For some years we have worked with clients in defending claims where it is alleged that their employment has in one way or another negligently triggered the development of Parkinson’s Disease.
The recent case of Smith v McNair  CSOH 154 involved a 54 year old claimant who was involved in a serious road traffic accident which it was claimed resulted in the acceleration of the development of Parkinson’s Disease. This posed the Court of Session the difficult task of determining causation for an illness about which there is considerable scientific uncertainty.
In the first instance the court required to consider whether trauma could be responsible for triggering or worsening Parkinson’s Disease. Thereafter it had to determine whether the claimant had sustained a head injury that resulted in just such a consequence. Whilst medical experts gave evidence in court for both sides, the claimant’s case also relied heavily on epidemiological (i.e. the study of how often diseases occur within separate groups of people and why) evidence. In the absence of anyone involved in the studies cited being present in court to explain their findings, Lord McEwan considered the uncertainty surrounding the issue of causation to have been magnified and was not satisfied that it had been established that the claimant’s Parkinson’s could be linked to her accident.
This case follows the approach adopted by the Scottish Courts in previous similar cases involving such tricky questions of causation against a background of scientific uncertainty. It emphasises the Court’s reluctance to place much reliance on epidemiological evidence where the research data upon which this evidence is based is not placed before it or where the author is not in court to explain the results of his or her studies.