he returned April 4, he noticed a strange odor and a chemical taste, then spat out the water. On April 6, he noticed the same odor from lab shoes kept under his office table. Another employee smelled both items and felt the matter should be reported, even though TM at first did not want to make a big issue of it.

UW-Madison police were called April 6 at about 1:13 p.m. to the Influenza Research Institute in the 500 block of Science Drive. Officers later worked with the Madison Fire Department Hazardous Incident Team, which collected the water bottle and helped move it to the Wisconsin State Laboratory of Hygiene. A preliminary test found chloroform in residue from the bottle, with a level described in the complaint as too high for test strips to give an accurate value. Police wrote that the result was concerning because chloroform dissipates over time, meaning the original exposure could have been significant.

The investigation turned on April 10, when police said Kuroda admitted his role to the co-worker and to supervisors. TM told Officer Adrian Vera that Kuroda came up to him in the lab and said, “I did it,” then made a comment about his shoes. TM said he felt scared and left for another co-worker’s office. A supervisor, identified as YK, told police that Kuroda also sent an email in Japanese that said, “I did it. I have also informed the person himself. I am very sorry.” YK and Kuroda are both native Japanese speakers, according to the complaint.

Police said Kuroda told officers he had worked with TM since 2017 and had become upset over workplace conduct. The complaint says both men had been promoted, but TM later received another promotion while Kuroda did not. Kuroda told police he believed TM’s attitude changed after that promotion and that TM acted as if he were better than him. He also cited smaller grievances, including claims that TM did not wear a lab coat and goggles when supervisors were not present and crossed a hallway in a way Kuroda found disrespectful.

Kuroda told police he returned to work on April 5, moved between his office and the lab, then saw a half-full bottle on TM’s desk, the complaint says. He said he used a syringe to take paraformaldehyde mixed with Trizol from a work refrigerator and placed about 0.5 milliliters of 4% paraformaldehyde in the water bottle. He also wrote for police that he put 1.5 milliliters of Trizol and 1.5 milliliters of 4% paraformaldehyde, mixed together, in each shoe. The complaint says the process took about 10 minutes, after which he threw away syringes and put the vials back.

The chemical list remains part of the continuing inquiry. UW-Madison said the substances are alleged to be paraformaldehyde, chloroform and Trizol, chemicals routinely found in many research laboratories. The university said final analysis from the Wisconsin State Laboratory of Hygiene was pending. The complaint says Trizol is used to separate RNA and that a Trizol mixture used at the institute contains chloroform. It also says Kuroda had unrestricted access to paraformaldehyde and Trizol and told police he had used paraformaldehyde for about eight years.

No illness was reported in the complaint. Still, Kuroda allegedly told police he expected TM to get sick. He said paraformaldehyde could cause mouth and throat irritation, stomachache, vomiting and dizziness if consumed. He also said the mixture in the shoes could cause rash or discomfort. “My aim was just, he feel bad,” Kuroda told police, according to the complaint. When asked how he would feel if TM had drunk the water and died, Kuroda sat silent for about 30 seconds before saying, “I, I shouldn’t do that,” the complaint says.

Investigators also described gaps in how one chemical was tracked in the lab. Another employee told police chloroform was available in the institute’s lab and annex lab, that all employees had access to it during the day, and that it was locked after everyone left. The employee also said there were no cameras showing where chloroform was stored or used and no procedures or records for its use. The university said the alleged conduct was unrelated to the research at the institute and said there was no evidence that research materials, other than routine laboratory supply chemicals, were involved.

The Influenza Research Institute studies viruses that cause illnesses such as flu and COVID-19, according to the university. UW-Madison said the lab is subject to safety and security measures under university policies and law. The university said employees who work there must be approved by the Federal Select Agent Program after an FBI security risk assessment at hiring and every three years afterward. UW-Madison said it was in contact with the FBI after Kuroda’s arrest and that lab members receive training on protocols, including personal protective equipment.

Kuroda was arrested Friday evening, April 10, and the Dane County District Attorney’s Office filed the charges April 14. Court records and jail records list the case as 2026CF000839. The reckless endangerment charge is a Class G felony, while the tampering charge is a Class H felony. Together, the two charges carry a possible maximum of 16 years in prison and $35,000 in fines if Kuroda is convicted. He has not been convicted, and the allegations remain pending in court.

UW-Madison said Kuroda is on administrative leave while the university conducts a workplace investigation. His access to physical and digital university assets and his research privileges have been revoked, the university said. Court records cited by news outlets said he was ordered not to contact TM and not to go on the UW-Madison campus or into university laboratories. The Dane County Sheriff’s Office listed him as a pretrial resident at the Public Safety Building after his April 10 booking.

The case now sits in both the court system and the university’s internal process. Police said the investigation was ongoing and that additional charges could be filed. The next major steps include further chemical testing, continued review of the workplace dispute and the next scheduled court date listed in public reports. The university said employee privacy laws and the pending criminal case limited what else it could release.

Author note: Last updated 2026-05-06.