Felix qui potuit rerum cognoscere causas
(“Fortunate is he who can understand the causes of things”)
Causation is neither an exclusively philosophical problem nor a matter that only ever troubled the classical Roman poets. As a legal concept, it is pivotal in many areas of law, particularly within the law of negligence. Chiefly, this is explicable by the observation that causation often serves as the last line of defence open to wrongdoers. And yet, despite its apparent centrality in law, many judges still consider causation to be a matter of ‘common sense’. But it is worth remembering Lord Hoffmann’s extra-judicial observations in the Law Quarterly Review (2005) when commenting on Hart and Honoré’s Causation in Law published in 1959. According to Lord Hoffmann,
the great achievement of Hart and Honoré was to unpack the concept of causation when it is used, as the law uses it, to attribute responsibility for things that happen. They showed that when judges say that it is a matter of common sense, they usually mean that it accords with ordinary moral notions of when someone should be regarded as responsible for something which has happened.
The crucial point here is the idea of the ‘attribution of responsibility’. As Lord Hoffmann suggests, law is not so much interested in a neutral inquiry into what caused what; rather it is in the business of attributing responsibility – or in the language of negligence, blame. The recent House of Lords judgement in Gray v Thames Trains illustrates the process at work.
In 1999, when in his early forties, Mr Gray was involved in the Ladbroke Grove train disaster. He sustained minor physical injuries. More significantly, he also suffered post-traumatic stress disorder (‘PTSD’). Having previously been in full time employment with a local council, following the accident his work pattern became increasingly erratic and it appears that shortly before the events that transpired in 2001, he failed to return to work after an agreed leave of absence. In October 2001, he became involved in an altercation with a drunken pedestrian whilst driving his car. Following an argument, Gray drove to his partner’s house, found a knife, went back out to find the pedestrian who he then killed. He gave himself up to the police and was charged with murder. The prosecution accepted a plea of diminished responsibility and the court ordered that he be detained under the Mental Health Act 1983 pursuant to hospital and restriction orders rather than being sent to prison. Gray remains detained in hospital.
In 2005 Gray sued the train operator who admitted liability for the train disaster. Gray raised a number of claims against the defendants: loss of earnings (on a full basis or in the alternative, on a partial basis); general damages for his feelings of guilt, remorse and so forth; and an ‘indemnity’ in the event that his victim’s family were to sue him in respect of the unlawful killing at some point in the future. Put at its simplest, and in terms of a ‘chain of causation’, Gray’s argument was that the defendants’ negligence caused him to suffer PTSD which in turn caused him to commit manslaughter which in turn led to his conviction and subsequent detention under the Mental Health Act which caused him to suffer the various heads of loss (actual and prospective) claimed. Although the defendants accepted liability for the accident, they denied liability for any losses that occurred after the manslaughter. They relied on the maxim ex turpi causa non oritur actio – the public policy defence which prevents someone from obtaining compensation for the consequences of his own criminal act.
In order to fully grasp the House of Lords’ judgement, it is important (as in all negligence cases) to keep the various heads of loss separate because different considerations might apply to the different heads of loss. For example, Gray’s inability to work after the manslaughter conviction can on one view be related to his detention in hospital whereas his claim for an indemnity is unaffected by his detention (he could face a claim from the deceased’s dependants whether or not he was detained in hospital). General damages for ‘loss of liberty’ could at least partly be related to the detention, whereas his feelings of guilt and remorse over the manslaughter are clearly unrelated to his detention. For the sake of exposition here, only the loss of earnings claim will be considered.
Loss of Earnings
The claim for loss of earnings was put in a number of ways. Up to the House of Lords, Gray put his argument in two ways: first, his loss of earning capacity (whether on a full or partial basis) had been sustained before the manslaughter and was therefore a ‘continuing loss’ even after his detention. When it is recalled that Gray had effectively stopped working before he killed the pedestrian, the logic of this argument becomes clearer. This was the argument accepted by the Court of Appeal. The alternative argument (which assumes that the loss of earnings was in fact occasioned by his detention rather than having ‘crystallised’ earlier) was that there was an unbroken chain of events between the initial accident and his loss of earnings that ran thus: accident → PTSD → killing of pedestrian → manslaughter conviction → sentence of detention → inability to work → loss of earnings (damage). The Court of Appeal did not accept this argument. It should also be noted that under both analyses, Gray accepted that it was the manslaughter conviction that led to his detention in hospital. This may seem obvious, but the reason for noting this admission is that in the House of Lords, Gray argued for the first time that detention in hospital may have occurred irrespective of any criminal act on his part. The reasoning for adopting the new position appears to have been two-fold: first, by resiling from an acceptance that his detention was occasioned by the conviction it might allow an argument to the effect that his detention in hospital was imposed with a view to his treatment rather than punishment for his crime; secondly, by detaching the conviction from the sentence in this way not only does the criminality of Gray’s act diminish in significance, but it allows him to argue that he might have been detained irrespective of any criminality on his part. In this way, Gray was hoping to persuade the House of Lords that his detention should effectively be ignored. The strategic reason for refining the argument thus was to nullify the significance of his conviction (criminal act) and detention (legal consequence) to the defendants’ legal arguments based on ex turpi causa (loosely: no compensation for consequences of criminality).
The House of Lords did not accept the newly formulated argument. Although Lord Phillips MR appeared to accept the proposition that it might be possible to claim compensation in circumstances where a criminal sentence in the form of a hospital order was imposed primarily with a view to treating rather than punishing an individual, in this case the sentencing judge “must have” considered the seriousness of Gray’s offence as being significant when reaching her judgement about the appropriate sentence to impose on Gray. It should be noted that Lord Phillips here makes an assumption about what motivated Rafferty J to impose a hospital and restriction order on Gray. Lord Phillips was a little more nuanced on this issue than Lord Hoffmann who had said
In my view it must be assumed that the sentence (in this case, the restriction order) was what the criminal court regarded as appropriate to reflect the personal responsibility of the accused for the crime he has committed (emphasis added).
Again, Lord Hoffmann also proceeds on the basis of an assumption about what motivated Rafferty J to impose the hospital order, but rather than allowing for the possibility that ex turpi might not apply in some limited circumstances of criminal behaviour, Lord Hoffmann sweeps up all distinctions into an overarching concept of ‘personal responsibility’ as underlying all criminal sentences. In fact, he goes even further by hinting that ex turpi might even apply in circumstances where an individual was insane at the time of committing his offence. The practical effect of both Law Lords’ assumptions, however, is to maintain a link between Gray’s conviction and his sentence. Lord Phillips and Lord Rodger also dismissed Gray’s argument that he might have been detained irrespective of the manslaughter by reference to the psychiatric evidence adduced at trial. That evidence, compiled by a psychiatrist who examined Gray before the killing, stated that it could not be said on the balance of probability that Gray would have been detained in hospital had he not committed manslaughter. The net result of these opinions, therefore, was that the connection between Gray’s conviction and his sentence was maintained. Gray was therefore left with his original alternative arguments namely either that his loss had ‘crystallised’ before the manslaughter (the ‘crystallisation’ argument) or that there was an unbroken chain of events between the accident and his loss of earnings (the ‘unbroken chain’ argument).
Although Lord Phillips gave the first judgement, it is convenient to start with Lord Hoffmann’s opinion as Lord Phillips agreed with most of it and Lord Scott with all of it. The vast majority of Lord Hoffmann’s opinion concentrates on the unbroken chain argument and he poses the central question as:
whether the intervention of Mr Gray’s criminal act in the causal relationship between the defendants’ breaches of duty and the damage of which he complains prevents him from recovering that part of his loss caused by the criminal act … On the one hand, but for the accident and the stress disorder which it caused, Mr Gray would not have killed and would therefore not have suffered the consequences for which he seeks compensation. On the other hand, the killing was a voluntary and deliberate act. The stress disorder diminished Mr Gray’s responsibility but did not extinguish it.
Posed in this way, it can be seen that Lord Hoffmann ‘locates’ the damage at the end of the causal chain which would otherwise be unbroken on the basis of the ‘but for’ test. It also assumes a causal link between the criminal act and Gray’s subsequent inability to earn. The language is that of causation but as noted in the opening remarks of this article, causation in law is inextricably bound up with questions of responsibility, and in his final sentence Lord Hoffmann hints at the solution he will eventually adopt.
Plainly, in terms of pure chronology, Gray’s criminal act ‘intervened’ as it occurred between the defendants’ original negligence and Gray’s continuing loss; but it is trite law that the intervention has to be legally significant to ‘break the causal chain’. He reminded himself that a deliberate act by the claimant is not by itself necessarily sufficient to relieve the defendants of liability if the claimant’s act could be explained by a state of mind caused by the defendants’ wrong: Corr v IBC Vehicles Ltd. On traditional causation analysis, therefore, Gray’s deliberate act might not break the chain of causation. It is at this point in the analysis that the Defendants’ arguments based on ex turpi enter the equation.
According to Lord Hoffmann, the ex turpi doctrine can be interpreted widely or narrowly. The wide interpretation of the rule provides that a person cannot rely on his own criminal act (broadly speaking) to mount a claim for compensation in civil law; the narrow interpretation precludes recovery of compensation if the loss is consequent on a criminal sentence or ‘punishment’. According to Lord Hoffmann, the underlying rationale for the ex turpi rule is grounded in ‘policy’: the wide interpretation is grounded in the policy concern that “it is offensive to public notions of the fair distribution of resources that a claimant should be compensated (usually out of public funds) for the consequences of his own criminal conduct.” The narrower interpretation is grounded in the somewhat different policy concern that to award a criminal compensation might risk bringing the justice system as a whole into ‘disrepute’ because it would be “inconsistent” to allow a person to claim compensation in civil law in respect of consequences for which criminal law has deemed that person responsible. Lord Hoffmann appears to have based his conclusions very firmly on Samuels JA’s approach in State Rail Authority of New South Wales v Wiegold  who said that
If the plaintiff has been convicted and sentenced for a crime, it means that the criminal law has taken him to be responsible for his actions and has imposed an appropriate penalty. He or she should therefore bear the consequences of the punishment, both direct and indirect. If the law of negligence were to say, in effect, that the offender was not responsible for his actions and should be compensated by the tortfeasor, it would set the determination of the criminal court at nought. It would generate the sort of clash between civil and criminal law that is apt to bring the law into disrepute.
Lord Hoffmann’s opinion was echoed by Lord Rodger who cited Rothstein J in British Columbia v Zastowny in similar vein: to allow a claim arising from a criminal act is to introduce “an inconsistency in the fabric of the law that compromises the integrity of the justice system.”
Applying the narrow interpretation of the ex turpi rule to Gray’s case, Lord Hoffmann held that Gray’s loss of earnings was consequent on his detention which was lawfully imposed on him by a criminal court; and because it had to be assumed that Gray’s sentence was a reflection of the criminal court’s view of his personal responsibility for the manslaughter, it would be inconsistent for a civil court to shift that responsibility onto someone else (in this case, Thames Trains).
There are a number of problems with Lord Hoffmann’s analysis. As noted earlier, Lord Phillips adverts to the first: Lord Hoffmann seems to proceed on the basis of an assumption – that the sentence was in fact a reflection of the criminal court’s view of Gray’s personal responsibility for the sentence. As Lord Phillips suggests, it is plausible to take personal responsibility out of the equation when a convict is sentenced to hospital detention. It is possible that the sentence is motivated by a need to treat the convict rather than to punish commensurate with personal responsibility. That said, Lord Phillips also assumes that in this case, the criminal judge, Rafferty J, must have sentenced taking into account the nature of the offence rather than being predominantly concerned with treating Gray’s mental disorder. That assumption appears to be based on the seriousness of the offence (manslaughter). It would follow from this that in any case involving a serious criminal offence it is likely that the narrow interpretation of ex turpi would apply and that the offender would therefore be precluded from claiming compensation in civil proceedings.
However, there is a more fundamental objection: surely the logical and consistent conclusion to draw from Lord Hoffmann’s observation that ‘diminished responsibility’ does not “extinguish” responsibility is that a criminal court is thereby signifying that Gray was partially and not wholly responsible for the killing. It follows that it would not be inconsistent for a civil court to hold the defendants partially responsible for damage consequent on a criminal conviction by holding that Gray had contributed to his damage (as occurred in Corr). To hold otherwise, as the House of Lords did, is to relieve the defendants of all responsibility for all consequences post-dating the killing. In other words, the defendants receive a windfall because of the claimant’s criminal act to which the Defendants have in fact contributed by their negligence. It follows that it can be argued that far from promoting consistency, the decision in Gray actually tends towards inconsistency and thereby (if the policy concern is valid) brings the law into disrepute. Lord Brown was the only Law Lord who seems to have been live to this problem, but he too reached the same conclusion as his brethren and appears implicitly to have justified this outcome by considering criminal responsibility to be somehow more blameworthy than tortious responsibility.
Quite apart from the apparent inconsistency in result, the Law Lords’ common opinion appears to be founded on an assumption that responsibility has the same quality in the very different spheres of criminal and tort law. It is not immediately obvious that that is the case. Even so, a further problem – particularly with Lord Hoffmann’s analysis – is that it proceeds on the assumption that the damage for which compensation is sought was caused by the criminal law ie that it was the detention that caused the loss of earning capacity. As noted above, Gray advanced the alternative argument that his loss of earning capacity had crystallized prior to the manslaughter. In response to this argument, Lord Hoffmann was uncharacteristically brusque. He held that this argument was precluded by Jobling v Associated Dairies although he did not explain why Jobling precluded Gray’s alternative argument.
Jobling, it will be recalled, involved a case where the claimant was prevented from claiming continuing losses where a natural illness had ‘overtaken’ the damage caused by the Defendant. In Gray’s case, the ‘supervening event’ was not a natural event. Jobling is also conventionally distinguished from Baker v Willoughby where a claimant who had suffered damage to his leg in a road traffic accident was later shot in the same leg which had to be amputated. In Baker, the claimant was permitted to claim a continuing loss in respect of the damaged leg even though he no longer had it. Many have found it difficult to reconcile the two cases, but both remain good law. A tentative distinction offered at times is that Baker involved two torts whereas in Jobling, the supervening event was nobody’s fault: it was just a part of the ‘viscissitudes of life’. In Gray, Lord Brown takes the “viscissitudes principle” from Jobling and appears to extend it to cover the sort of claim raised in Gray. In Lord Brown’s opinion, Baker represents a “departure” in the “interests of justice” from the default position (the viscissitudes principle) and the question is therefore ‘what sort of intervening events can a defendant rely on to relieve them of liability?’ The answer, according to Lord Brown, is to look at the viscissitudes principle in conjunction with the ‘consistency’ principle referred to by Lords Hoffmann and Rodger and to say that as a claim for loss of earning capacity is always a contingent claim (all sorts of things could affect it), where a contingency (such as imprisonment or hospital detention) has in fact taken place, it has to be taken into account rather than ignored. In other words, a defendant is entitled to rely on an intervening event if that intervening event is the claimant’s own criminal act, to put an end to the claim. Lord Brown did recognize that this was to give the defendants a ‘windfall’, but he felt that if a claimant such as Jobling could not claim an ongoing loss where the intervening event was no fault of his, then justice required the viscissitudes principle to operate to terminate a claimant’s claim where the intervening event was very much the claimant’s own fault.
Although Lord Brown attempted to explain why Gray was more like Jobling than Baker, his analysis also overlooks the possibility of shared responsibility. If all of their Lordships’ judgements are ultimately grounded in the idea of personal responsibility, the effect of those judgements is to extinguish the defendants’ personal responsibility altogether and it is surely questionable whether that result accords with “ordinary moral notions” of responsibility. The only real distinction between Corr and Gray appears to be that suicide is no longer a criminal offence. To be fair, it is likely that no arguments were raised on the basis of contributory negligence, but the message remains clear: crime does not pay.
 Virgil, Georgics, no 2, l 490 quoted in Wilson, J. Inverting the Pyramid (Orion: London) 2008
 Lord Hoffmann, Causation, Law Quarterly Review (2005) 593
  UKHL 33
 ibid para 24.
 A full loss would be calculated on the basis that Gray would never work again; a partial loss is calculated on the basis that Gray could have undertaken some work but would effectively be working on some part-time basis for the rest of his life. Traditionally, a loss of earning capacity claim would be formulated as a ‘handicap on the open labour market or Smith v Manchester claim, but it does not appear that that is how Gray put his claim in this case.
 He gave the example of a ‘minor offence’ committed by a mentally disturbed individual leading to a hospital order.
 Paragraph 41 of the judgement.
 Paragraph 42.
 Lord Scott also agreed with Lord Rodger, but his judgment is slightly different from that of Lord Hoffmann.
 Paragraph 27.
 That is to say it was the criminal act that is the most immediate cause of his loss of earnings rather than the original PTSD.
  AC 884
 Paragraph 29.
 Paragraph 51.
 (1991) 25 NSWLR 500
  1 SCR 27
 Paragraph 102 of the judgment.
  AC 794
  AC 467
 paragraph 96 Gray.