Wayne Church was washing dishes when he was stabbed four times with a butcher's knife in the head, neck, and back.
Justice Pheroze Jagose ruled today that William Church, 23, will be detained in hospital as a special patient after he fatally attacked his father in Pāpāmoa East in September last year while being "severely psychiatrically unwell".
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Church has treatment-resistant schizophrenia and a mental disability and was deemed unfit to stand trial in July after pleading not guilty.
However, Justice Jagose said in the High Court at Rotorua this morning he was satisfied on the balance of probabilities that Church caused his father Wayne's death [previously named as Michael Steven Church].
William Church's defence counsel Rachael Adams agreed that it was best for Church to be detained as a patient, as did Crown prosecutor Richard Jenson.
The Crown filed 29 formal statements and additional transcripts and photographic evidence.
Auckland City Hospital forensic pathologist Kilak Kesha carried out the post mortem.
She said Wayne Church's four stab wounds "all significantly penetrated the body and gave rise to associated haemorrhages".
Justice Jagose said that "transcripts of 111 calls and DVD the interview contain a myriad of admissions by Mr Church."
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Psychiatrist Dr Peter Dean concluded, "By reason of Mr Church's continuing, although improved, psychiatric illness, and lack of insight into his condition and his consequences, he continues to pose a serious risk to the safety of the public."
Psychiatrist Dr Barry Walsh said Church's illness was complicated by "fluctuating compliance and substance abuse".
They and another psychiatrist agreed Church should be a special patient.
Justice Jagose said hospital detention was the best prospect for Church's ultimate accountability for his father's death, "while providing for an additional layer of oversight of decisions affecting his status, leave, and eventual release".
William Church's mother was present at the High Court for the end of the ruling.
She declined to comment on the outcome, as did lawyer Rachael Adams.