HONG KONG — A serial murder trial in Japan took a cinematic turn this week when the accused, nicknamed the Black Widow by the news media, confessed in open court to having fatally poisoned her husband.

The case of Chisako Kakehi, now 70, has gripped Japan since her arrest in 2014, when the last of her four husbands, Isao Kakehi, a 75-year-old retired salaryman, was found dead at his home in Muko, a city near Kyoto, the latest in a string of her partners to have died.

“I killed my husband,” Mrs. Kakehi said from the witness stand on Monday. “I have no intention of hiding the guilt. I will laugh it off and die if I am sentenced to death tomorrow,” she said, according to The Japan Times.

According to the authorities, Mr. Kakehi was one of six men who died soon after marrying or dating Mrs. Kakehi, the onetime proprietor of a T-shirt printing business. Mrs. Kakehi has been on trial since June 26, accused of killing Mr. Kakehi and two other boyfriends and trying to kill another man she had dated.