With regard to the tort of negligence, road traffic accidents are exceptional. They are exceptional because they conceal the fact that, often, the factual cause of an event is not discovered. Even where there is no witness to the immediate event of the road traffic accident, it is regularly possible to infer from the circumstances what happened and the knowledge, experience and skill required to do this is not uncommon.
In other fields of human activity this knowledge is not so easily accessed.
Occasionally, even in road traffic accident cases it is seen how important it is to be able to explain the factual cause of an event. In Counihan v Bus Atha Cliath – Dublin Bus  IEHC 51, the Plaintiffs, pedestrians, were injured when a bus crashed into them. The driver had suffered a blackout. He had no basis for anticipating such an event, from his medical history. Thus, on those facts there was no negligence on the part of the Defendant and the Plaintiffs’ claim failed.
[…] problematic. I have adverted to the difficulty of ascertaining, on any particular occasion, exactly what has happened. However, those difficulties are insuperable if what is admissable as âfactâ? or âwhat has […]