University of Wisconsin lab poisoning: Co-worker charged after ‘I did it’ confession

Kuroda allegedly admitted to poisoning his co-worker. Photo / Dane County

A University of Wisconsin lab worker who was resentful of his colleague’s behaviour and promotions allegedly tried to poison his water and shoes.

The victim, named TM, told police he had noticed a strange odour coming from his Trader Joe’s water bottle on the afternoon of April 4. When he drank from it, it “had a bad taste” and he spat the water out, according to the complaint.

Then he noticed the same odour coming from his office – this time traced to his lab shoes, which he kept at work and never took home.

TM’s co-worker, Makoto Kuroda, 41, is charged with recklessly endangering safety and tampering with a household product with the intent to kill, injure or endanger the health of another person, according to a criminal complaint filed in Dane County.

Kuroda allegedly admitted to poisoning his co-worker. Photo / Dane County

According to the complaint, Kuroda walked up to TM in the lab and said, “I did it”.

Kuroda told police he had grown frustrated with TM over years of perceived slights: a promotion TM received that he did not, refusal to wear a lab coat unless supervisors were present, cutting in front of him in the hallway, and once throwing rubbish into a bin loudly nearby.

The stress kept “growing and growing,” he said, until it made him “do this”.

On the evening of April 5, he returned to the lab, spotted TM’s half-full water bottle, and used a syringe to place a mixture of paraformaldehyde (PFA) and trizol into the bottle and each of TM’s shoes. It took about 10 minutes.

He told police even one microlitre of paraformaldehyde would cause mouth and throat irritation, and the amount he used would likely cause “a stomach ache, vomiting and dizziness” – and that anyone who drank it should see a doctor.

According to Kuroda, someone would have to drink 10ml of PFA for it to be lethal. He told the investigators he only put 0.5ml in the water bottle.

Kuroda said he used Chat GPT to look up what a harmful amount of PFA and trizol was for a human. Each time ChatGPT gave him a number for what could be ingested, and Kuroda brushed off warnings from the chatbot about his questions, according to the complaint.