Decision not to consult Crown Law on whether to prosecute linked to cost-cutting.
Detectives investigating John Banks chose not to seek advice from the Government's key legal advisers over whether to charge the Act MP.
Instead, they opted to get internal advice in a move which the Police Association says could be linked to cost-cutting.
Police investigated Banks - who said this week he will give up his seat in Parliament on Friday - in 2012 over donations to his 2010 mayoral campaign but decided against prosecuting. It took crusading litigator Graham McCready to wrestle his private prosecution through the courts and force the matter to trial.
But the case cost taxpayers regardless - new information shows $44,810 was paid to the lawyer who took it through trial after taking over the case in November. He was assisted by Crown Law staff who did 557 hours of work on the case.
It also shows the majority of the Crown Law Office's involvement in the case did not come until this year and that there was no work on the case in 2012 - the time when police originally investigated.
A spokeswoman for the Crown Law Office told the Herald: "Please note that Crown Law was never consulted by the police on the decision not to prosecute. Neither Crown Law nor the Solicitor-General were asked for advice by the police in relation to this matter."
The police executive summary for the original investigation - which produced the material eventually used to find Banks guilty - stated the investigating officer's view and asked that the file be reviewed by the internal legal section.
Police Association president Greg O'Connor said the Crown Law Office would generally be called on for advice in complicated or high-profile cases.
He said "fiscal constraints" meant more careful decision-making around what material was externally reviewed.
"In a constrained financial environment all decisions are scrutinised."
He said the Banks case would lead to a change in police practice in handling political complaints. "The general feeling is these things are political spats." Politicians may now understand that "the environment has changed", he said.
"Be careful what you wish for."
Police have refused to comment on their role in the case until after Banks is sentenced on August 1.
Q & A - The prosecution
What is the Crown Law Office?
It is the nation's central legal office and gives advice and represents the Government "particularly in the areas of criminal, public and administrative law".
Do the police seek its advice?
On complex, difficult or otherwise gnarly cases, the Crown Law Office is regularly consulted.
But wasn't it a private prosecution?
It was - until Graham McCready couldn't go on. He had sought help from the Crown Law Office. Once a District Court judge decided there was a case to answer, it took over the case.
What did it cost?
Crown Law Office figures show an external lawyer has so far been paid $44,810 and its own in-house lawyer worked 557 hours.