Money was a motivation for 1080 blackmailer Jeremy Kerr the High Court has ruled.

Chief High Court judge Geoffrey Venning said financial gain from increased sales of his own rival pest control product was a factor even though Kerr didn't know how much he would gain.

Justice Venning said Kerr was under financial pressure at the time he sent letters threatening to release 1080-laced baby formula in the Chinese market and one other market unless the poison was banned.

The severity of sentence hangs on the outcome. The maximum penalty is 14 years in prison.

The 60-year-old from Mellons Bay, East Auckland, pleaded guilty in December to two counts of blackmail but did not accept the assertion his actions were motivated by money.

Justice Venning’s decision this afternoon came after a disputed facts hearing resumed to decide whether or not his offending was financially motivated.

Crown prosecutor Christine Gordon QC told the court Kerr was motivated by financial gain, as he owned a rival pesticide called Feratox, for which he received annual royalties of $100,000.

The Crown argued that he was strapped for cash, his bank accounts were at their maximums, he had extended the overdraft of his mother’s account in “questionable” circumstances, and he was struggling to pay his bills.

Kerr’s defence argued that although money was tight, that was because of spending in a company he was building called Natures Support – that makes possum fur belts for people with back problems. That spending was discretionary. Take that away and he was “comfortably off”, John Billington, QC, said. Kerr’s position would not be worsened should that company fail as he had no financial liability to it such as guarantees.

Had 1080 been abandoned as a result of Kerr’s blackmail attempts, he may have benefited in the short-term from an increased demand for Feratox.

“A small financial gain may have been the consequence but it was not the primary driver for an act of incredible stupidity and irrationality by someone who ought to know better,” Mr Billington said.

Kerr was remanded in custody for sentencing on March 23.