A former licensed Bay of Plenty retailer of synthetic cannabis has been jailed for three years and four months.

David Ronald Young, 52, was arrested after a series of police raids netted $181,000 in cash and drugs with a street value of more than $1 million.

David Ronald Young. Photo: Benn Bathgrate.

Young appeared in Rotorua District Court on Wednesday, where he was sentenced on charges of possession and supply of synthetic cannabis and the class C drugs TFMPP and BZP.

Judge Philip Cooper says the case involved "very large quantities [of drugs] with very large returns".

Young, the owner of Rotorua retailer Skingraft, was formerly licensed to sell synthetic cannabis until the law change on May 8, 2014, which made the sale of the product illegal.

Police executed a number of search warrants on storage premises in September and October last year, uncovering 57kg of herbal material, 16.12 kg of pre-packaged synthetic cannabis, 6000 bags/tins of synthetic cannabis, 251g of TFMPP and 2.9g of BZP.

The court was told that a further search of Young's home and car uncovered $181,000 in cash.

Police estimated that the 57kg of 'herbal material”, once manufactured into synthetic cannabis, would have a street value of $1.1 million and that the pre-packaged synthetic cannabis would have a street value of between $230,000 and $320,000.

The combined TFMPP and BZP was valued at between $34,000 and $89,000.

A blender was also found at the storage units which, in text messages intercepted by police, was described by Young as 'the blender from 'Nam”.

Young's lawyer, Martin Hine, says since his arrest, Young had taken a drug and alcohol course and gained a new insight into the effects of synthetic cannabis.

'Retailers often didn't see the ravages the drug imposed on users,” he says.

'For him it has been a steep learning curve.”

Hine said that up until his arrest, Young had been a good citizen and said the impact of his arrest on his family had been dramatic.

He said that this was the first time in 32 years of marriage that Young and his wife, who visibly upset in court, have been separated.

Hine also claims the synthetic cannabis the police found had been acquired legally before the May 8 law change, and that Young was storing it in anticipation of a later law change to make its sale legal again – an argument Crown Prosecutor Amanda Gordon rejected.

'The covert searches by police indicated new product appearing on each occasion,” she says.

'The product amount was increasing. Further material was being brought into the storage shed.”

Gordon says the haul of products included Karma, which had been recalled in January, and Hindu Kush, which Gordon said had never been approved for sale by the Department of Health.

She also said the amount of drugs, the blender and a stash of bags presented 'clear evidence of the defendant manufacturing”.

In his summation, the judge described the offending as 'a very significant commercial exercise”.

'This wasn't a case of you trying to get rid of product you had left when the law changed,” he says.