Whether a case proceeds as a class action usually matters more than who is right. Certification converts individually modest claims into aggregate exposure, and it is decided on a demanding record.
The threshold requirements are familiar: the class is so numerous that joinder is impracticable; there are questions of law or fact common to the class; the representative’s claims are typical; and the representative and counsel will adequately protect the class.
Commonality is where cases turn. It is not enough that class members share a grievance; there must be a common contention capable of classwide resolution — one whose determination will resolve an issue central to each claim in one stroke. A policy applied uniformly satisfies this; a set of individualised decisions by different managers usually does not.
Predominance and superiority apply to damages classes: common questions must predominate over individual ones, and a class action must be the superior method. Individualised damages do not automatically defeat predominance, but a case requiring person-by-person inquiry into liability generally does.
The record. Certification is decided after a rigorous analysis that may overlap the merits, usually with expert evidence on both sides about whether common proof is possible.
Consequences. An order granting or denying certification is frequently subject to immediate discretionary appeal, and it is almost always the moment a case either settles or ends.