A man who sent an email to Prime Minister Jacinda Ardern threatening to "personally wipe you off this f***ing planet" has been sentenced to one year in prison, eight months after a jury found him guilty. 

Wearing all black, Michael Cruickshank, 56, rocked on the balls of his feet in Auckland District Court today as he stood before Judge Brooke Gibson, who explained why Cruickshank wouldn't be a good candidate for home detention. 

"You have a complete lack of insight. You have a high sense of entitlement," the judge said, citing reports prepared for the sentencing hearing. "You simply don't recognise acceptable boundaries." 

During Cruickshank's trial in July, Crown prosecutor Dennis Dow said the defendant sent around 88 lengthy emails to government officials and agencies in a four-month period between October 2019 and January 2020. He regularly referred to Ardern and the Government as criminals, slave traders and state-sanctioned terrorists, but it was two emails in particular that went a step too far, threatening violence, Dow said. 

The emails were sent 30 minutes apart on January 20, 2020. 

"If you continue to support state terrorism ... and declare act of war on my life ... I will personally wipe you off this f***ing planet," read the first email, which was sent to Ardern, ACC staff, the media and others. 

"I will blow your ... head off if your gas lighting on my life continues," he added 30 minutes later in an email sent to both Ardern and fellow Labour MP Andrew Little. 

"You have kids who want to see you grow old, as do I," the email continued. "I suggest you place that into proper perspective." 

Cruickshank was arrested three days later on three counts of threatening to kill, after police carried out a search warrant at his Auckland home. 

He had already been well known to a staffer at the PM's office tasked with vetting correspondence. She testified she first came across his "usually angry but not threatening" emails during Helen Clark's tenure. 

Judge Gibson noted today that Cruickshank's sentencing hearing was significantly delayed both due to Auckland's Covid-19 outbreaks and so that a psychological report could be prepared ahead of his sentencing. 

The report found that although Cruickshank had interacted with mental health workers over the years, he suffers no serious mental illness. 

Gibson also pointed to Cruickshank's indication at trial that he was intoxicated and had no memory of writing the letters. Intoxication is not a defence, the judge noted. 

Defence counsel Marek Hamlin asked the judge to consider a sentence that avoided prison, but the Crown said the need for deterrence was important and the judge ultimately agreed. 

"Public officials are very much at risk of this kind of offending and the court needs to respond accordingly," Gibson said, describing the offence as one that "strikes at the roots of our democracy". 

Cruickshank was a labourer who immigrated to New Zealand from Northern Ireland in the 1990s. After suffering an accident in 1995, he was unsatisfied with the support he received from ACC. That anger lingered for decades and manifested itself in "a relentless campaign of emails", the judge noted. 

Gibson described the emails as "written in a grandiose and inarticulate way" but threatening nonetheless. 

"You feel persecuted and you have made repeated threats to people in the past," the judge said, assessing him as a continued risk of re-offending. "The starting point has to be a sentence of prison."