In reaching its decision on the carriage dispute, the CAT noted the guidance set out in the Court of Appeal's judgment in Evans v Barclays Bank plc:[4]
(i) The CAT should apply a test of "suitability" when considering each application and the discretion of the CAT in doing so is broad and multifaceted.
(ii) The CAT is expert at how proceedings play out at the "nuts and bolts" level and can form a view on the weight to be attached to the various considerations.
(iii) The CAT may decide on carriage without the need to take account of the merits of either case.
(iv) The fact that one PCR merely has a broader claim than the other is not an indication that that claim is preferable.
(v) The question of which claim was the first to file is largely an irrelevant factor.
With this guidance in mind, the CAT considered that the "key differentiator" between the two applications was the expert evidence which had been adduced for the purposes of demonstrating that the applications met the Pro-Sys[5] test in the sense that the proposed expert methodologies offered a "realistic prospect of establishing loss on a class wide basis". Indeed, central to the CAT's assessment as to which application was more suitable were the methodologies proposed by each PCR in relation to: (i) the proof of the abuse; and (ii) the quantification of the overall loss suffered by the consumers.
While each party's expert had successfully cast doubt on the other's methodology, neither had successfully persuaded the CAT that the other's was bound to fail at certification.
In deciding between the two rival methodologies, the CAT formulated a test by way of two key (interrelated) questions, namely:
1) Which methodology was "clearly and distinctly" better suited at articulating and resolving the claims that the PCRs wish to bring.
2) Whether there was a difference in the practical workability of the methodologies and, taken at its most extreme, whether it can be fairly said that one or the other of them simply "will not work".
In addressing the first question, the CAT determined that the methodology of Mr Hammond's expert is better suited to resolving the claim as the proposed counterfactual which involves re-running the algorithms without the abuses as alleged, is more closely aligned to the alleged abuse. In contrast, the CAT viewed Ms Hunter's expert's methodology (which sought to ascertain consumer preferences for the purposes of establishing an appropriate counterfactual), as not aligning closely enough with the "true counterfactual" (i.e. the operation of Amazon's algorithm without the alleged abuse).
As to the second question, in determining the practical workability of Mr Hammond's expert's methodology, the CAT was satisfied it was "sufficiently workable" because it was clear from the methodology that the expert had considered the difficulties and how they could be overcome. Further, while Ms Hunter's expert expressed scepticism in regard to Mr Hammond's expert's methodology, Ms Hunter's expert stopped "well short" of saying that Mr Hammond's expert's methodology was unworkable.
The CAT therefore ruled that Mr Hammond was most suitable to act as the proposed class representative and he may therefore proceed to the certification stage.[6]
While the CAT considered the issues of the differing class definitions, differing claim periods and the time at which each of the applications were filed, the CAT did not attach weight to these considerations for the purposes of determining the carriage dispute.
As to Ms Hunter, although the CAT ruled in favour of Mr Hammond, it decided to stay her application on the basis that it was “well put together" and has "simply come second in a hard-fought race.” In the event Mr Hammond's application for certification fails or is otherwise revoked, the stay on Ms Hunter's application could be lifted and her application could proceed to certification.
The CAT did, however, stress that, in the case of a "hopeless" application, an application that lost on the issue of carriage ought to be dismissed.