Chisako Kakehi, now 74, is on death row for murdering three romantic partners and the attempted murder of a fourth.
The murders started in 2007, when she was 61, but she escaped suspicion until Isao Kakehi’s death prompted a police investigation that resulted in her arrest in 2014.
https://edition.cnn.com/2021/09/25/asia/japan-black-widow-killer-intl-hnk-dst/index.html