You left out a few details, Neil, including, especially, the Court's indication that the type of [proximate] causation required in this statute might also be satisfied by a non-but-for, independently sufficient condition--as held often in the criminal law as well as in tort law, but also not established by the evidence in this case.
In criminal law, at least in the USA, the doctrine (including the Model Penal Code) is strongly wedded to the but-for test, and so generally uses the extremely deficient "aggregate but-for" test, which cannot distinguish preempted conditions from true causes and literally would allow irrelevant conditions to be treated as causes, to hold unnecessary but independently sufficient causes liable and sometimes even contributing conditions that were neither necessary nor independently sufficient.
Unfortunately, criminal law's aggregate-but-for test made its way for the first (and only) time into the 5th, posthumous edition of Prosser's tort hornbook, put together by others, and was the principal test put forth by the government in Burrage and also the forthcoming Paroline criminal restitution case, as well as by the respondent Amy Unknown in the Paroline case. (All the lawyers involved were well versed in criminal law but had minimal knowledge of tort law.) To limit liability under the statute, the government in Burrage proffered tort law's much more usual "substantial factor" ("material contribution' in the Commonwealth) formulation. The government's briefs in Burrage and Paroline and Amy's brief in Paroline also referred, albeit only very briefly in passing with no elaboration, to the "member of a sufficient set" [NESS] formulation of causal contribution, citing the Restatement Third and yours truly.
The justices in Burrage, especially Scalia, clearly were concerned during oral argument about how to pin down "substantial" and the prospect, if that formulation were used, of mandatory imposition of an additional 20-year prison sentence on someone who made only a small, unnecessary, and not independently sufficient contribution to the death caused by the mixed-drug overdose. Although the heroin supplied by the defendant in Burrage was the major ingredient in the drug mix, the experts could not state that it was either necessary or independently sufficient, but rather only that it contributed (and was the major contributing condition). The same obviously was true for the other drugs in the fatal mix (so---under Neil's but-for theory---none of them caused or contributed to the death, which seems to have occurred miraculously.)
It remains to be seen if the Court will take the same approach in the Paroline case, which involves interpretation of a criminal restitution statute mandating restitution by producers, distributors and viewers of child pornography for "the full amount" of the victim's pecuniary costs (e.g., psychological counseling, lost income, etc.) flowing from her emotional distress caused by such victimization. The focus here is on compensation, not punishment, and the arguments in the briefs and in oral argument focused quite a bit (but, unfortunately, often not too well) on tort law doctrine regarding divisible versus indivisible injuries, factual causation, and apportionment of liability among multiple responsible causes. (The issue that led to the successful appeal, a holding by a court below that "proximate" causation was not required for some listed specific types of pecuniary losses, became a nonissue in the Court, since, even if required, it clearly was satisfied.)
The argument for a contribution basis for liability is much stronger in Paroline, based not only on traditional tort law principles but also on clear Congressional intent that each viewer (who everyone admits could not be a necessary or independently sufficient cause of the victim's emotional state and related damages) be held liable. But it remains to be seen if the Court will truly understand the indivisible nature of the victim's emotional state and related damages and the nature of causal contribution (including the truth that all causes are merely contributing conditions, as part of the filling in of a completely filled in set of minimally sufficient conditions for the consequence), and/or will again be concerned about imposing full (joint and several) liability on each defendant, especially since there is no explicit provision for contribution among the convicted defendants.
The traditional common law of tort, at least in the USA, is not (like criminal law doctrine) fixated on the deficient 'but for' test. The courts and the first and second Restatements have routinely turned to "substantial factor" or "contribution" formulations of the factual cause requirement in overdetermined causation situations. The Restatement Third has finally abandoned the unhelpful and misleading "substantial factor" formulation and provided in the comments to sections 26 and 27 a NESS-based definition of causal contribution (also mentioned and supported in Dobb's hornbook, which has replaced Prosser's as the current leading treatise). (The blackletter of section 27 is a disaster; the reporters in a comment admit it will not handle preemptive causation situations, which they refer back to section 26's but-for test, which however will not handle duplicative or preemptive causation situations.) There are lots of cases properly finding causal contribution even where the condition at issue was not proved to be either necessary or independently sufficient. These cases include the two cases most often cited (incorrectly) in texts as examples of multiple independently sufficient conditions: Anderson v. Minneapolis, St. Paul & Sault Ste. Marie Railway Co. (two fires) and Corey v. Havener (noise from two different motorcycles startled horse).
As you are aware, courts in your own country have acknowledged the deficiency of the but-for test in overdetermined causation situations and that a condition can be a cause even if it is neither necessary nor independently sufficient. See Allianz Australia Ltd v Sim [2012] NSWCA
68 at para [136] per Basten JA (4 April 2012) and
Amaca Pty Ltd v Booth, [2011] HCA 53 53 at [48]
n 62 per French CJ (14 December 2011).
- Richard .