Wright v AIB & Ors: When you eliminate the impossible, whatever remains, however improbable, must be the truth

john_deere_7950iJohn Deere, as third party defendant, appealed the decision of the High Court to award damages against it, on the grounds that the court’s findings of causation could not be legally sustained. The Supreme Court rejected the appeal holding that the trial judge could apportion blame where there was two equally improbable but possible causes of the accident, one of which must be the cause, and either of which could make the defendant liable.



Thomas and William Wright are agricultural contractors. AIB purchased a John Deere harvester from Geary’s Garage Ltd and leased it to Wrights. The Wrights employed Denis Scollard to operate the harvester, which harvested freshly cut grass by picking it from the ground and blowing it through a chute into a trailer. It was not uncommon, though, for the harvester to become blocked by damp grass clogging the entry to the chute. Blockages could be cleared by opening a hatch on the blower box and freeing the blockage. The blower box, however, contained moving parts and was not to be opened without first disengaging the power to it. Other models of the harvester had the hatch on the chute away from the moving parts.



Scollard gave evidence at the trial that, on the day of the accident, he was operating the harvester when it became blocked. He disengaged the power to the blower, removed the hatch and began to free the blockage. The internal parts began to move and injured Scollard’s hand. Other witnesses who were present supported this evidence. John Deere, however, introduced expert evidence which suggested that the internal parts could not move unless the power was engaged. Against that though, Wrights introduced expert medical evidence which suggested that Scollard’s injuries could only have been caused by the internal parts of the blower moving at a slower speed than if the power was engaged: had the power been engaged the injuries to Scollard’s hand would have been more severe. Therefore, the power could not have been engaged when the accident happened.


High Court decision

Irving J in the High Court determined that the accident happened when the power was disengaged. And, as the hatch was positioned on the blower box rather than on the chute, the harvester was “not fit for purpose within the Sale of Goods and Supply of Services Act 1980”. John Deere appealed that decision on three grounds: the decision on causation could not be sustained legally, the injuries were not foreseeable and the judge was incorrect to find that the Wrights were not guilty of contributory negligence, as they had failed to give adequate instruction to their employee as how to carry out his duties.


Supreme Court

Clarke J, with McKechnie and MacMenamin JJ concurring, held that the trial judge was justified in her determination of causation. Although the cause attributed to the accident––that the internal parts moved while the power was disengaged––appeared to be improbable, there was expert evidence that the only alternative cause was equally improbable. Therefore her finding was sustainable upon the evidence available. As the accident was held to have happened while the power was disengaged, the claim of contributory negligence must be rejected. And, as the hatch was unnecessarily located close to the moving parts, and was placed in a different position on other models, the risk of injury was foreseeable. The Court rejected the appeal and affirmed the finding of the High Court.

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