Inquest Hears Killer's Early-Onset Psychosis 'Extremely Rare'

A coronial inquest into the death of a 10-year-old girl has heard it is "extremely rare" for a person of her killer's age to develop psychosis.

The NSW State Coroner Teresa O'Sullivan is examining the circumstances leading up to the death of Bridgette "Biddy" Porter in rural NSW in July 2020.

In 2021 the Supreme Court found her killer, referred to as "XR" during the inquest, not criminally responsible for mental health reasons. They were detained in a forensic health facility.

Forensic psychiatrist Olav Nielssen told the coroner that XR "had an early onset form of schizophrenia", which he described as a "severe form of mental illness".

Dr Nielssen, one of the final witnesses to give evidence, told the inquest he had not interviewed XR but based his diagnosis and findings on written reports, a police interview and assessments clinical experts conducted on XR.

Dr Nielssen said the condition presented as an abnormality in neurological function that affected thinking, emotional regulation, and caused central disturbances in auditory hallucinations and delusional beliefs.

Counsel assisting the coroner Peggy Dwyer SC asked the witness if it was "extremely rare" for a person of XR's age, at the time of Biddy's death, to develop psychosis.

"Yes, I don't know of another case," Dr Nielssen said.

He told the inquest that the "typical onset is later in adolescence".

Medical intervention

Dr Dwyer told the witness that two weeks before Biddy died her killer had said to their mother that they thought about killing people all the time, had thought about killing their parents, that they had killed six chickens and had seen cat's eyes and heard voices.

The inquest heard that the mother had contacted a GP the day after XR made these comments.

Dr Dwyer asked Dr Nielssen what advice he would give parents if they were in those circumstances. He said that they should seek "urgent medical attention".

The witness was also asked what treatment XR was now receiving.

Dr Nielssen told the inquest that the person was given anti-psychotic medication and that they experienced "ongoing symptoms and behavioural problems over the next few years".

He said "[they] had a very disturbed next few years" and that they had been put on a "last-resort medication for resistant schizophrenia".

"The cause of the illness shows that it's progressed to severe and chronic form," Dr Nielssen said.

XR would have to be "medicated for the rest of [their] life", he told the inquest.

Dr Nielssen agreed with Dr Dwyer's suggestion that the inquest did not seek to "stigmatise" all people diagnosed with schizophrenia.

Under cross-examination, Dr Nielssen was asked about the actions of the GP who XR's mother had contacted before the killing.

The witness said he believed the doctor's triaging of XR, based on the information they had at the time, "was appropriate".

The hearing continues.