Masumi Hayashi (poisoner)

Masumi Hayashi (林 眞須美, Hayashi Masumi, born July 22, 1961) is a Japanese woman convicted of putting poison in a pot of curry being served at a 1998 summer festival in the Sonobe district of Wakayama, Wakayama, Japan.

A communal pot of curry being served to residents of Sonobe district, Wakayama, was poisoned with at least 1,000 grams of arsenic — enough to kill over 100 people — on July 25, 1998.

Two children and two adults died after consuming the curry, and 63 others suffered from acute arsenic poisoning. Killed in the incident were 64-year-old Takatoshi Taninaka and 53-year-old Takaaki Tanaka (council president and vice president of Wakayama, respectively), 10-year-old Hirotaka Hayashi, and 16-year-old Miyuki Torii.

Attention quickly focused on 37-year-old mother of four Masumi Hayashi, as she was seen by a witness at the curry dish, and she had easy access to arsenic because her husband was an exterminator. Prior to the murders, Masumi had been an insurance saleswoman. After her arrest, she and her husband were indicted on a number of insurance fraud charges as well. Masumi was also tried for three other attempted murders by poison that had occurred during the previous 10 years, with the motive in those cases being life insurance benefits. She is believed to have tried to kill her husband at least once. Her motive for poisoning the curry has been said to be anger at her neighbours for shunning her family. The arsenic found in the curry was identical to the arsenic she had in her own home from her husband's extermination business.

At her trial she pleaded innocent, but she was sentenced to death in 2002. On June 28, 2005, a high court in Osaka upheld her death sentence. However, her lawyers (Yoshihiro Yasuda among them) insisted on her innocence because only circumstantial evidence existed.

On April 21, 2009, the Supreme Court of Japan rejected her final appeal.

In July 2009, Hayashi formally petitioned for a retrial. The court's decision is pending.

Hayashi's case gained public attention. The crime inspired a wave of copycat poisonings.