Japan's 'Black Widow' serial killer, who murdered 3 lovers, loses execution appeal

• Chisako Kakehi, 74, poisoned two boyfriends and a husband with cyanide between 2007 and 2013.
• She was put on death row in 2017.
• Her lawyers argued that she suffered from dementia, but the appeal was dismissed.

A 74-year-old woman known as Japan's "Black Widow" has lost her appeal against death row for the murder of three male partners, including her husband, reported Japanese broadcaster NHK.

Chisako Kakehi was sentenced to death 2017 for poisoning the three men, who were between the age of 70 and 80, with cyanide between 2007 and 2013. One was her husband, while the other two were her lovers.

She was also charged for the attempted murder and robbery of another man, reported The Japan Times.

All four were part of a larger list of 10 men she had married or was associated with, and from whom she inherited a total of $9 million that she later lost in the stock market, reported the Times.

Out of the that list, three of Kakehi's other husbands are also dead, though she has not been charged for their deaths, said the BBC.

In her 2017 trial, it was stated that Kakehi used a matchmaking service to meet her partners, narrowing down her requests to wealthy men who had no children, the BBC reported.

Kakehi's lawyers argued that she suffered from dementia, but the appeal was dismissed by the Supreme Court, and her death sentence is now final.

Murders in Japan are a rarer occurrence than in the US, with a homicide rate of 0.25 out of 100,000 people compared to America's national rate of 5.6 out of 100,000 people, according to the UN.

But serial killings have still made Japanese headlines recently, such as a "Twitter Killer" who pleaded guilty last year to dismembering nine people in 2017 when they expressed suicidal thoughts on Twitter.

In the meantime, serial killer rates in the US have dropped, with the FBI saying that they account for less than 1% of all homicides in America.