Jesse Samuel would now be entering adulthood.

Instead, a coronial inquest has begun into the death of the 12-year-old, who died from suspected carbon monoxide poisoning while showering at his family’s holiday home.

As the hearing got underway today, his mother, Justine Walker, reflected on the loss of her eldest son.

“It’s been eight long years without our Jesse,” she told the inquest, which is being held in the Queenstown District Court.

“He was like a best friend to me.”

Samuel died in a gas-heated shower at his family’s holiday home in Haast on October 10, 2018.

Previous court proceedings heard that an autopsy found Samuel’s blood was 59% saturated with carbon monoxide after the gas from the water heater had built up in the small, unventilated bathroom unit.

He had been showering in the outdoor bathroom, opposite the kitchen where Walker was cooking dinner.

He chose to shower in the outdoor bathroom because the water pressure was stronger than that in the indoor bathroom.

Walker told the inquest her son was a talented sportsperson and she believed his dedication would have carried him far.

She said he was always helping and coaching his younger brothers, and adored his little sister.

Walker said the inquest would “not give me my life back” but hoped it would mean those involved would be held accountable and that changes would be made.

“We miss him dearly.”

The inquest would investigate the circumstances of Samuel’s death, whether and how the original gas water heater contributed to it, and whether industry training and occupational regulation played a role.

In her opening address, Coroner Mary-Anne Borrowdale said Samuel was a “happy, well, active and cherished” boy when he died.

She acknowledged the length of time between his death and the beginning of the inquest.

“I am conscious Jesse would now be a young man,” she said.

“Jesse is the reason we are here and the motivating force behind this inquiry.”

The coroner said carbon monoxide was colourless, odourless, and tasteless.

“Jesse would not have known he was in any danger.”

Her primary focus was to determine whether a similar tragedy could be prevented from happening to someone else, she said.

In 2021, Central Plumbing Limited, which trades as Laser Plumbing Alexandra, and its director, Michael Cartwright, pleaded guilty to charges laid under the Plumbers, Gasfitters, and Drainlayers Act 2006 in relation to the incident.

They were ordered to pay $70,000 to the family, while Cartwright was fined $19,250 and his company was fined $104,500.

Those court proceedings heard that in 2016, the family had engaged Central Plumbing Limited to install a gas water heater in a transportable bathroom unit, which was then transported and installed at the holiday home.

There was a warning label on the unit, stating it could not be installed in a bathroom, and the need for ventilation was not discussed with the family, the proceedings heard.

The heater was damaged in 2017 after surrounding pipework froze during the winter. In September 2018, a family member replaced the heater with the same model in the same place.

Samuel died a month later.

A WorkSafe investigation found the replacement water heater was not faulty, and the installation of a replacement unit did not materially alter the danger.

Both Cartwright and WorkSafe are expected to provide evidence at the inquest throughout the week.