Yet in the four decades after he wed his first wife in New Zealand, the 70-year-old said he never twigged the pair might still be married, despite the fact he never signed any divorce papers.

The past caught up with Stevenson when he was found guilty of bigamy in the ACT Magistrate's Court on Monday.

The court heard he ''chose to put all of New Zealand behind me'' when he left his first wife, whom he married in 1962, and their three children and came to Australia in 1970, later becoming a priest with the Liberal Catholic Church, which does not enforce celibacy.

Read more: Priest facing bigamy charges in ACT court.

He re-married in 1974 and, after that marriage ended in divorce, wed his third wife in 2002.

Stevenson never told his second and third wives he had been married before, or that he had any children, the court heard.

He argued his actions were an honest or reasonable mistake, which is a defence against the federal charges of bigamy.

The court heard Stevenson partly believed his marriage was over because a New Zealand police officer in the 1970s had told him: "She's going to divorce you."

Stevenson told the court he assumed his first wife had taken care of the divorce, despite the fact he never received any paper work, and that there would have been appropriate ''checks and balances'' before he remarried in Australia.

The court heard his first wife had never applied for a divorce because she couldn't afford it.

Prosecutor Katrina Musgrove argued Stevenson's beliefs that his first marriage had ended were not based on fact.

Ms Musgrove said he had completed a half-day training course on the Marriage Act and had officiated at three weddings when he was a priest.

She said Stevenson never spoke about his first marriage to his second and third wives, and had given two of his daughters – each born to different mothers – the same first and middle names.

The court also heard the defendant had ticked "bachelor" rather than "divorcee" on legal documents before his second marriage.

Stevenson, who represented himself, said he ''had the honest belief that things would be done'' to end his first marriage, but that had been a mistake.

''All I stand for is gone and I really have to accept responsibility for my actions.''

Magistrate Beth Campbell said it ''beggared belief'' that Stevenson wouldn't understand that the same formalities and documentation required to legalise a marriage would not be required to end one.

She doubted he really believed his marriage was over due to a ''flimsy, one-sentence line'' from a police officer.

Ms Campbell said Stevenson's failure to disclose correctly his marital status on official documents and the fact he gave two of his daughters the same names showed he had no intention of revealing his first wife and children to his subsequent partners.

She said Stevenson's defence could be encapsulated by his earlier comment that he ''chose to put New Zealand behind me''.

Ms Campbell said she suspected that was the reason Stevenson didn't reveal his first marriage to his most recent spouses.

''This was an unhappy part of his existence and he chose to believe if he ignored it, it would all disappear,'' Ms Campbell said.

Ms Campbell was satisfied each offence had been proved beyond reasonable doubt.

Stevenson will be sentenced on August 5.