Iudex Non Calculat? Judges and the Magnitude of Mass Litigation from a Behavioural Perspective

Mass harm situations caused by corporate misbehaviour (e.g. anticompetitive practices, misleading market information), defective products, harmful pharmaceuticals, accidents or environmental disasters nowadays tend to multiply and create new challenges not only for legal actors, but also for society at large. In its 2013 Recommendations, the EU Commission highlighted that 'a key role should be given to courts in protecting the rights and interests of all the parties involved in collective redress actions as well as in managing the collective redress actions effectively'. The role of judges therefore turns out to be essential: they are expected to behave as watchdogs scrutinizing the overall admissibility of mass claims, as active case managers ensuring that cases indeed make orderly progress, and as shepherds ensuring that all interests at stake are sufficiently protected. Importantly, judges are thus expected to be neutral, unbiased and robust agents, while assuming heavy responsibilities under a considerable burden. A key issue to be explored remains the influence of the 'mass context' which may possibly lead judges to depart from policymakers' expectations. Interestingly, the mass context is nowadays an element often discarded by judges themselves. Yet, in the context of mass litigation, cases involve and consolidate in one lawsuit potentially hundreds of represented claimants who have suffered a similar harm. The magnitude of the case -- that is the number of people involved and/or the size of the loss at stake -- is therefore likely to be considerable. Even though judges discuss and exchange with a limited number of protagonists during hearings -- for instance with representative bodies such as associations or leading counsels -- judges must preserve the interests of absent parties. They thus take most of their decisions in the shadow of numerous represented plaintiffs, or in other words, in the shadow of number. Behavioural studies have shed important light on ways groups are perceived by external observers, or on the impact of number and size on information gathering and processing. By referring to this branch of literature, this paper aims at investigating in greater details the effect of case magnitude on decision-making