CAMPBELLTON, N.B. -- An escaped python coiled itself around two young boys, strangling them and biting them repeatedly, a pathologist told the trial of the snake's owner Thursday.

"Most of the puncture wounds were found on the face," Dr. Marek Godlewski testified Thursday about injuries to Connor Barthe, 6, at the criminal negligence trial of Jean-Claude Savoie in Campbellton, N.B.

Godlewski conducted autopsies on both Connor and his four-year-old brother, Noah, on Aug 6, 2013, a day after the snake killed them during a sleepover with Savoie's son. He described each autopsy separately Thursday.

Godlewski found Connor suffered multiple puncture wounds, abrasions and bruises, as well as hemorrhages in his neck muscles, while Noah had multiple puncture wounds compatible with bites over his body. He says there was blood on Noah's upper body.

Godlewski said the puncture wounds to Connor were consistent with snake bites.

"I do agree the pattern of the wounds (were) consistent with the pattern of the teeth of this snake," he testified.

The boys died as a result of the snake "coiling" around them, he said, with the specific cause of death being "asphyxia due to neck strangulation."

There was evidence of "coiling" around Noah's chest and neck, as well as marks on his face and nose, he said.

Savoie's African rock python had escaped its enclosure. It's believed the snake travelled through a ventilation duct and fell into the living room where the boys were sleeping. Savoie's own son, who was sleeping in a different room, was unharmed.

Earlier Thursday, John O'Brien, the boyfriend of the boys' mother, testified he had noticed the cover for the ventilation duct on the floor of the python's enclosure on several visits to the apartment -- as recently as the week before the boys' death.

The apartment was above a reptile store owned by Savoie.

The boys' mother, Mandy Trecartin, lived next door to Savoie, and O'Brien said he came over the morning of the tragedy, pounded the door and shouted: "Oh my God, the kids are dead."

O'Brien said he went to Savoie's apartment, and found Trecartin's sons dead on the floor.

"I checked for a pulse but there wasn't anything. They were blue," he testified.

Dr. James Goltz, the chief provincial veterinarian for New Brunswick, testified Thursday he saw nothing abnormal with the snake when he conducted a necropsy a day after the tragedy.

He said its stomach was empty, indicating it hadn't eaten for at least a day. He also described how a python can change its diameter by contracting -- an issue that has come up during the trial because its resting width appeared larger than the duct it apparently escaped through.

Goltz said the snake was about 3.7 metres long and weighed about 24 kilograms.

Also Thursday, Bernard Gallant, co-ordinator at the Magnetic Hill Zoo in Moncton, told the court he had visited Savoie's Reptile Ocean store four or five times over the years, and often conferred with Savoie on reptile issues.

"He showed us he was competent," said Gallant. "I was quite impressed with what he put into the construction of the facility."

He said when the Canadian Wildlife Service was trying to place the snake, it had offered it to the Magnetic Hill Zoo, but they didn't have an appropriate enclosure at the time. Gallant said he told them to approach Savoie.

The Crown expects to call its final witness Friday.