While it was a "significant breach of trust", Mr Mansfield said the starting point of five years and six months adopted by Justice Kit Toogood for the computer access as the lead charge in sentencing Sarah was too high.
There were no other comparable cases in New Zealand, said Mr Mansfield, who pointed the three Court of Appeal justices to similar prosecutions in the United Kingdom.
Based on those judgments, Mr Mansfield said the starting point should have been no higher than 2 years and six months.
He also argued that Sarah should have received a cumulative sentence of 18 months for the drug supply charges, as although his offending was "hypocritical" as a police prosecutor, the methamphetamine was heavily cut. ESR testing showed the methamphetamine was only 5 per cent pure - it's normally 70 per cent pure.
Once reductions for Sarah's early admission of guilt and other mitigating factors were taken into account, Mr Mansfield said his client would be eligible for home detention.
The Court of Appeal has reserved its decision.
In an interview with the Herald before he was sent to jail, Sarah claimed that seeing a woman set herself on fire after he successfully opposed bail for her partner had triggered nightmares so intense he didn't want to sleep. And that quickly led to consuming and then dealing drugs.
"I didn't wake up one morning and decide to give the middle finger to the law," he said. "There was a set of circumstances where I was vulnerable ... but I can't blame that - I was still able to make decisions."