CAMPBELLTON, N.B. -- A jury has found a New Brunswick man not guilty of criminal negligence causing death after his African rock python escaped its enclosure and killed two young boys three years ago.

Four-year-old Noah Barthe and Connor Barthe, 6, died during a sleepover in Jean-Claude Savoie's apartment in August 2013.

The python escaped by travelling through a ventilation duct and dropping into the living room where the boys slept. A pathologist who performed autopsies on the boys said they died of asphyxiation and each was covered in puncture wounds from snake bites.

Savoie and his relatives wept in court as the verdict was delivered Wednesday night, eight hours after the jury began its deliberations.

Savoie, 40, declined comment as he left the court, but defence lawyer Leslie Matchim said his client was relieved.

"It's been quite a roller coaster road for him to have been implicated in this matter, investigated and at one point told that there would be no charges," he said.

Matchim said an investigation by the RCMP and two subsequent reviews concluded that charges were not appropriate. He said he received that assurance in writing.

The lawyer said a new lead investigator was then appointed and suddenly is client found himself facing a charge.

He said Wednesday's verdict is ultimate vindication for his client.

"This tragedy took a tremendous toll on him. He was really like family to those two victim boys and that is something that he absolutely has to carry for the rest of his life," Matchim said.

Mandy Trecartin, the boys' mother, showed little emotion and declined comment as she left the court Wednesday night.

Crown prosecutor Pierre Roussel said the family was disappointed with the verdict, but said it's too soon to consider whether to appeal.

In his charge to the jury Wednesday, Judge Fred Ferguson said that the Crown must have proven "three essential ingredients" in order for them to convict Savoie of criminal negligence causing death:

- That Savoie, "as the only adult in his residence that night," had a duty to protect the brothers, and that he failed that duty.

- That he "showed wanton and reckless disregard for the lives and safety" of the boys.

- And that his failure to take "reasonably appropriate measures to care for or protect Connor and Noah Barthe" contributed significantly to their death.

"If Crown counsel fails to prove any one of these three essential ingredients beyond a reasonable doubt, you must find Jean-Claude Savoie not-guilty of criminal negligence causing death," the judge said.

The boys had spent the day of the sleepover petting animals and playing at a farm owned by Savoie's father. Bob Johnson, the now-retired former curator of reptiles and amphibians at the Toronto Zoo, testified at Savoie's trial that snakes become more aggressive when they detect possible sources of food -- and an attack would have been unlikely had there been no animal smells on the boys.

"Those boys could have been a stimulant to that snake," he said.

A number of witnesses testified during Savoie's trial that it was common to see the cover of the vent on the enclosure's floor, and the court heard the snake nearly escaped a matter of weeks before the boys' death, but got stuck in the ventilation pipe.

Savoie's lawyer told the jury in his opening statement that Savoie believed the snake was too big get through the duct, so he didn't see a need to secure the opening.

Savoie, he said, was clearly wrong.

"Being wrong isn't necessarily criminal negligence," said Matchim.

In his testimony, Johnson said any snake enclosures for the Toronto Zoo would have a system of double doors and any openings would be securely caged. The enclosure in Savoie's apartment had a "dryer vent" style of cover for the ventilation duct that was not secured with screws or tape, he said.

Johnson said the enclosure lacked items such as rocks and branches to stimulate the python.

"I would not say that is very conducive to the well-being of the snake," he said.

A veterinarian who conducted the necropsy on the snake testified it appeared the snake hadn't fed in at least 24 hours.

Johnson said once a snake bites, it is very difficult to unlock that bite, and the large snake could have coiled around both boys at once.

He responded to the earlier testimony of RCMP officers about the python's aggressive behaviour after it was captured -- hissing and lunging at the glass of the enclosure.

"A snake that responds like that is a very aggressive snake," he said. "It was an extreme response to human presence. This animal was dangerous."