A Gisborne woman's died in a police cell overnight- a day after being convicted of her father's murder.

63-year-old Lynne Maree Martin was yesterday found guilty of killing 88-year-old Ronald Allison by burning down his house.

After what was thought to be forever a cold case, his daughter was arrested and charged with murder just last year.

ZB reporter Chelsea Daniels says it was revealed a police officer went undercover to gain Martin's trust during the investigation.

"The officer, who called herself Millie, slowly befriended Martin and her husband Graham in about 2020. She was wearing a wire and the jury heard a raft of conversations between the pair."

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