The divisibility of psychiatric injury and taking the stress out of apportionment



Over the past 9 years personal injury practitioners who have litigated occupational stress claims will have had to grapple with an apparent inconsistency in the case law regarding how to approach the divisibility of psychiatric injury.

The leading case in the field, Hatton v Sutherland (2002) ICR 613, included 16 guidelines set out in the judgment of Hale LJ. Numbers 15 and 16 provided as follows:

(15) Where the harm suffered has more than one cause, the employer should only pay for that proportion of the harm suffered which is attributable to his wrongdoing, unless the harm is truly indivisible. It is for the defendant to raise the question of apportionment (paras 36 and 39).

(16) The assessment of damages will take account of any pre-existing disorder or vulnerability and of the chance that the claimant would have succumbed to a stress related disorder in any event (para 42).

Subject to the availability of appropriate and supportive expert medical evidence, this appeared to be an uncontroversial and workable statement of the law.

However, in Dickins v O2 (2008) IRLR5 8, also an occupational stress claim, Smith LJ distanced herself from Hale LJ’s suggested approach:

I respectfully wish ( obiter ) to express my doubts as to the correctness of Hale LJ’s approach to apportionment. My provisional view (given without the benefit of argument) is that, in a case which has had to be decided on the basis that the tort has made a material contribution but it is not scientifically possible to say how much that contribution is (apart from the assessment that it was more than de minimis ) and where the injury to which that has lead is indivisible, it will be inappropriate simply to apportion the damages across the board. It may well be appropriate to bear in mind that the claimant was psychiatrically vulnerable and might have suffered a breakdown at some time in the future even without the tort. There may then be a reduction in some heads of damage for future risks of non-tortious loss. But my provisional view is that there should not be any rule that the judge should apportion the damages across the board merely because one non-tortious cause has been in play.

In a recent decision – BAE Systems v Konzcak (2017) EWCA Civ 1188 – the Court of Appeal has now provided welcome clarification and has confirmed that, to the extent that the two approaches are inconsistent, the guidelines provided by Hale LJ in Hatton are to be preferred and should be followed. The following propositions are derived from the judgments of Underhill LJ and Irwin LJ:

1) It is necessary to distinguish between two types of case:

  • those where there are multiple extrinsic causes of the illness actually suffered, in addition to the alleged breach of duty; and
  • those where all that is said is that the Claimant had a pre-existing vulnerability to psychiatric injury which may have manifested itself at some point in the future.

2) Cases in the first category require the court and the parties to make a sensible attempt to apportion the harm between tortious and non-tortious causes. Whether psychiatric injury is divisible will depend upon the expert medical evidence although Underhill LJ considered that the Court in Hatton believed that apportionment would be possible in “the generality of such cases”.

3) It is important to recognize that the question for the court is whether it is possible to identify, however broadly, a particular part of the harm or suffering which is due to the alleged breach of duty as opposed to other non-tortious factors. The question is not whether the cause of that injury or illness is itself divisible. By way of example, it may be possible to conclude that a pre-existing illness has been materially aggravated by the wrong (in terms of severity and duration of symptoms). This would be an example of the injury itself being divisible. The more problematic case will be those where the claimant suddenly tipped from being simply stressed to being psychologically unwell. This might be a case where the harm is truly indivisible but even in these cases the court should still seek to find a rational basis for distinguishing the parts of the illness which have and have not been caused by the breach of duty, where medical evidence allows it. Indeed, Irwin LJ considered that in order to support the fundamental approach that compensation should never become a windfall, the approach to apportionment may need to be “rough and ready”.

4) Cases in the second category above should be addressed simply by applying a reduction or discount to damages to reflect the fact that the injury may have occurred anyway. They do not require an apportionment. Irwin LJ explained that it was also necessary, in this category of case, for experts to consider “whether a less serious but nevertheless established and defined disorder may not have been achieved before progression to the diagnostic end-state”, that is to say, whether the claimant may have in fact become clinically unwell before he developed the final illness or injury for which he now seeks damages . He also considered that “it should be routine for the experts to assess the level of risk of crossing the borderland between non-pathology and pathology through some other stimulus than the tortious act or omissions” and that whilst this would not be an easy exercise “it will often be possible to give such advice within reasonable parameters of time and to the level of probability”.

This guidance, whilst not without difficulty on the facts of any given case, is very welcome and should assist practitioners acting for both Claimants and Defendants in this difficult area of the law.

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