When they got home at 4.30pm, Mr Frizzell noticed Mr Tuhou hadn't returned from his work. He became concerned when he saw Mr Tuhou's lunch bag hanging on a fence and there was no sign of him at 6.30pm. He and his wife started searching.
Mr Frizzell saw the quad bike in an area where he wasn't meant to be working and found Mr Tuhou underneath it. Mrs Frizzell couldn't find a pulse.
Mr Tuhou died from multiple head, spinal and chest injuries after he rode the quad bike down a slope.
It's thought he was focused on a low-hanging tree branch, didn't notice a ledge and the sudden change in the terrain and rode over it, which caused the bike to flip, the court heard.
The bike had been fitted with a weed-spray unit on the front and a fish-bin box fully laden with tools on the rear.
The extra weight of the spray unit meant it was unstable.
Mr Tuhou was not wearing a helmet.
WorkSafe lawyer Natasha Szeto told the court the farm owner, Mr Frizzell, discussed with Mr Tuhou the importance of wearing a helmet but did not enforce it.
Lawyer for the farm company Brad Cuff told the court his clients had farmed all their lives and had never been before the court. He said there had never been an incident of serious harm or a fatality on the farm.
Mr Cuff said the bond between the two families remained strong and they had already made a voluntary payment to Mr Tuhou's family as a form of reparation.
The death had been keenly felt by them and they were deeply sorry, he said.
Mr Cuff said it was Mr Tuhou's preference not to wear a helmet when riding the quad bike.
The lawyer told the court the Frizzells accepted that a helmet may have reduced the severity of the harm caused and they could have forced Mr Tuhou to wear one.
However, they did not want to risk him leaving the farm if they followed through with issuing warnings and subsequent employment action.
He said the Frizzells were both in their seventies and could not run the farm by themselves.
It was not a case where there was a flagrant disregard for safety on the farm and safety had always been a focus for the company, he said.
Judge Bridget Mackintosh said the use of the spray unit may have caused loss of control of the quad bike.
She told the Frizzells the use of the spray unit on the front of the bike pushed "right to the boundary" the accepted industry practices, as it was just at the weight limit of 30kg.
Judge Mackintosh said it was a "serious matter" that the company mounted the spray unit on the quad bike in a way that was against industry advice.
Something as obvious as wearing a helmet was something employers should be vigilant about.
A statement released by Worksafe said Mr Tuhou's death was one of 19 on farms last year.
WorkSafe chief inspector Keith Stewart said an examination of farm-vehicle fatalities found most often the driver had set out to do a "fairly routine task", such as spraying.
"Slopes and tracks with steep drop-offs need to be identified in a risk-management plan and properly communicated - or made 'no go' areas," he said.
