In March 2016 he was sentenced to nine years and nine months' imprisonment after pleading guilty to two charges of blackmail and charges of possession of drugs for supply and dealing in a class C drug.
He became eligible for parole in January last year and was denied an early release from prison on multiple occasions.
However, after a hearing in February the Parole Board deemed Kerr no longer posed an undue risk to the community.
In November 2014, Kerr mixed highly concentrated amounts of the poison with baby milk formula and posted them to the dairy co-op and to Federated Farmers, with a letter demanding the country stop using 1080 or he would release poisoned infant milk powder into the Chinese market and one unspecified market.
By March 2015, police had 36 fulltime staff on the case, resulting in a $5m bill for the taxpayer.
The court ultimately found that his objective was personal financial advantage because of his interest in promoting an alternative pest control product.
Kerr's drug offending involved possession of 32,000 pills with a street value of some $64,000.
He has previous convictions for growing and selling cannabis in 2005.
In a parole decision released to the Herald Judge Geoffrey Ellis said Kerr's underlying risks were identified as "poor problem‑solving, limited awareness of the consequences of his actions on others, risk‑taking and financial involvement, lack of support from family and inability to accept feedback".
"Mr Kerr was most recently before the Board on 9 December 2019. The board then noted that he had completed rehabilitation but was concerned that his safety plan did not adequately address potential financial pressures nor his drug dealing.
"The board expected the development of his plan, particularly regarding drug offending risks."
Judge Ellis said a new Parole Assessment Report presented to the panel last month advised that Kerr "manages himself well using skills from his psychological treatment".
"A reintegration hui was held in November and there is a positive report on the outcome of that hui in the PAR," he said.
"Mr Kerr has a very low assessed risk of re-offending and he is on a minimum security classification.
"There are no incidents or misconducts recorded during his sentence."
A police supplied picture of Kerr's blackmail letter, threatening to poison baby milk formula unless the NZ government stopped using 1080 poison. Photo / supplied
A psychological report stated Kerr's risk of re-offending was considered to be low.
"His release plan was assessed by the psychologist and was considered adequate for reintegration purposes," said Judge Ellis.
"Mr Kerr has received very positive reports on his presentation and conduct in prison."
The Principal Corrections Officer overseeing Kerr said he was "a good prisoner to have in the unit".
Judge Ellis said Kerr had no specifically‑organised employment and indicated that he would not be in a hurry to seek paid employment once released.
However, it was "apparent" that he had "independent means available to him" via a person who had independently managed his money while he was incarcerated.
He owned a home that he rented out and had "pro-social support" in the community.
"Mr Kerr was challenged as to the circumstances of his offending and the changes that have now occurred through his time in prison," said Judge Ellis.
"He stressed the difficulty of his mental state at the time of the offending and compared that with the circumstances now awaiting him on his release.
"He has an attentive and strongly pro-social partner. He has positive support from other close family members.
"He has been supported to address the personal issues affecting him at the time of his offending. He expressed strong motivation to avoid situations or associations linked to his past offending. He has financial security.
