Judge Richard Posner has always been an independent thinker, something he has proven in the last year as, despite his economically conservative credentials (which would lead one to presume a possible defense bias), he authored a number of arguably pro-plaintiff class certification opinions, particularly his twin opinions in the controversial case Butler v. Sears Roebuck & Co. (2012) (2013) And so it is noteworthy that, despite his ruling in Sears, he has also authored the opinion in Parko v. Shell Oil Co., No. 13-8023, 2014 U.S. App. LEXIS 1018 (7th Cir. Jan. 17, 2014).

Parko involves an environmental class action filed by property owners in Roxana, Illinois against several oil companies that allegedly ran a refinery that leaked benzene into the surrounding groundwater. The plaintiffs sought damages for the reduction in their property values. The district court certified the class, and the defendants appealed, arguing that it had not found that the common question it identified–whether the defendants had caused benzene leaks–predominated over individualized issues of causation and damages.

The Seventh Circuit took the appeal to

clarify class action law, see Blair v. Equifax Check Service, Inc., 181 F.3d 832, 835 (7th Cir. 1999), with respect to district courts’ responsibility to perform a "rigorous analysis" before determining that issues common to the class predominate over issues that differ among the individual class members.

Judge Posner reiterated the same definition of predominance that he used in Butler.

Predominance is a qualitative rather than a quantitative concept. It is not determined simply by counting noses: that is, determining whether there are more common issues or more individual issues, regardless of relative importance.

But where–in that case–he decided that the presence of fully-functioning washer-dryers did not predominate over arguably common questions, here he reversed the lower court’s certification. The difference? The Butler court had engaged in the proper rigorous analysis, whereas here,

The district judge … treated predominance as a pleading requirement. He thought it enough at this stage that the plaintiffs intend to rely on common evidence and a single methodology to prove both injury and damages, and that whether the evidence and the methodology are sound and convincing is a question going to the strength of the plaintiffs’ case and should be postponed to summary judgment proceedings or trial. But if intentions (hopes, in other words) were enough, predominance, as a check on casting lawsuits in the class action mold, would be out the window. Nothing is simpler than to make an unsubstantiated allegation. A district judge may not "refus[e] to entertain arguments against respondents’ damages model that bore on the propriety of class certification, simply because those arguments would also be pertinent to the merits determination." Comcast Corp. v. Behrend, supra, 133 S. Ct. at 1432-33. The judge should have investigated the realism of the plaintiffs’ injury and damage model in light of the defendants’ counterarguments, and to that end should have taken evidence. For if the defendants are right, there is no common issue, only individual issues that will vary from homeowner to homeowner …

(Emphasis added.)  There are two takeaways here for defense lawyers. One, even our most prolific judges are not always easy to predict with a partisan (pro-plaintiff v. pro-defendant) analysis. Two, stress the evidence. Just because some plaintiffs will not proffer it does not make it irrelevant to certification.