Date: Fri, 16 Sep 2005 10:36:38 +0100

From: Charles Mitchell

Subject: Apportionment and causative potency

Your response raises several interesting points, Allan, and has made me think that my example is a bad one, though I'm not ready to give up on the idea of relative causative potency just yet.

If D1 driving at 60 mph hits a pedestrian then he is likely to cause him significantly more damage than D2 who hits a pedestrian when driving at 20 mph. Hence if they both hit him at the same time and cumulatively cause him harm then it is likely that a greater proportion of this harm was caused by D1's actions than by D2's actions.

If we knew for sure that (say) three-quarters of the harm was caused by D1 and one-quarter by D2, then really we'd be saying that they have caused him two different harms, and that D1 was the sole cause of one and D2 the sole cause of the other. This would then make D1 solely liable for one and D2 solely liable for the other, and so they wouldn't be liable for the same damage and there would be no contribution claim. The courts quite like doing this, even in pretty unpromising circumstances (e.g. Rahman v Arearose Ltd [2001] QB 351), because it means they can avoid making D1 and D2 pay for harm which they haven't caused.

But let's say the harm suffered by the victim is indivisible. If we know for sure that either D1 or D2 would have caused the whole of the harm, absent the other, then the point I overlooked when I wrote my example was of course that neither is liable on a but-for test because each can say that the other's actions caused the harm. We've arrived at Fitzgerald v Lane [1989] AC 328: the court must fudge it and say that their actions, considered separately, were each a cause of the harm, and that this is enough for liability.

How should an apportionment be made between D1 and D2 in this kind of case? You would say that neither defendant's actions can have been a more potent cause of the harm, producing the conclusion that an apportionment based solely on causative potency would have to be equal. On reflection I would arrive at the same conclusion, but for a slightly different reason, namely that we have no rational basis for division of causation between them and so we must fall back on the rule that where a court has no reason to make an unequal apportionment it must apportion equally: cf EM Baldwin & Son Pty Ltd v Plane [1999] ATR T91-499.

'Ha!' David is happily exclaiming. 'No rational basis for division of causation, eh? My point, I think.'

But wait ... As I said at the start, it's not a good example. It runs us into evidential problems and we have to use a default rule. But let's take another example, in equity this time. Suppose that D1 is a bad trustee and D2 is a dishonest assistant who helps him launder misappropriated trust funds. Suppose that we can prove that D1 would have taken the trust funds whether or not D2 had helped him, but that D2's help has made it a bit easier for D1 to carry through his dishonest scheme. On a but-for basis D2 has not caused the beneficiaries' loss, but he's still liable to them because he helped D1: Grupo Torras v Al-Sabah (No 5) QBD 24 June 1999; Casio Computer Ltd v Sayo [2001] EWCA Civ 661.

If David is right that causative potency is a meaningless concept, then we can only say that D1 and D2 are equally the causes of the beneficiaries' loss and that D1's actions have had no greater impact on the beneficiaries' position than D2's actions. But can we not meaningfully say that D1's actions in initiating a scheme to steal from the beneficiaries and salt the money away are a more potent cause of their loss than D2's actions in moving money from one bank account to another. on D1's directions? Cf Schott Kem Ltd v Bentley [1991] 1 QB 61 at 76; Arab Monetary Fund v Hashim The Times 11 Oct 1994. Take D2 out of the picture and the loss would still be incurred; take D1 away and it wouldn't be. David would say that this makes no difference but I doubt this.

Best wishes
Charles

At 14:02 15/09/2005 +0200, you wrote:

I find this discussion really interesting, but I’m not sure that I can make any sense of causative potency in this context. Let’s take the example:

Suppose I'm on a pedestrian crossing and two negligently driven cars hit me simultaneously, one [D1] travelling at 60 mph and one [D2] travelling at 20 mph. I am badly injured. Both drivers have caused my injuries on a but-for test. But I would still argue (from my hospital bed - I just keep on going) that the actions of D1 driving the first car were a more potent cause of my injuries than the actions of D2 driving the second car.

I don’t think that this is the best example because it is natural to assume that the car going faster would have caused more damage (and hence should be liable for more regardless of the contribution rules). Do we still have the intuition that D1 was more casually potent than D2 if we can show that P would have been injured to exactly the same extent if only D2 had been present? I don’t, at any rate. If P would have suffered the exact same injury whether D1 or D2 had been absent, how can we say that one was more causally potent than the other? Has this got something to do with overdetermination? Is it possible to provide a definition of causal potency?

(Sorry if this has already been given and I have missed the post, but I am very interested in these ideas.)

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