Explicit legal provisions or case law precedents accompanying competition law frameworks generally determine who has the obligation to produce factual and legal evidence to establish the existence of (potentially) anticompetitive behaviour. Those provisions or precedents are necessary tools to ensure that competition law investigations take place in a predictable manner. In their essence, burden of proof norms or principles determine which party bears the risk of facts remaining unresolved or allegations unproven (see also Opinion of Advocate General Kokott in CJEU Case C-8/08, T-Mobile, EU:C:2009:110, para 80). Competition law frameworks therefore classically determine who has to prove what in general terms. In addition, the courts generally recognise short-cut rules to fast-track certain cases and to allow infringements/liability to be established on the basis of certain assumptions or evidentiary presumptions. Those presumptions may in turn shift the burden to prove the absence of anticompetitive behaviour or effects on a different party.
The general principle that the claimant bears the burden of producing relevant evidence (actori incumbit probatio) stands in both EU and U.S. law. In European Union law, Article 2 of Council Regulation 1/2003 states that the burden of proving an infringement of Article 101(1) or of Article 102 of the Treaty shall rest on the party or the authority alleging the infringement. The undertaking or association of undertakings claiming the benefit of Article 101(3) of the Treaty shall bear the burden of proving that the conditions of that paragraph are fulfilled. In merger control, it follows from Articles 2(2) and (3) of Regulation 139/2004 that the Commission bears the burden of proving that an envisaged concentration would produce a significant impediment to effective competition (see also General Court, T-399/16, CK Telecom, EU:T:2020:217, para 107). In U.S. antitrust law, it is in principle also the claimant who needs to adduce the relevant evidence. In per se infringements, the government or plaintiff needs to produce evidence that the behaviour falls within one of the per se categories (U.S. Supreme Court, Ohio v American Express, 138 S. Ct. 2274 (2018), 9). The same goes for merger review under Section 7 of the Clayton Act. In such cases, “[t]o establish a prima facie case, the Government must (1) propose the proper relevant market and (2) show that the effect of the merger in that market is likely to be anticompetitive” (FTC v. Penn State Hershey Med. Ctr., 838 F.3d 327, 337-38 (3d Cir. 2016).
Despite those general rules or principles, courts have come to accept so-called short-cut rules and evidentiary presumptions that in practice result in alleviating or shifting the actual evidentiary burden ordinarily falling upon the claimant.
Short-cut rules allow a claimant to assume that anticompetitive behaviour is in place on the basis of proof of certain types of behaviour or other elements, without having to show more conclusively the anticompetitive object or effect of the behaviour in question. An example in EU law is the assumption that pricing below average variable costs by a dominant undertaking is anticompetitive (CJEU, Case C-62/86, Akzo, EU:C:1991:286) or the assumption that certain behaviour meets U.S. per se standards. Short-cut rules alleviate the burden of proof resting on the claimant, who can successfully bring a claim based on evidence assuming anticompetitive behaviour. The defendant is generally unable to refute or contest the claim where such assumptions apply.
Evidentiary presumptions allow the decision-maker to infer, on the basis of evidence offered, that anticompetitive behaviour is present. The defendant may then proceed to rebut those presumptions on the basis of more specific evidence to the contrary. Examples of evidentiary presumptions are the presumption of parental liability (CJEU, C-97/08 P, Akzo, EU:C:2009:536 ), the presumption that contacts between undertakings behaving in a parallel fashion allow the inference of the existence of a concerted practice (although not automatically an anticompetitive practice) under Article 101 TFEU (CJEU, C-49/92 P, Anic, EU:C:1999:356, para 121) or the presumption of dominance on the basis of (excessively) large market shares. The U.S. rule of reason framework also establishes a burden-shifting evidentiary presumption framework. According to the U.S. Supreme Court, ‘the plaintiff has the initial burden to prove that the challenged restraint has a substantial anticompetitive effect that harms consumers in the relevant market. […] If the plaintiff carries its burden, then the burden shifts to the defendant to show a procompetitive rationale for the restraint. […] If the defendant makes this showing, then the burden shifts back to the plaintiff to demonstrate that the procompetitive efficiencies could be reasonably achieved through less anticompetitive means’ (U.S. Supreme Court, Ohio v American Express, 138 S. Ct. 2274 (2018), 9-10). Evidentiary presumptions in practice thus shift the evidentiary burden from the claimant to the defendant. The latter will have to offer the evidence of absence of anticompetitive behaviour or of procompetitive advantages justifying and outweighing anticompetitive effects.
Although short-cut rules and evidentiary presumptions exist in both EU and U.S. law, two factors currently mitigate against their unbridled expansion. First, at a more individual level, shifting the burden to or disabling a defendant to prove innocence is difficult to align with fundamental rights such as the presumption of innocence. Someone accused of anticompetitive behaviour cannot simply be held liable or condemned on the basis of assumptions against which no reasonably justified defence can be introduced. Second, and more generally, competition/antitrust systems increasingly pay attention to effects-focused analysis: in order to prove anticompetitive behaviour, the anticompetitive effects of such behaviour on the structure and operations of the market need to be established to a sufficient extent. Short-cut rules and evidentiary presumptions allowing fast-track analyses make it easier for claimants to establish liability without fully proving the presence of such effects. It appears that reliance on those shortcuts or presumptions to meet the standard of proof is no longer unequivocally tolerated by courts. As a result, an apparent overall decline of both short-cuts and evidentiary presumptions in favour of a more coherently applied actori incumbit probatio burden of proof standard can be seen in both EU and U.S. (case) law (by way of recent example, General Court, T-286/09 RENV, EU:T:2022:19, para 165-166).
