Kingi plead guilty to the Australian charge and at the time no questions were raised about his mental state, but subsequent assessments in New Zealand following the killing of Mr Taniora indicated he was most likely mentally impaired at the time of his wife's death.
"I am more than satisfied the Mr Kingi's psychiatric illness is deep-seated and longstanding. It led to the tragic death of Mr Taniora and may well have been instrumental in the tragic death of Donna Kingi in 1997," Justice Toogood said.
"I am in no doubt that the continued detention of Mr Kingi is necessary for the protection of members of the public and other members of Mr Kingi's whanau."
He described it as a tragic case and while Kingi might improve enough to stand trial, it was not possible to say when that might happen. While detained in hospital he would undergo mandatory reviews every six months.
The court heard how Kingi denied he was mentally unwell nor would he contemplate a defence claiming he was insane at the time. He would instead plead self-defence or guilty to the manslaughter of Mr Taniora.
Kingi told expert doctors he believed his family had conspired against him to steal his land.
When his father died in 2004 each of the 10 siblings were left equal shares in the block of land at Ngararatunua. In 2016 five of the siblings were living on the land and Kingi lived in a tent towards the rear of the land but had said he wanted to build. He had become increasingly dissatisfied with his living situation.
Kingi also had delusional beliefs. He thought he could continue to work on a cure for DNA poisoning and possibly cancer.
He also had ideas about certain helicopter parts and software for computers that he believed would be of interest to security agencies, such as the Pentagon.
Kingi wanted to go to jail and not be held as a special patient. However, specialist doctors recommended Kingi be detained, as that would be the best way to deal with his treatment-resistant paranoid schizophrenia.
In sentencing notes from the Supreme Court of New South Wales, obtained by the Northern Advocate, it reports that at the time of the murder Kingi had recently separated from his wife, Donna, who had married in April 1996. They became embroiled in an argument over the custody of their daughter.
Kingi left, went to his house where he got a knife and a crowbar and returned. He hit her over the head with the crowbar and stabbed her repeatedly in the chest causing her immediate death.
Kingi drove away with his daughter. However, realising the enormity of what he had done he dropped the child at his brother's home and gave himself up to police and admitted what he had done.
The Australian judge's notes said that Kingi's prospects of rehabilitation were good.
"There is no suggestion that he is a danger to society in the future, and I think it most unlikely that he would offend again in any significant way."
He appeared to be have used his time in prison productively and engaging in educational courses, which included those in communication.
The judge noted: "If he remains in this country upon his release, life is likely to be fairly bleak. Most of his family is still in New Zealand and the familial relationships which he developed in this country have been shattered by his own act of violence."
The Judge said Kingi would need help and guidance for a considerable time to come to terms with the difficulties he would face.