Christopher Wayne Patterson (51) was jailed for life in 2008 for the killing of 18-year-old Michael Hutchings, whose body was found dumped in the Clutha River.
When the prisoner appeared before the Parole Board for the first time at the end of 2020, he gave an "incoherent" account of the crime.
He claimed the son of a gang member had been hurt in a car crash and that somehow killing Mr Hutchings would help him avoid retribution.
When Patterson saw the board in August he revised that version.
"He told us that he had been very angry following serious allegations made some months earlier by a babysitter," panel convener Neville Trendle said.
"The day of his offending he had been angry. He wanted to hurt someone.
‘‘He had also returned to using a mixture of Ritalin, alcohol, and cannabis. That, he told us, led him to a rabbit hole and to the ‘old insanities returning’."
Patterson accepted there was no rational explanation for the murder, but said it "reflected his beliefs at the time".
Mr Hutchings was killed on the evening of January 7, 2008, after a stab wound in his right side passed through his liver, causing fatal bleeding.
There was also a less serious wound to the victim’s neck and an injury to his hand which suggested a struggle had taken place.
The body was wrapped in a mattress protector, left in the house for almost 24 hours and then moved to the Clutha River, where it was weighted down with two metal bars, each weighing 51 kg.
Patterson’s partner Nichole Field, a former nurse aide, admitted a charge of being an accessory and was jailed for two years.
The Parole Board heard Patterson had graduated from a treatment programme for sexual and violent offenders and was now living in a self-care unit at Christchurch Men’s Prison.
He had been working in a piggery outside the wire and had been approved for the release to work scheme — allowing minimum security prisoners to undertake paid employment in the community.
Mr Hutchings’ family was vehemently opposed to Patterson’s release and outlined for the board the "profound impact" the crime had had.
The murderer apologised for his actions during the hearing and said the therapy he had undertaken while behind bars had changed his thinking.
It was not enough to convince the board that parole should be granted.
"The board is left with a picture that does not present a coherent or rational basis for his actions," Mr Trendle said.
"It does not seem to us that a clearer understanding of why he killed Mr Hutchings is likely to emerge."
He said Patterson would need treatment for his substance-abuse issues before he could be released.
The next hearing will take place in August 2023.
