Amanda Banks' "obsessive" detective work saw her husband John Banks' electoral fraud conviction quashed yesterday and answered a High Court judge's doubts over her honesty.
But the case has taken a toll on their marriage and the couple now live at opposite ends of the country as a result.
The Court of Appeal yesterday overturned former Act leader Mr Banks' conviction for filing a false electoral return, charges which ended his parliamentary career.
A jubilant Mr Banks paid tribute to his wife who he said had been a hero for her part in clearing his name.
Mr Banks was convicted in the High Court this year after failing to disclose donations from Kim Dotcom to his Auckland Mayoralty campaign in 2010.
Crucially, the High Court's Justice Edwin Wylie believed testimony given by Dotcom's wife Mona over that of Mrs Banks about what was said at a lunch where both were present and at which Dotcom said donations were discussed.
Mr Banks' appeal introduced affidavits from two US-based businessmen who he says were at that lunch. The pair - David Schaeffer and Jeffrey Karnes - both said donations were not discussed at that lunch.
The Court of Appeal's Justices Ellen France, John Wild and Forrest Miller said that if the new evidence had been accepted in the High Court trial "it likely would have changed the outcome". The Court of Appeal's decision notes that Mrs Banks "was stung by the judge's opinion of her reliability".
Amanda Banks: Her research paid off.
"She became quite obsessed, as she puts it, with identifying the two Americans.
"She recalled that a transpacific communications cable had been discussed at the lunch and scoured news articles on the topic, eventually finding one which mentioned that Mr Dotcom had endorsed such a project and was trying to organise a group of investors to fund it."
Mrs Banks' research also identified the second businessman and Mr Banks' lawyers contacted the two men and secured sworn affidavits from them.
"Amanda was humiliated in the High Court," Mr Banks told reporters yesterday. "Instead of leaving with her tail between her legs ... she set out to find the witnesses who would dismantle the evidence of the Crown case. She spent a lot of time on that and she found those witnesses and we tracked them down to the United States and they stepped up to the plate and swore those affidavits. She's been a hero in all of this, and she put up with a lot."
However, the Weekend Herald understands the strain of the case on the Banks' marriage is a key reason why the couple now live apart, with Mr Banks in Auckland and Mrs Banks moving to Alexandra in Central Otago. It is understood the couple are on amicable terms.
Mrs Banks was yesterday unwilling to comment on the decision other than to say she was pleased her work had paid off.
"Yes, I am pleased. It is a good news story. It's great, it's good for John."
Watch John Banks on his "three-year nightmare" tinyurl.com/ng3m6yv.