A business owner says his “terrible error of judgment” while using a slasher to clear a paddock led to a projectile piece of wire lodging in the brain of an Adelaide great-grandfather, ending his life.

In October 2023, Ioanniss “John” Gatzopoulos, 79, was pulling weeds at a Salisbury Plain property, when a projectile from a slasher entered his head.

Five hours later, he died in hospital.

On Thursday, the slasher operator – Jackson’s Slashing owner Guy Warren Jackson – was convicted by the South Australian Employment Tribunal of failing to ensure the safety of two people was not put at risk by work he carried out as part of his business.

The 60-year-old was also fined $30,000 and ordered to pay $19,967 for Mr Gatzopoulos’s funeral expenses, after the court found he failed to take any steps not to operate the slasher near people, despite an “obvious” need to do so.

In a victim impact statement read to the court, Mr Gatzopoulos’s eldest child Kathy Nikou described her family’s lasting grief and her daily memory of tears running down her father’s face during the bishop’s prayers in his last moments.

Mr Gatzopoulos was described as the family’s “rock and mentor” and a deeply loved great-grandfather who was devoted to community involvement and the Greek Orthodox Church.

In his judgment on Thursday, Stephen Lieschke, a deputy president of the court, said Mr Jackson had been let into the Salisbury Plain property by Mr Gatzopoulos, who lived nearby, along with another neighbour, Dimitrios Tassapoulos.

Mr Jackson entered on a Kubota L5740 tractor, connected to a Howard Nugget 180 S4 Slasher.

He started slashing while the two neighbours removed weeds around the gate, before coming to a distance of about 5m between the slasher and Mr Gatzopoulos.

Mr Jackson then “heard a ‘tinkle’ sound through the slasher” and turned over his left shoulder to see Mr Gatzopoulos having collapsed to the ground, bleeding from his head.

The slasher operator performed first aid while waiting for an ambulance, and Mr Gatzopoulos was taken to hospital about 8.20am, where it became apparent a metal object had lodged in his brain, causing a catastrophic injury.

He passed away at 1.15pm.

In court, Mr Jackson read out a written apology to the family, acknowledging he had made “a terrible error of judgement, which had cost Mr Gatzopoulos his life”.

“The defendant stated he accepts full responsibility for his actions and their devastating consequences. He offered his deepest and most heartfelt apology for the loss and suffering he had caused,” Deputy President Lieschke said.

Mr Jackson faced a maximum fine of $300,000, which was reduced to $30,000 in recognition of his early guilty plea, his contrition, the small size of his business and his financial means.