Chisako Kakehi, on trial in the Japanese city of Kyoto, confessed to obtaining cyanide from a business associate to use on her husband in late 2013.
Her lawyers had pleaded not guilty on behalf of Ms Kakehi, as per her instructions.
Japanese newspaper Mainichi reports that despite this, during questioning on July 10, when asked if she murdered her 75-year-old husband, she replied there was “no mistake.”
“I killed my husband,” she told the Kyoto District Court.
Asked about her motive, Ms Kakehi, dubbed the "Black Widow", said she became upset after believing he had been treating her poorly financially in comparison to the last woman he was involved with.
The 'Japan Times' newspaper said she claimed to have tricked him into taking the poison, most likely by placing it in a health food capsule.
The pensioner added that even if she was sentenced to death, she would “laugh it off.”
The 70-year-old former printing company operator was arrested in 2014.
Prosecutors maintain Ms Kakehi has been targeting men for their money, and believe she used cyanide on all of her alleged victims.
A case was opened after her fourth husband, Isao Kakehi, died just a month after they got married.
An autopsy revealed traces of cyanide in his body, leading investigators to probe the deaths of several of Ms Kakehi’s previous lovers.
She has been charged over the deaths of Mr Kakehi and two other boyfriends, as well as for the attempted murder and robbery of another boyfriend who later died of cancer.
No charges have been laid over the deaths of Ms Kakehi’s three other husbands.
The men were all aged between 70 and 80 years of age when the crimes supposedly occurred.
Ms Kakehi’s attorneys argued that her testimony can’t be trusted as she is suffering from dementia. But prosecutors said she is still competent enough to stand trial.
According to the 'The Japan Times', more than ten men romantically associated with Ms Kakehi have died.
The paper reports the trial is expected to continue until November 7.
- with wires
