The widow had met the men through dating agencies, stipulating that her partners needed to be wealthy and childless.
Sentenced to death by hanging for an old millionaire in Japan for the murders of three of his spouses and a murder attempt on a fourth.
The 70-year-old's case has drawn considerable attention and earned her the moniker "Black Widow". Kakehi passed off the cyanide as a health drink, the court heard.
Before her arrest in November 2014 on a charge of killing her husband Isao, Kakehi denied murdering him, saying, "I would never do that because I would be suspected", as she was the only person living with the victim. Once named the beneficiary of life insurance policies and wills, Kakehi killed Masanori Honda, 71, and Minoru Hioki, 75, and tried to kill Toshiaki Suehiro, 79, prosecutors said. She is also accused of making money in millions from insurance payouts and her lawyers are planning to appeal the sentence.
She reportedly amassed one billion yen ($8.8m) in payouts over 10 years but subsequently lost most of the fortune through unsuccessful financial trading.More news: Roy Halladay, former Blue Jays pitcher, dies in plane crash
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But later that week, she backtracked, saying she did not remember admitting to the killing. But following his death in 1994, the business went bankrupt and her house was put up for auction, prompting her to ask neighbors for a loan.
"The cases were well prepared in advance".
The judge rejected the claim of Kakehi's innocence by her defense team, which said that the deaths of the three men might have been due to illness or accident.
"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.
The accused earlier told judges she was ready to be hanged.
The court underlined that Kakehi did not suffer dementia when she committed the last crime in December 2013. Having opened in June, it was the second-longest of its kind, with 135 days spent examining the case.