Chisako Kakehi, 70, was sentenced to death for the murder of three men, including her husband, and the attempted murder of another.
The Kyoto District Court acknowledged that Chisako Kakehi, 70, used cyanide in the four cases and determined that she is competent to stand trial and can be held responsible for the crimes despite having been diagnosed with dementia in a psychiatric test. She was also charged for the attempted murder of another.
The sentencing comes nearly a month after prosecutors sought the death penalty for her, describing her crimes as "heinous and serious incidents that are rarely seen". "I have no choice but to impose the ultimate penalty", the judge said.
Kakehi earned the nickname "Black Widow" for her comparisons with the spider that kills its mate after copulation.
Nakagawa said Kakehi "made light of human lives" as she repeatedly committed the killings, adding that she offered "almost no words of apology" and had not reflected on her crimes.
Her defence argued that Kakehi was not criminally liable because she had suffered from dementia - an argument rejected by the judge. She tricked her victims into drinking the poison, telling them that the drink was a health cocktail. Her lawyers plan to appeal the sentence. She would then trick them into making her the beneficiary of their insurance payouts and later kill them using cyanide which she had kept hidden in a plant pot at her home.
Her murderous web won't protect Japan's "black widow", who's been sentenced to hang after a months-long trial.
In the case's first public hearing, Kakehi said she would leave everything to her lawyers, but her statements during proceedings lacked coherence, including a stunning confession that she had killed her husband in 2013. She is widely referred to in Japanese media as The Poison Lady.
Judge Nakagawa noted that cyanide was detected in one of the three murdered victims and the man who survived, and recognized that the other two died of cyanide poisoning based on their condition when they were taken to hospital by ambulance.
She married first at the age of 24 and launched a fabric printing company in Osaka Prefecture with her first husband. However, the one-time millionairess went bankrupt and was debt-ridden.