The High Court has delivered a stinging criticism of the WorkCover Authority over its prosecution of a New South Wales farm owner.

WorkCover took action against Picton farm owner Graeme Kirk after the death of his farm manager in 2001.

The manager Graham Palmer drove an all terrain vehicle down the side of a hill on the property, it overturned and he was killed.

Mr Kirk was fined for breaching occupational health and safety laws but he appealed the matter all the way to the High Court.

Today the court has upheld Mr Kirk's appeal, finding that it was absurd to have prosecuted him over the inexplicable recklessness of the manager, who had skill and experience much greater than his own.

In its judgement the court said it was time for WorkCover to "finish its sport with Mr Kirk."

It ordered WorkCover to pay his costs.