I've written before about the inventiveness of plaintiffs counsel when it comes to tobacco and class actions. And Xavier v. Philip Morris USA, 2011 U.S. Dist. LEXIS 42335 (N.D. Cal. Apr. 18, 2011), represents a new chapter in the ongoing tobacco wars.

Xavier was a class acton brought by smokers who were not suffering from any adverse health effects--yet. The named plaintiffs sought to certify a class of

asymptomatic Marlboro smokers and recent quitters who are more than fifty years old and have at least a twenty-pack-year smoking history.

What does twenty-pack-year mean? It represents the number of packs per day multiplied by the number of years the habit persisted, so a twenty-pack-year history could be a pack a day for 20 years, 2 packs a day for 10 years, or some other combination that added up to roughly 146,000 cigarettes. The plaintiffs sought medical monitoring.

Judge Alsup (of Class Settlement Checklist fame) immediately tied the ascertainability problem to the issue of preclusion.

If a class definition includes a requirement that cannot be proven directly, and that depends instead upon each putative class member's feelings and beliefs, then there is no reliable way to ascertain class membership. Without an objective, reliable way to ascertain class membership, the class quickly would become unmanageable, and the preclusive effect of final judgment would be easy to evade.

(Emphasis added.)  In this case, the class was not ascertainable, because determining class membership would require delving into class members' memories of their own conduct:

Thus, while the arithmetic total of an individual's Marlboro-smoking history is an "objective" question, it remains a question, and its answer depends on each individual's subjective estimate of his or her long-term smoking habit. Unlike in many cases, there are no defendant records on point to identify class members. There is no reliable way in which smokers themselves could document their long-term smoking histories.

(Emphasis in original.) Nor would the problems with class members' memories be the only issue in determining class membership. As Judge Alsup explained:

The memory problem is compounded by incentives individuals would have to associate with a successful class or dissociate from an unsuccessful one. Plaintiffs argue that individuals "have little reason to lie given the lack of pecuniary gain" but this order finds to the contrary. For example, long-term smokers of other cigarette brands and long-term smokers who have smoked fewer than 146,000 cigarettes may desire medical monitoring and be tempted to free-ride on relief granted in this action.

Since the class was not ascertainable using objective measures, Judge Alsup denied certification. His opinion is a useful one. In addition to explaining the importance of ascertainability to absent class members, he also expands the analysis a little by pointing out that an "objective" definition needs to rest on reliable data. If class membership relies solely on memory, and there is incentive to fudge, then the membership criteria is not really objective.