The mayor of London, Ont., forged a document he submitted to the House of Commons for expenses while he was a Liberal cabinet minister and abused the public trust, a judge said Friday in finding the former MP guilty on three fraud-related charges.

Fontana took a contract from a deposit on his son's wedding and altered it to make it look like it was for an MP event at the same venue, then tried to get the $1,700 reimbursed, Superior Court Judge Bruce Thomas found.

His "criminal activity" was only detected when the $1,700 ended up being sent to the venue instead of Fontana personally, then at that point he could hardly ask that the cheque be reissued, Thomas found.

Story continues below advertisement

"While I am perplexed as to why a man of such accomplishments might choose to take these actions for $1,700, I do not find that that detracts from the strength of the Crown case," he said in his decision.

"I have long ago abandoned the notion that motive results from a logical cost-benefit analysis."

Fontana sat passively as the judge pronounced his convictions, then got up and hugged his wife.

"I'm very surprised, shocked, devastated by obviously the verdict," Fontana said outside court.

He did not say what the convictions mean for his political future nor if he would appeal.

"I regret that all this had to happen, especially for the people of London, but I'll have something to say in the near future," he said. "I obviously need to digest what has taken place, talk to my legal team and look at what I'm going to do."

Fontana testified during the trial that it was "stupid" of him to alter the document, but he insisted it was no forgery.

Story continues below advertisement

He admitted making seven changes – including whiting out his wife's signature, replacing it with his own and writing the word original in quotation marks at the top – to an existing contract with the Marconi Club for his son's 2005 wedding to reflect an event he planned for then finance minister Ralph Goodale at the same venue.

Other alterations on the contract were changing the date of the event from June 25, 2005, to Feb. 25, 2004, the word "wedding" to "reception" and the addition of a yellow sticky note saying "misc constituents reception."

The event didn't end up going ahead at the Marconi Club, but Fontana testified he believed the club was owed a $1,700 deposit from his MP budget. Since he had only spoken with the club's president over the phone and didn't have any paperwork, Fontana changed several details on the wedding contract from a few months prior and submitted it, he testified.

The president of the Marconi Club, a friend of Fontana's for more than 40 years, testified for the defence and backed up Fontana's story, but the judge pointed to various inconsistencies and said Vince Trovato's story "does not hold together."

"When he testified I got the feeling that Mr. Trovato was making it up as he went along," Thomas found.

"I come to the conclusion that he and Mr. Trovato either collectively or individually concocted a story for this court that was intended to create a reasonable doubt and in doing so allow Mr. Fontana to escape conviction. In my view any doubt raised in these circumstances would have to be far-fetched and fanciful and defy common sense."

Story continues below advertisement

Fontana is to be sentenced July 15.