He shot the deer from his boat.
"It was not the king hit that he hoped for, but rather mortally wounded it," Judge Morris said, summarising the defence.
"As a hunter, he was conscious of his obligation to dispatch the animal humanely, but was also motivated by wanting the deer."
Stewart pursued the stag 500m onto Ngamatea Station land, where he finished it off with a close-range bullet.
The Wild Animal Control Act 1977 states the Crown owns wild animals until the moment they are killed, either by the property owner or by a person who has the owner's permission to hunt.
Once killed, the ownership of the deer is conferred to the hunter.
Illegal hunting carries a maximum penalty of two years' imprisonment and $100,000 fine in New Zealand.
Morris said a highly publicised penalty would make the court's stance on poaching clear and "send a strong message of deterrence".
She said if Stewart were found to be marauding Ngamatea Station when other hunting parties were present, "I think the time has come to send that message".
"However, that was not the case. Mr Stewart did not intend from the outset to go onto the property."
She said the unusual circumstances of the poaching swung the balance in Stewart's favour.
Morris said it would be "extremely unwise" for him to attempt to shoot a deer in a river again.
She adjourned the sentencing until reparation for the stag could be decided upon.
Hawke's Bay's Ngamatea Station called the ruling a "poor decision" and "a missed opportunity", while Federated Farmers said the decision did not reflect the seriousness of the crime.
Ngamatea Station deer hunting operator Bruce Bates said people roaming farms with firearms was "incredibly dangerous" and considered the incident with Stewart "a near miss".
He said he "absolutely did not accept" his defence that he unintentionally poached the stag.
Bates, who has run hunting parties from Ngamatea Station for the past 25 years, said it was immaterial whether Stewart set foot on Ngamatea land.
"He shot the deer in the river, and we own the middle of the river. But that's the judge's prerogative."
He said the value of the deer was also not up for debate, with $7500 the typical price tag for a hunting package.
"If he didn't want to pay that amount, he should have poached somewhere else."
Bates said poaching was a huge problem in the area, and the station lost $50,000-$60,000 a year.
In addition to the financial burden was the real risk of encountering armed poachers.
"We've had two occasions in recent times where we've had firearms pointed at us, and our guides have been assaulted.
"Police are hamstrung a bit by the law, it's been strengthened in recent years, but in rural areas, they're still over an hour away. We were just lucky two of our neighbours saw it happen."
Federated Farmers Hawke's Bay provincial president Jim Galloway said police had prosecuted the Ngamatea incident well, but the decision was underwhelming.
He said the basic fact remained that someone with a high-powered rifle was on a farmer's property without permission.
"Our children could be out there, our stock is there, and accidents happen.
"It's far more nefarious than people think.
"You're a long way from police, and you don't want people taking the law into their own hands."
- Wairarapa Times Age
