was a Japanese tempera painter. He was convicted of mass poisoning and sentenced to death. Due to strong suspicions that he was innocent, no justice minister ever signed his death warrant. Teigin case On January 26, 1948, a man calling himself an epidemiologist arrived in a branch of the Imperial Bank (Teikoku Ginkō, aka Teigin) at Shiinamachi, a suburb of Toshima, Tokyo, before closing time. He explained that he was a public health official sent by US occupation authorities who had orders to inoculate the staff against a sudden outbreak of dysentery. He gave all sixteen people present a pill and a few drops of liquid. Those present drank the liquid he gave, which was later thought to be "nitrile hydrocyanide" (青酸ニトリール), an assassination toxicant originally developed at the Noborito Laboratory. When all were incapacitated, the robber took some money lying on the desks, which amounted to 160,000 yen (about $2,000 US at the time), but left the majority behind, leaving his motive unknown. Ten of the victims died at the scene (one was a child of an employee) and two others died while hospitalized. Arrest and trial Hirasawa was caught by the police due to the Japanese habit of exchanging business cards with personal details. There had been two other extremely similar cases of attempted and actual theft at banks via the use of poison in the weeks and months before the robbery. In all cases the poisoner, a lone male, left a business card. The poisoner used a card which was marked "Jirō Yamaguchi" in one of the two incidents, but it was later found that said Yamaguchi did not exist: the card was a fake. The poisoner also used a real card which was marked "Shigeru Matsui" (of the Ministry of Health and Welfare, Department of Disease Prevention) in another of the two incidents. The original owner of the card was found to have an alibi. Matsui told the police that he had exchanged cards with 593 people, but of these, 100 were of the type used in the poisoning incidents, of which eight remained in his possession. Matsui recorded the time and place of the business card exchange on the back of cards he received so the police set out to trace the remaining 92 cards. 62 cards were retrieved and their originators cleared; a further 22 were deemed to have been irrelevant to the case.