Banks was yesterday found guilty of filing a false return in relation to the donations, which were subsequently declared as anonymous. He could face a jail sentence of up to two years or a $10,000 fine.
In his judgment, Justice Wylie refused to accept Mrs Banks' testimony. He said he "did not consider Mrs Banks to be a reliable witness" in relation to events that transpired at the Dotcom Mansion.
Mrs Dotcom, in contrast, was "reliable and credible".
Mr Dotcom had batted away claims that he could control his wife's testimony by saying they were separated.
Yesterday, Mr Dotcom said the verdict settled any questions of credibility that arose during a court session in which Banks' lawyer, David Jones, QC, attacked the businessman's honesty.
"He called me a liar 52 times," said Mr Dotcom. "I was not treated as a witness, I was treated as an accused. I was called dishonest, was called a liar, was called a criminal. That was unfair.
"I'm glad this judgment and the words of this judge reflect the truth - that our witness statements were reliable, that this label of liar ... now has to be applied to his client and not me, my family and my former staff."
Watch: Banks and Dotcom at Court
Mr Dotcom and his former security chief Wayne Tempero were also described as "reliable and credible witnesses". Justice Wylie said Mr Dotcom "in particular was, in my view, a good witness".
Mr Dotcom said the verdict raised questions about why police did not prosecute Mr Banks.
"Clearly there was something wrong in that decision-making process. It took a retired accountant in a private prosecution to get to this point."
He said the verdict also raised questions about Prime Minister John Key's support of Banks throughout the case. "He certainly looks like a fool when you look at this judgment now. His judgment was obviously wrong, just like the police."
Mr Dotcom spoke of Banks' rejection of him following the FBI-inspired police raid on his mansion in 2012, when he was arrested for mass copyright violation.
"He called me a friend several times. Someone who says that cannot just run for the hills and duck for cover just because an allegation has been made, even though the allegation was enforced with two helicopters, 72 police and a worldwide media frenzy."
Watch: John Banks: 'I don't do bad things'
Mr Dotcom said he had no regrets over the donation. "I didn't even understand who or what John Banks stands for. I gave it to a mayor who wanted to be my friend and had tried to help me.
"To me, $50,000 was an amount I made every six hours."
Mr Banks faced charges relating to three donations - two from Mr Dotcom and one of $15,000 from SkyCity.
When delivering his decision to the packed courtroom yesterday, Justice Wylie said he was satisfied beyond reasonable doubt that Banks knew the electoral return was false when he signed it, in relation to the Megastuff payments from Mr Dotcom recorded as anonymous.
The judge couldn't, however, find Banks guilty beyond reasonable doubt about the SkyCity donation of $15,000 made in May 2010, which was listed as anonymous in the return.
Read more: John Banks remains in Parliament — for now
Banks' QC, Mr Jones, asked Justice Wylie not to enter a conviction, and indicated there would be an application for a discharge without conviction at sentencing in August.
Outside court, Banks said he was working through his legal options, but respected the judge's decision.
"We are disappointed with the verdict. We are surprised with the result," he said.
"From day one I have told you I would never, never knowingly file a false anything let alone a false return."
Banks left the High Court accompanied by former mayoral campaign team member Michelle Boag, current staff member Chris Diack and former Act MP and president John Boscawen.
The group walked across central Auckland from the court building to the Stamford Hotel, where Banks has an apartment. They drank tea in the foyer before Banks retired to his apartment.
Watch: John Banks found guilty
An adviser to Banks, speaking anonymously, said an appeal was being considered and likely to go ahead after sentencing.
He said Banks was in a positive mood and remained in strong spirit.
"From where he's come from, every day is a benefit. I think he's philosophical about it. He sees this as a process he's got to get through.
"He was certainly disappointed with the verdict — naturally disappointed.
"He's been a boxer. He looks at it in terms of boxing — 'there's a few more rounds to come'."
Retired Wellington accountant Graham McCready, who initially laid the charge as a private prosecution, said he was ecstatic with the verdict.
Banks will be sentenced on August 1.
– Additional reporting: Jimmy Ellingham
Read the verdict of Justice Wylie here:
Detention options
There's no reason John Banks couldn't serve out his sentence in luxury if sentenced to home detention.
A report on the sentencing option was called for by Justice Edwin Wylie after the Act MP was found guilty yesterday of filing a false electoral return.
The Act MP has an apartment in the residences above the Stamford Hotel (below) on Albert St, central Auckland. The $1 million apartments are described by estate agency Colliers International as "generously-sized ... luxuriously appointed and superbly finished in rich polished marbles, limestone, timbers and pure wool carpets".
Criminal Bar Association president Tony Bouchier said anywhere considered for home detention had to be able to be electronically monitored.This was done through a "bracelet" worn on the ankle, which sent a signal to a receiver in the home which only worked inside a particular radius.
Mr Bouchier said the Probation Service was responsible for assessing the suitability of a possible home-detention site. It would visit the home, see whether monitoring functioned there and then conduct interviews with others living there to make sure they had no objections.
"In many ways home detention is more restrictive [than prison] and you get less freedom." He said it could be lonely - those in prison had company, outside exercise and other possibilities which made a sentence less onerous.
Watch: Gerry Brownlee on the verdict
Key points of Justice Edwin Wylie's judgment
• "I watched the Dotcom witnesses carefully while they gave evidence. I did not notice anything in their demeanour to suggest they were not telling the truth."
• "It is reasonable to infer that Mr Banks requested that the donation be split so they did not stand out and so that the donations would be consistent with other donations of $25,000 ... "
• "The defence theory of conspiracy ignores the fact that none of the Dotcom witnesses was under Mr Dotcom's influence or control when they gave evidence."
• "Mr Banks deliberately chose not to check the return to see whether the Dotcom donations were properly disclosed because he had no real doubt as to what the answer was going to be ... he wanted to remain in ignorance."
