The Third Petty Bench of the Supreme Court, in a 5-0 decision Tuesday, upheld lower court rulings that sentenced a Wakayama woman to death for killing four people and poisoning 63 others by lacing a curry stew with arsenic during a community summer festival in July 1998. This was a difficult and unusual case. There was no direct evidence linking defendant Masumi Hayashi to the killings, and even her motive remained unclear.

Expert analysis determined that the arsenic in the stew was the same as the arsenic found in her home. The defense said that the analysis was lax. A witness account said that Hayashi was seen minding the stew pots alone. The defense argued that the person seen could have been Hayashi's daughter. Besides the curry poisoning case, Hayashi was found guilty of attempting to kill her husband and acquaintances using arsenic, with the aim of claiming life insurance money.

The top court decided that circumstantial evidence, including a high concentration of arsenic found in Hayashi's hair, proves, "to a degree that excludes any rational doubt," that she was the only person who had an opportunity to put arsenic in the pots of curry. As to her motive, the prosecution said that Hayashi was infuriated over her neighbors' attitude toward her, which made her feel alienated from society. Both the district and high courts said that her motive was unclear. But the top court said that the failure to pinpoint the motive does not affect the judgment that she was the culprit. One wonders whether more could have been done to determine the motive.