Killer tells her story after 24 years

SAD: Trudy Tapsell was found not guilty by reason of insanity for the murder of her grandmother in 1991. PHOTO/ SUPPLIED

A piece of Rotorua's history is to be explored on TV show 3D, when a woman who killed her grandmother in 1991 will speak out for the first time.

Trudy Tapsell, daughter of former Eastern Maori MP and Police Minister Sir Peter Tapsell, was found not guilty by reason of insanity of the murder of her grandmother, 87-year-old May Tapsell, whose decapitated body was found wrapped in plastic bags in a freezer in Rotorua. Her head was found in a rubbish bag nearby.

Ms Tapsell was interviewed about the incident itself - and the months leading up to it during which she was showing signs of being mentally unwell - in the programme, which will air on TV3 on Monday night at 9.30pm.

"Looking back on it now, everybody thought I was unwell except me. But now I can look back and say, 'yeah heck I was really unwell mentally', because why would I do such a thing to anybody? Let alone somebody that I loved and who I was very close to," she said.

Ms Tapsell spent six years in Tokanui Psychiatric Hospital, where she was treated for schizophrenia. She still has monthly injections but is now recovered and works within the mental health sector.

Her brother, Rees Tapsell, who is a forensic psychiatrist and the director of clinical services for mental health and addictions at Waikato District Health Board, was also interviewed for the story.

He talks of how the family forgave Ms Tapsell, despite the tragedy they had suffered.

"Everybody deserves a second chance. Everybody," he said.

TV3 journalist Paula Penfold said interviewing Ms Tapsell was an intriguing experience.

"In the 24 years since she killed her grandmother, she's never spoken publicly of what happened and why. I admire her candour and I admire how she has since managed to turn her life around, and look after her mental health."