The murders appear to have been motivated by money, and she even met some of her victims through a matchmaking service that targeted men with a high income.
A serial killer dubbed the "black widow" was handed a death sentence Tuesday over the murders of her husband and two common-law partners, as well as the attempted murder of an acquaintance, between 2007 and 2013.
Kakehi earned the nickname "Black Widow" for her comparisons with the spider that kills its mate after copulation. Kakehi passed off the cyanide as a health drink, the court heard. She was later indicted in connection with the deaths of the two other men. Kakehi's lawyers filed an appeal. She married or was associated with more than 10 men and inherited about 1 billion yen, though she eventually fell into debt following her attempts to speculate in stocks and futures trading.
The presiding judge concluded that Chisako Kakehi, 70, committed these crimes after persuading the men to take out life insurance policies in her favour.
During the trial Kakchi admitted to killing Isao Kakehi, saying he had not treated her well financially, but later retracted it. However, the one-time millionairess went bankrupt and was debt-ridden.
Ms Kakehi was accused of murdering her fourth husband, 75-year-old Isao Kakehi, on 28 December 2013, a month after they got married. They accused her of plotting her crimes well in advance, including helping to prepare notary documents linked to wills. She had said later to the judges that she was ready to face the death penalty: "Even if I was being executed tomorrow, I would die with a smile ".
She had relationships with many men, mostly elderly or ill, meeting some through dating agencies, where she reportedly stipulated that prospective partners should be wealthy and childless.
Her defence argued that Kakehi was not criminally liable because she had suffered from dementia - an argument rejected by the judge. Having opened in June, it was the second longest of its kind, with 135 days spent on examining the case.
"Disregarding human life, Kakehi's crimes were well-planned and malicious", said judge Ayako Nakagawa, who presided over the lay judge trial, handing down the death sentence as demanded by public prosecutors.