Conocophillips Company v. Jeana Parko, 739 F.3d 1083

District court certified a class of about 150 Roxana property owners alleging groundwater contamination from the Wood River Refinery and related polluters.
Plaintiffs allege nuisance and related Illinois torts with damages measured by property value impact from contamination.
Defendants (Shell and ConocoPhillips and subsidiaries) petitioned for interlocutory review under Rule 23(f) seeking reversal or clarification of class certification.
District court analyzed predominance under Rule 23(b)(3) and treated the issue as primarily pleading-based rather than evidence-based.
The court considered potential multiple polluters and variable contamination/damage across class members, raising predominance concerns.

Issue	Plaintiff's Argument	Defendant's Argument	Held
Whether common issues predominate for class certification	Plaintiffs argue common evidence of contamination and damages can bind class	Defendants contend contamination and damages vary by home and polluter, destroying predominance	Certification reversed; predominance not shown
Whether district court properly required a rigorous analysis of predominance	Plaintiffs rely on common methodology to prove injury and damages	Defendants contend need for evidence and testing before certification	Court requires rigorous, evidence-based predominance analysis

Amgen Inc. v. Connecticut Retirement Plans & Trust Funds, 133 S. Ct. 1184 (U.S. 2013) (predominance requires cohesive class; not just more common issues)
Amchem Products, Inc. v. Windsor, 521 U.S. 591 (U.S. 1997) (predominance tests class cohesiveness for representation)
Comcast Corp. v. Behrend, 133 S. Ct. 1426 (U.S. 2013) (requirement to resolve validity of common issues with evidence)
Wal-Mart Stores, Inc. v. Dukes, 131 S. Ct. 2541 (U.S. 2011) (not a pleading standard; need bona fide common questions and evidence)
Gates v. Rohm & Haas Co., 655 F.3d 255 (3d Cir. 2011) (illustrates caveat on multiple polluters and uniform damages)