2 Regulatory standard setting and public education

First, tort adjudication performs a social function by educating the public, policymakers, private actors, and practitioners about the appropriate way of dealing with a risk. Above, all courts operate as regulatory standard setters. Although court rulings primarily have binding force between the parties to the proceedings, courts set precedents that, depending on the content and scope of a decision, also determine the legally required conduct of non-litigants belonging to the same social group as the defendant.Footnote ¹⁴ Moreover, through rulings courts amplify norms of social and legal importance thereby given the actors who are involved in risk regulation on several levels (global, supra-national, national and local) guidance about the desired risk regulatory standards.Footnote ¹⁵ Tort adjudication enhances problem signalling, and leads to the legal (de)legitimising of the way actors in society deal with risks. As Linden put it, civil courts can perform a sort of ombudsman function by addressing issues that socially do not receive the attention indicated.Footnote ¹⁶

Both courts and regulators respond to each other’s alleged failures in addressing issues of social importance. In that respect it should be stressed that some authors see in the failure of courts to deal with the hazard of the industrial revolution, an explanation for the rise of the regulatory state.Footnote ¹⁷ Others, however, argue that courts play an important gap-filling role.Footnote ¹⁸ The successes and failures of both litigation and regulation determine each regulatory role. In this contribution the focus is on the role of the court.

The way a Western court dealt with asbestos litigation is exemplary for this role of the courts. Asbestos litigation has been a major driver in developments in the tort law. It led to the acceptance of new or the stretching of existing legal concepts, such as the duty of care, limitation periods and causation requirements.Footnote ¹⁹ For instance, from the 1990s the Dutch Supreme Court accepted high standards of care on several occasions, especially in those circumstances where specific public regulations were lacking or were inadequate. And while it primarily offered recourse for victims of the risk behaviour of the defendant,Footnote ²⁰ the court also filled (perceived) regulatory gaps or imperfections in risk regulation by repeatedly ruling that private actors, such as producers and employers, are under the (proactive) duty to take measures to prevent asbestos-related diseases. The court even repeatedly ruled that the fact that the use of asbestos was socially accepted, or even stimulated by the government, does not dismiss the responsibility of operators dealing with asbestos. This case law has set a precedent in the Netherlands, also across the case law of other risks in the jurisprudence of the Supreme Court, such as the risk associated with the use of lead paint.Footnote ²¹

The preceding does not, of course, mean that courts are always willing to operate as gap-fillers. Strengthened by the flexibility of tort law and some courts’ willingness to allow claims for health and environmental risks, plaintiffs might invite courts to stretch the boundaries of tort law even more to fully embrace tort law’s regulatory potential. In some instances, these claims balance on the boundaries of tort law. A striking example in this respect can be found in US litigation relating to climate change, gas additives, destruction of fishing stock and litigation against manufacturers of inter alia asbestos, tobacco, lead paint and guns on the basis of the tort of public nuisance.Footnote ²² According to the American Restatement (second) of Torts, “a public nuisance is an unreasonable interference with a right common to the general public.”Footnote ²³ Although product liability would be the logical basis for a claim against manufacturers of many of the above-mentioned risks,Footnote ²⁴ the plaintiffs, who were private individuals but also States, attempt(ed) to move the tort of public nuisance beyond its traditional meaning to make it a “catch all tort” for industrial risks that are posed to the public at large. Under this tort it would be easier to prove liability for risks imposed on society as such, than it is on the basis of other liability standards, such as negligence or product liability. Consequently, the tort of public nuisance would provide a major vehicle for successfully attacking lethal (but also legal) products through tort law. For most of the courts,Footnote ²⁵ such a broad tort of public nuisance has been a bridge too far and thereby they are acknowledging the limits of their role as risk regulatory standard setters. By denying these claims they explicitly considered that, inter alia, the products as such are legal, accepting a broad tort leads to floodgate concerns and its application requires the balancing of several interests which does not belong to the courts’ domain but to the legislators’.Footnote ²⁶ It is beyond the topic of this contribution to assess the validity of the results of this litigation.Footnote ²⁷ The point to be made is that these rulings also amplify norms and give guidance about the role tort law can or cannot play in the context of risk regulation. In a sense, one could even argue that it legitimises the use of the products or technologies that were subjected to litigation.

The above-painted picture is in practice complex. It is not easy to quantify and specify tort’s regulatory effects. First, except for anecdotal material and case studies there is not much structural empirical knowledge of the actual social impact of court rulings and the causal mechanisms that influence to what extent specific rulings perform an educational function.Footnote ²⁸ Secondly, each case is factually unique and, particularly in negligence-based claims, the facts to a great extent determine the outcome of a case. For instance, in many systems to establish liability under negligence, courts use a list of non-exhaustive viewpoints in examining whether the defendant owed a duty of care towards the plaintiff, such as the severity of the risk and the burden of precaution. These viewpoints and their application vary according to inter alia the characteristics of the risk involved, the nature of the parties involved and their underlying legal relationship. The reasoning of courts based on these viewpoints is often tailored to the specific facts at hand, thereby leaving the broader meaning and scope of such a ruling potentially somewhat in the clouds, although established case law gives some general rules (eg “more precaution is required when the risk is more severe”).

3 Behavioral and policy effects

Next, tort adjudication could affirm or alter the behaviour and/or risk management policies of private actors or public authorities. In this respect, one could make a distinction between actor specific behavioural effects, actor general behavioural effects, risk specific behavioural effects and risk general behavioural effects, although the distinctive line between the several concepts is thin.Footnote ²⁹ Depending on the combination of the occurrence of these effects, the regulatory impact of tort adjudication can be wider or narrower. Again, however, the lack of comprehensive empirical evidence should be borne in mind.

Tort adjudication has specific behavioural effects when a parties’ practice is affirmed by a court’s decision, when a party is legally forced to change its behaviour or when the actor wants to avoid being exposed to further legal proceedings, eg for reasons of public exposure and publicity, costs of litigation and costs of awarded damages.

General behaviour effects relate to tort law’s effect on the behaviour and/or policies of non-litigants, such as an industrial sector or the government, and can occur through several mechanisms.Footnote ³⁰ One could think of the adoption of industry policy guidelines and the introduction and enforcement of regulation of industry by the government because of a court’s ruling. Especially the effects of litigation on governmental risk regulation are interesting to note. In several jurisdictions, examples of governmental regulation induced by litigation are, according to some scholars, to be found in the context of asbestos,Footnote ³¹ tobacco,Footnote ³² air pollution,Footnote ³³ weight-loss pills,Footnote ³⁴ HalcionFootnote ³⁵ and PFOA-chemicals.Footnote ³⁶ Courts can, for instance, play an important role in overcoming information deficits and uncertainties about risks that paralyse(d) governmental action. Although courts themselves also face information deficits,Footnote ³⁷ information on risks that are generated through legal proceedings and that would not have been available to the regulator otherwise, can lead to public and political condemnation of industrial practices and create an impetus for regulatory action. A well-known example in this respect is the regulatory effects of some of the tobacco litigation in the US. During this litigation, ultimately the misleading and fraudulent tactics of the industry to withhold information about the risks of smoking or even to actively disseminate information that falsely denied the existence of these risks became apparent. According to some scholars, this litigation influenced the political and public attitude towards smoking and the tobacco industry and led to public condemnation of the industries’ practices. It resulted in more stringent regulation by US Congress.Footnote ³⁸

Last, judicial decisions can influence the behaviour and policies towards the risk that was central to the legal dispute but can also change behaviour related to other similar risks. Thus, under certain conditions, nanotechnology “producers” might draw lessons from asbestos case law. Important to note in this respect is that, if the activity that creates a risk is no longer carried out or the product is not on the market anymore, the behavioural incentives of a court’s ruling are only present if there are risk general effects, ie when it is clear that the ruling applies to other risks.

4 Extra-judicial effects

The third regulatory feature is that, considering the previously discussed features, judicial decisions also affect the non-legal interests of third parties. In other words, court rulings have extra-judicial effects. For instance, the Urgenda judgment has implications for the Dutch energy supplies, as it requires a change of Dutch energy policies. Apart from such policy effects, one could think of influences on the availability and costs of insurance,Footnote ³⁹ the availability of public funding for achieving policy objectives in case of public authority liability,Footnote ⁴⁰ floodgate effects and the willingness of actors to bring new products to the market and implications of court rulings for product prices. Although some authors claim the occurrence of extra-judicial effects – some, for instance, argue that tort law’s regulatory effects lead to risk aversion on the side of developers of innovative technologies with adverse impacts on innovation – Footnote ⁴¹ it is important to stress again that the empirical evidence about the occurrence of these effects as a consequence of specific court rulings is scarce. Nonetheless, as will be highlighted out below, courts do take such concerns into account.Footnote ⁴²

1 False positives and false negatives

While judicial risk regulation occurs, and is recognised in both civil law and common law jurisdictions, the question remains whether, and if so how, civil courts could consider the regulatory effects of a given or an intended ruling. To answer that question, first the essence of deciding upon tort claims in the context of uncertain risks has to be addressed.

Central to judicial decision-making in the context of uncertain risks are the concepts of a false positive and a false negative. Both concepts relate to a wrong estimation of the existence, characteristic(s) and manageability of a risk.Footnote ⁴³ In case of a false positive, one overestimates a risk and acts accordingly, but as it later turns out, due to a progressively more detailed understanding of the risk, the risk turned out not to be present or less severe than initially thought. When a false negative occurs, the risk is underestimated, while it later turns out that the risk does exist or is more severe than initially thought.

Tort proceedings are framed in the terminology of false negatives. In injunctive relief cases dealing with allegedly failing risk policies or management, the plaintiffs try to correct an alleged excessive focus by the defendant on the avoidance of a false positive and aim to direct the focus on the avoidance of a false negative. In claims for damages, victims seek compensation for a materialisation of a risk because of the defendant’s alleged improper risk management, in other words, that he wrongfully let a false negative occur.

It is the court’s task to assess the legal merits of the case and determine whether a false negative is likely to occur or occurred and the defendant is to be held accountable for it. The outcome of this assessment, of course, depends on the applicable legal rules on, among other things, the burden of proof, standards of proof, other rules of evidence, causation, and the relevant grounds for liability. Though, if the scope and application of these rules are unclear or the plaintiffs aim to stretch their boundaries, courts also have to decide upon the modification of legal concepts to decide the case.Footnote ⁴⁴ Especially in that situation, courts might bear in mind the potential errors both for the litigating parties and, as a consequence of the regulatory implications of tort law, non-litigants. These involved errors can be summarised as follows:

1. – over-compensation;

2. – under-compensation;

3. – litigation costs;

4. – costs of implementing rulings into corporate and/or governmental risk policies;

5. – victims who are deprived of civil recourse;

6. – exposure to legal proceedings;

7. – the occurrence of undesirable extra-judicial effects (section II.2);

8. – over-regulation, eg due to case law that amplifies too stringent norms and/or generates incentives that lead to excessive care;

9. – under-regulation, eg amplification of too low standards which might generate incentives for ostrich like behaviour in situations of risks and uncertainty;

10. – over-litigation/flood gate concerns;

11. – under-litigation, ie plaintiffs are discouraged by initiating legal proceedings because of inter alia low chances of success and legal costs;

12. – costs for the legal system, eg as a consequence of an increase of (ill-founded) claims.

2 Empirical and normative difficulties in evaluating tort’s impact

Resolving the issue of false positives and false negatives involves both a normative and empirical issue.

Answering the normative question needs an analysis as to which of the potential errors one prefers (or better: seems to be the least problematic) on normative grounds. For instance, does one prefer the chance of over-deterrence or under-deterrence? And when do we find an increase in claims problematic, and for what reasons? The normative framework for answering such questions is, to my best knowledge, under-developed and requires an analysis of several legitimacy theories of judicial law making within tort law and their application to particular legal issues.Footnote ⁴⁵

The empirical question relates to either the ex-post evaluation of judicial decisions or to the ex-ante prediction of their potential regulation effects. With respect to the former, the empirical qualification of the results of litigation as either a false negative or false positive is often contentious. Scholars, for instance, argue that some litigation on Benedictin in the US gives an example of the occurrence of a false positive. According to them, the evidence of the harmfulness of these products presented during the litigation was based on inconclusive studies. Although mainly unsuccessful for the plaintiffs, the litigation nonetheless would have led to a flood of claims, raised legal costs above $100 million and resulted in the withdrawal of the respective products from the market.Footnote ⁴⁶ Others, however, stress that the absence of conclusive scientific studies and evidence does not prove the safety of a product, and hence is not a valid reason for dismissing liability. They even argue that the US Supreme Court in its Daubert case lawFootnote ⁴⁷ accepted a too strict and ill-founded standard for the assessment whether the parties are allowed to present scientific evidence to the jury for proving causation. From their perspective, these standards for admitting evidence raise considerable hurdles for successful toxic tort litigation in general. The legal risk of scientific uncertainty and the risk of having the evidence rejected are consequently primarily borne by the plaintiffs,Footnote ⁴⁸ which subsequently could lead to under-deterrence.

Analogously, a lack of empirical evidence about the extra-judicial effects of tort adjudication makes it difficult to predict the potential effects of an intended ruling. For example, in the context of nanotechnology contradicting arguments have been made about the behavioural effects of the threat of liability. Some argue that less liability provides an incentive for more precaution,Footnote ⁴⁹ while others, on uncertain and unknown risks in general, favour a strict liability regime since it would provide actors with an incentive to do research.Footnote ⁵⁰

1 Bipolar and multipolar risk reasoning

Bearing in mind the previous section, it becomes clear that when deciding upon a matter that involves uncertain risks, courts have to determine which party to the proceedings bears the risk of the potentially involved errors, and in the case of unclear law modify the applicable legal concepts accordingly. Courts could do so through bipolar and multipolar reasoning.Footnote ⁵¹ Bipolar reasoning, which is central tort law reasoning, relates to the allocation of risks and uncertainties and the potential errors between the litigating parties. To a significant extent this allocation is determined by the applicable procedural rules on the burden of production of evidence and the burden of proof, and the applicable substantive rules.

2 The (increasing) relevance of multipolar considerations

Under multipolar reasoning a court also takes regulatory effect into account.Footnote ⁵² Multipolar issues – or as Fuller and Winston call them, polycentric issuesFootnote ⁵³ – might be present in a case depending on among other things the litigated issue, the framing of the problem and the type of proceeding and the remedy sought.Footnote ⁵⁴

First, as Cane argues, judicial rule-making “by its very nature involves extrapolating from the particular to the general.”Footnote ⁵⁵ This characteristic of judicial reasoning especially raises problems if the interests of non-represented groups are involved: “what courts have more difficulty doing is taking account of the interests of third parties who do not belong to either of the classes represented by the opposing litigants.”Footnote ⁵⁶

Secondly, some legal proceedings are more “multipolar by nature”. Proceedings such as collective redress for mass harm, test cases, public interest litigation and cases on public authority liability by nature transcend the interests of the litigating parties. The tendency to use private enforcement as a regulatory device and the increased possibilities of collective redress in mass torts in several countries, make it likely that civil cases by nature involve larger groups within society. Equally important in this respect is that some litigants, such as repeat players (eg insurers) and interest groups, initiate litigation specifically for reasons of its regulatory effects. For instance, in public interest litigation, the societal impact of litigation is often equally important to the plaintiffs as the legal implications of the verdict: their main aim is to change the societal status quo. Initiators of test cases also aspire to achieve clarity on the law or to stretch the boundaries of the law, among other things, to be able to adjust litigation strategies or to gain leverage to force an industry to change its behaviour. Besides, given the potential societal impact of decisions that relate to mass harms and the potential scope of such decisions, some scholars argue that courts cannot ignore the social consequences of their judgments in these situations.Footnote ⁵⁷

Third, as has been widely observed by scholars from the civil law and common law world, courts do already take regulatory considerations into account, especially if the applicable law is not clear and courts are engaging in law making.Footnote ⁵⁸ In England and Wales, for example, policy-arguments play an important role in examining whether a duty of care has been breached.Footnote ⁵⁹ In addition, in several countries courts considered among other things floodgate concerns and the consequences of public authority liability on government funding as a reason for reluctance in accepting liability,Footnote ⁶⁰ used the potential deterrent effects of accepting variations on the theory of proportionate liability for justifying its acceptance,Footnote ⁶¹ and denied the applicability of the tort of public nuisance to societal risks on the basis of regulatory considerations.Footnote ⁶² In many instances, however, and perhaps as a consequence of controversy about the empirical validity of such concerns,Footnote ⁶³ the exact meaning of these considerations remains under-expressed and hence camouflaged. Cane even argues that in the common law world multipolar reasoning is largely based on “untested speculation and intuition.”Footnote ⁶⁴ Similar arguments have been made in civil law jurisdictions such as The Netherlands.Footnote ⁶⁵

Considering the clarity, the transparency and acceptability of judicial law making, one justifiably can require courts to be at least explicit about the (legal) implications of these considerations.Footnote ⁶⁶ Courts should reason either why regulatory considerations should be ignored, acknowledge that a regulatory argument does not rest on actual knowledge or why these considerations are instead a valid reason for denying or accepting liability.

When addressing multipolar considerations courts can operate with restraint and engage in minimalistic decision-making or embrace the regulatory effects of tort law and hence engage in “regulatory reasoning”.Footnote ⁶⁷ Minimalistic reasoning means that the court gives ruling upon the particular matter at hand and leaves as much as possible undecided, thereby limiting the legal scope of a specific decision, specifically about and because of the broader implications of that ruling.Footnote ⁶⁸ This does not, however, mean that minimalistic decisions could not have regulatory relevance. While courts might not consider themselves to be the proper institution to evaluate the regulatory implications of a ruling, a minimalistic judgment can still bring attention to the need for risk regulation.Footnote ⁶⁹ Minimalistic decisions, for instance, can signal towards the parties, the relevant industry or even the government the need for more sound information and research into the potential consequences of an intended ruling. When engaging in regulatory reasoning courts explicitly substantiate their verdict with regulatory considerations and the allocation of potential errors of a decision between third parties.

3 Bipolar restraints on multipolar reasoning

If they want to engage in multipolar risk reasoning, next to adjudicative factsFootnote ⁷⁰ courts are also in need of social factsFootnote ⁷¹ and legislative factsFootnote ⁷² that place the dispute in its societal and regulatory context. One should, however, bear in mind that the bipolar nature of tort law limits the availability of social and legislative facts. The perceived or even real presence of these deficits in a specific case subsequently determines (or better: restrains) the court’s possibilities to consider multipolar considerations,Footnote ⁷³ which can lead to empirical errors in the (multipolar) reasoning.Footnote ⁷⁴

First, the principles of party autonomy and judicial passiveness, that are central to tort law, bring with them that the litigating parties determine when to litigate, the subject matter of the litigation and the facts to consider.Footnote ⁷⁵ In other words, civil courts are passive receivers of information and might, therefore, have limited knowledge, methods and tools to evaluate what the (regulatory) effects of a ruling are probably going to be for non-litigants.Footnote ⁷⁶ While the parties to the proceedings have a strong incentive to bring forward adjudicative facts, the availability of social and legislative facts, of course, depends on the nature of the litigating parties (eg repeat players versus one shotter) and their interests and tools to generate such information. Some types of litigants, such as the single worker exposed to asbestos, might lack the tools, institutional support, and financial means to generate social and legislative facts.Footnote ⁷⁷ Moreover, even if the parties present the social and legislative facts needed, they have a strong incentive to present and interpret this information in line with their interests. This can be troubling for courts if there are several valid ways of interpreting the information.

Second, most civil judges are legal generalists and do not necessarily have the qualification and specialisation to assess (complex) scientific information.Footnote ⁷⁸ Consequently, they might have to rely on the parties and/or have to call for expert opinions to evaluate scientific information, for instance on the characteristic of the social context in which the risk is present (what is the chance of exposure to nanoparticles in several situations?).Footnote ⁷⁹ This lack of official expertise can especially become problematic when there is no clear information available at all.Footnote ⁸⁰

Lastly, it is hard for courts to deal with multipolar issues in a systemic fashion.Footnote ⁸¹ Courts cannot initiate legal proceedings themselves,Footnote ⁸² which restricts their possibility to change legal norms appropriately. In addition, potential plaintiffs might lack the interests or resources to initiate proceedings, and even if they start proceedings, courts decide on a case by case basis. In the end courts might therefore move too slowly to keep up with the pace of changes in society that require changes in the law. Changes in the law might specifically be needed when scientific insights on a specific risk have changed and it becomes clear that the applicable rule is not adequate anymore, which particularly can be the case in situations of rapidly changing technologies. Whether courts can play a regulatory role in such circumstances, and hence update the applicable norms, depends on several parameters that influence the possibility and willingness of actors to initiate litigation, such as legal chances of success in court, litigation costs, rule on cost awards, recoverable damages and financial incentives to initiate proceedings,Footnote ⁸³ and the level of organisation of interest groups. The presence and nature of these circumstances are for a considerable part influenced by the litigation culture of the relevant jurisdiction,Footnote ⁸⁴ and civil courts are relatively limited at the controls of most of these parameters.

2 Uncertain risks and the required conduct

Under negligence-based claims, one has to assess whether the defendant took more risk than reasonably acceptable. According to Article 4:102 of the European Principles of Tort law this examination “depends, in particular, on the nature and value of the protected interest involved, the dangerousness of the activity, the expertise to be expected of a person carrying it on, the foreseeability of the damage, the relationship of proximity or special reliance between those involved, as well as the availability and the costs of precautionary or alternative methods.”Footnote ⁸⁶

How these viewpoints work out in relation to uncertain risks is unclear,Footnote ⁸⁷ and their application is particularly challenging if there is a combination of uncertainty about the existence of a risk and the effectiveness of preventive measures. In that instance, the question is whether an actor is reasonably allowed to engage in certain behaviour without knowing its potential adverse effects on the one hand, but often knowing that the behaviour has benefits on the other. Also, it comes down to the question whether the defendant is obliged to take a measure whose effectiveness is not (yet) proven. Accepting a duty of care in this situation involves the error of unnecessarily taking precautions. Denying it would mean that the victim potentially is deprived of his safety and possibly exposed to a risk. Paradoxically, a lack of scientific social facts and legislative facts makes it difficult to determine the chance(s) that one of each will occur.

The precautionary principle could give the normative framework for determining the required behaviour.Footnote ⁸⁸ The principle has a negative and positive element. The negative element means that a lack of full scientific certainty about a risk is no valid reason for postponing (cost-effective) measures to manage these risks.Footnote ⁸⁹ The positive element prescribes proactivity: when there is a plausible concern for the existence of a severe risk, operators that engage in uncertain risk behaviour should take precautions to avoid or diminish the possibility of harm.Footnote ⁹⁰ The principle underlines the insight that the absence of scientific evidence of the existence of a risk cannot be seen as evidence of the absence of a risk, and resonates the idea that actors have to take responsibility for the adverse effects of the uncertainties about the risks created by their behaviour. Particularly in the course of an asymmetrical power relationship between the risk subject and risk creator and the appearance of the vulnerability of the risk subject one could embrace its application. When present, or perhaps merely when perceived, asymmetries as meant above provide the courts with good reasons and justifications to embrace the precautionary principle in a specific bipolar relationship.Footnote ⁹¹

Still, the assessment of the potential regulatory effects of accepting the principle, is difficult due to a lack of clear scientific information about the risks involved. There is, however, a way to decrease the need for information but still amplifying norms and signal the legally-required way of dealing with the uncertain risk.Footnote ⁹² Courts could abstract from the complexity of a risk problem and determine the applicable responsibilities in rather general terms, for instance by embracing the precautionary principle and amplifying the precautionary norm that with the creation of uncertain risks, also responsibilities for the uncertainties arise.Footnote ⁹³ As a consequence, courts attribute the risks of error as a result of a lack of information deficits to the defendant that is responsible for the “creation” of uncertainty, as it is then his responsibility to decide how to implement these notions of responsibility. From a regulatory perspective, one could favour this approach if (one assumes that) the defendant has more information about the risks and, inter alia, has more resources and possibilities for engaging into research at its disposal than the defendant (or the government) has. The point is that, although legislative information that shows the effectiveness of such a ruling is not available, the potential errors that ensue from this lack of information could be attributed to the defendant and are not necessarily a reason for judicial restraint.

3 Specific and generic uncertainty and cause-in-fact

Many (uncertain) risk of industrial society, such as asbestos, tobacco, climate change risks, and potential risks related to biotechnology and nanotechnology are characterised by a complex system of causal indeterminacy. Of these causal complexities, especially generic and specific causation uncertainty raise evidential challenges. Generic causation uncertainty refers to the existence of a risk as such and hence to the level of uncertainty about whether an act can cause harm at all. For example, can exposure to a nanoparticle cause cancer? In the situation of specific causation uncertainty, the question is whether, and to what extent, a specific act has caused a specific harm. Did exposure to asbestos cause the victim’s cancer, or was it the victim’s smoking? When faced with such uncertainties, tort law determines which of the parties have to overcome the evidential problems and hence bears the risk of not being able to prove a causal connection or to refute its existence.

The traditional test for examining cause-in-fact is the but-for test, which means that an examination has to be made whether the existence of the harm would have occurred but for the existence of the behaviour of the defendant.Footnote ⁹⁴ However, under this test the plaintiff, who as a general rule bears the burden of proof, will not be able to prove a causal connection between the alleged wrongdoing and their harm due to causal indeterminacy and the accompanying evidential problems.Footnote ⁹⁵ A false negative, ie no liability for wrongful risky behaviour, is the likely consequence and the tort system might lead to under-deterrence.

In many instances of specific causation uncertainty courts showed willingness to offer recourse against the wrongful behaviour by the defendant even though the exact consequences of that behaviour could not be proven. They did so by introducing mechanisms for partly attributing the evidentiary problems and the related risks of error to the defendant, such as the lowering of standards of proof, the introduction of evidentiary presumptions, reversal of the burden of proofFootnote ⁹⁶ and the acceptance of the theory of proportionate liability and a loss-of-chance.Footnote ⁹⁷ Courts endorsed variations on these theories with respect to several variations on specific causation uncertainties covering inter alia liability for toxic substances, environmental harm, medical liability and product liability.Footnote ⁹⁸

Bipolar reasoning gives a strong justification for the introduction of these mechanisms. The defendant’s wrongful creation of serious health risks should not be left unsanctioned at the costs of the victim due to evidentiary problems.Footnote ⁹⁹ As Nolan put it, the inadequacy of the traditional causation requirements for dealing with complex industrial risks should work “to the detriment of the negligent defendants rather than the blameless victim(s).”Footnote ¹⁰⁰ Regulatory arguments could also be made to favour this approach.Footnote ¹⁰¹ Causation uncertainties undermine the plaintiff’s chances of success in court which consequently also causes under-deterrence:Footnote ¹⁰² the defendants’ wrongdoing is left unsanctioned and a signal to the relevant group of actors is given that their legal duties of care have limited practical relevance. Unsurprisingly, courts explicitly justified relieving the causation requirements by referring to the incentives they create for actors to confirm their legal duties.Footnote ¹⁰³

Some scholars question this stance on regulatory grounds, arguing that the boundaries of tort’s flexibility are reached in the context of scientific uncertainty about risks. Their main point is that it would not be appropriate to loosen traditional causation requirements to distribute specific uncertainty elsewhere without thought,Footnote ¹⁰⁴ risking opening the floodgates or creating negative economic effects, particularly if applied to systemic risks, such as climate change risks.Footnote ¹⁰⁵ Accepting this argumentation requires either minimalistic decision-making or the overruling of established case law.

The justifiability of relieving causation standards in relation to generic causation uncertainties is more debatable. One might argue that generic causation uncertainties and the risks of error that come with them, should also be borne by the actor that is responsible for the activity that brought along these uncertainties.Footnote ¹⁰⁶ The most far-reaching mechanism for implementing this idea is shifting the burden of proof to the defendant, who then has to prove that his behaviour was not capable of causing the harm at all or did not cause the harm in that specific case. For instance, a producer of nanoparticles then has to prove these particles do not impose (unacceptable) risks. The defendant, however, will be confronted with the same difficulties as the plaintiff when refuting the existence of a generic causal connection. Such a scheme thus would come close to liability without causation,Footnote ¹⁰⁷ and for this reason will be at odds with the very fundaments of tort law.Footnote ¹⁰⁸

Unlike cases involving specific causation uncertainty, where the causal connection between the risk and the defendant’s wrongful behaviour is known in a generic sense, in situations of generic uncertainty the wrongdoing on the side of the plaintiff may not provide the justification for shifting the potential of errors to the defendant. Although the precautionary principle gives the normative framework for determining the standard of care in relation to uncertain risks, its relevance for examining causation and hence the distribution of damages is contentious, for at least three reasons. First, the principle’s ethical foundation roots in a Kantian duty-based theory and does not touch upon liability mechanisms.Footnote ¹⁰⁹ The ethic of precaution is primarily concerned with the protection of a vulnerable world against our potential to do catastrophic and irreversible harm, not with restoration or compensation.Footnote ¹¹⁰ Second, and subsequent to the preceding, its legal reception took place in areas of public law that are concerned with ex-ante risk regulation and management, and ultimately, the prevention of unacceptable harm, again not compensation. Third, the relevance of the principle for causation issues is contested because of its potential societal consequences.

Proponents of shifting the legal risks of generic uncertainty to the defendant would argue that it creates an incentive for deterrence in the context of uncertain risks.Footnote ¹¹¹ Internalisation of the costs of generic uncertainty would create an incentive for actors to reduce the uncertainty or to take safety measures. In this way, tort law theoretically becomes an instrument to implement the precautionary principle and amplifies its rationale that actors should not be allowed to fully transfer the costs of uncertainty that come along with their behaviour to society and risk subjects. Others, however, stress the negative societal effects of this approach. According to them it would lead to an increase in ill-founded claims, raise considerable insurability issues and, lastly, leads to excessive care. Consequently, innovation would be hindered and slowed down, although one could argue that exactly this effect would be the goal of accepting the principle in this situation. It is difficult to assess these arguments on empirical grounds.Footnote ¹¹² Nonetheless, the fact that generic uncertainty exists in relation to a wide range of situations,Footnote ¹¹³ gives some indications on the scope of such a ruling and the difficulties courts might face in delineating such a rule.