The Court of Appeal overturned the conviction and sentence - Te Hei pleaded guilty during a second trial to an amended lesser charge of wounding with intent to injure with reckless disregard for the safety of others.
He was on Friday sentenced to just two years six months, after allowances to recognises efforts had made to turn his life around and for the late plea of guilty.
Both Judge Rea and Crown prosecutor Jo Rielly commented on the quality of a cultural report commissioned by the defence, in which the Judge said Te Hei had "bared his soul" in a way which highlighted an upbringing which left him feeling as if he had little course but to resort to violence.
It had ultimately led to almost all his adult life being spent in prison.
Rielly described the cultural report done by a Christchurch agency as "very helpful — probably the best one I've ever read".
"It's clear he now recognises he needs help and support and rehabilitation," she said. "It seems his commitment is real and honest."
"Mr Tennet, you probably wish you'd said all that yourself," said Judge Rea, to which the counsel replied: "I agree with everything that's been said."
The process had included a restorative justice meeting with the victim, but the Judge reiterated the rest, including getting out of "the gang" and taking further steps to satisfy the Parole Board is up to Te Hei, whose history of offending dates back at least to the age of 10.
It escalated with an armed bank raid in Hastings for which he was sentenced in 1993 to nine years' jail, during which he would be sentenced in 1997 to another 10 years for attempted murder after he and and his brother attacked a fellow inmate in maximum security prison Paremoremo, including 10 stab wounds with a pair of scissors.
Released on parole in 2011,Te Hei lived with a partner and children and was regarded as having made good progress, until a 2014 machete attack on a woman in Gisborne, leading to the 2016 first sentence of preventive detention, with a minimum non-parole period of five-years.
It is however an indeterminate sentence in which offenders can be paroled, on conditions enabling them to be recalled in the event of further offending.