McMahon would contact rabbit owners or breeders online and, under a cloud of meth, sneak into their backyards at night to steal the animals from their cages and hutches.
After 18 months of offending, McMahon was arrested and by mid-2017 was before Auckland's courts.
Judge Eddie Paul was the first to hear the case in his courtroom and also deal with the issue of suppression.
"Counsel have been somewhat silent about public interest and the media's right to fairly report proceedings," he said.
"There must be a significant public interest where a person targets pet animals for their own particular interests.
"Clearly, there is media interest in this alleged offending. Oftentimes, offending comes before the court that is of significant interest to the media, may well be distasteful but defendants, on that basis alone, cannot be justified in having orders continue in their favour."
Judge Paul declined to make an order suppressing the rabbit thief's name, but that was just the beginning of the saga.
McMahon would appeal Judge Paul's decision to the High Court - automatically imposing an interim suppression order.
In July 2017, Justice Graham Lang heard the challenge.
"The case against Mr McMahon has some unusual features," he commented.
Ultimately, he agreed with Judge Paul and dismissed the appeal, saying he did not accept publication of McMahon's name or the charges he faced would prejudice a trial.
"On their face, they are straightforward charges of burglary," he said. "None of the charges refers to the unusual object of the alleged offending, namely small animals."
Fergus McMahon, then known as Brendan Francis McMahon, pictured on his mobile phone outside a courthouse in Sydney in 2005. Photo / Getty Images
In 2006 and then known as Brendan Francis McMahon, he was jailed and later acquitted on mental illness grounds for what was described as "one of the worst case scenarios of aggravated cruelty to animals" in Australia.
During the mid-2000s, McMahon had been arrested after dead or dying animals - some of which had been skinned - were found in and around his downtown Sydney office.
The allegations against him included the torture and mutilation of 17 rabbits and a guinea pig.
He also faced a charge of bestiality, but this was later withdrawn.
Justice Lang ordered the summary of McMahon's Auckland offending to remain suppressed but only if he decided to go to trial.
Many months and several District Court hearings followed but McMahon never went to trial, instead he pleaded guilty in 2018.
Despite this, the suppression order continued and was not reviewed again until McMahon was sentenced in May this year.
Lily the stolen Netherland Dwarf. Photo / Supplied
At sentencing McMahon's lawyer asked the court to permanently suppress the entire case.
Despite opposition by the Herald and police, Judge Ema Aitken granted the application.
"I am satisfied that the allegations of offending in Australia lend themselves to considerable sensationalisation by the media and public alike and that there is a very real risk that not all media outlets will make it clear that the defendant was found not guilty by reason of mental illness - in other words, that he was not legally responsible for the offending," she said.
"Instead there is a very real chance that his past behaviours and his current behaviours will become conflated and a rather prurient interest taken in this defendant with the drawing of unfounded assumptions as to the current offending for which he appeared for sentence."
Judge Aitken said McMahon, who was described as a "vulnerable" person, would suffer "an unsettling and adverse impact" on his health if publication was allowed.
She said a story by the Herald could also cause a "real risk of relapse in the face of such publicity" despite McMahon seeking treatment for his drug dependency.
"Those people are not immune to the impacts of sensational reporting and there is, in my view, a very real chance that some of his support may fall away should these matters be publicised.
"I am satisfied that the real public interest being advanced here is an interest in the more salacious and prurient detail that attached to the offending in Australia rather than the unusual but more bland facts that relate to this offending."
Judge Ema Aitken suppressed the case and was concerned it would lead to "considerable sensationalisation by the media and public". Photo / Dean Purcell
Judge Aitken ordered that publishing any parts of the evidence, the court's sentencing notes, the summary of facts, both counsels' submissions, the probation report and victim impact statements was "forbidden".
The Herald, however, appealed the order - taking the case back to the High Court.
Acting as counsel for the Herald, Robert Stewart argued the court "cannot enter into assessment of whether media or public interest is appropriate or 'undue'."
"The right to receive and impart information is not limited in the present context according to qualitative and subjective standards adopted by the judge," he said.
Justice Grant Powell, who heard the appeal, agreed with the Herald and said there is a "very obvious and genuine public interest in this story".
"Given Mr McMahon has now received considerable and ongoing treatment for these issues it is impossible to conclude, in the absence of a comprehensive and up-to-date assessment to the contrary and following completion of his rehabilitation, that there is any real and appreciable risk to Mr McMahon's safety if the details of the New Zealand offending are published," he said.
The judge revoked the permanent suppression order and made his final judgment in the case last Friday.
Yesterday, the Herald on Sunday finally revealed McMahon's case.
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