"There appears to be significant insight now, brought about by the consequences of his conduct. The court can be confident he will not be here again."
But Justice Geoffrey Venning was sceptical, noting that Kerr tried to minimise his behaviour in pre-sentence interviews.
"I have some doubt, frankly, whether you're truly remorseful," he said.
The judge said the offending was clearly for commercial gain.
"Mr Kerr, you're a businessman, you took a business risk in becoming involved in dealing drugs in this way. You were caught," he said.
Police searches at his Contimo business address in Highbrook and at an East Tamaki storage unit in November 2011 uncovered 32,000 pills, which could have sold for up to $40, possibly netting Kerr as much as $1,280,000.
But he later told officers he had only been selling the tablets at $2 a pop.
He came to the police's attention when they followed another person of interest to a South Auckland cafe who met Kerr.
Covert searches of his storage unit in September 2011 found "a variety of pills, powders, pill dyes for pressing pills with a variety of logos such as are commonly found on ecstasy tablets, and other paraphernalia for pill pressing", the Crown said.
Kerr told police he had the BZP powder left over from when it was legal in 2005 and had been "trying to get rid of for a long time".
His blackmail case was labelled "near the most serious case of its kind" by Justice Venning in March, after the court heard it cost the country more than $37 million.
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.
Kerr initially denied involvement when interviewed by police but later confessed when DNA evidence proved he had written the threat letters.
The Herald also revealed that in 2004 Kerr was convicted on charges arising from an elaborate hydroponics cannabis operation concealed in a rented East Tamaki warehouse.
Police found a hydroponics cannabis operation of 450 plants with an estimated street value of $150,000 hidden inside premises he also used for his pest control business.
The plants were inside shipping containers equipped with extraction fans, ultra-violet lighting and watering systems.
Most of the factory was boarded off to conceal the cannabis operation, police said at the time.
Kerr will celebrate his 61st birthday behind bars on Wednesday.
