Jackson v. Unocal Corp., 262 P.3d 874

Class action in Colorado alleging asbestos contamination from removal of a buried oil pipeline owned by Unocal; easement properties contained asbestos wrap; removal occurred 1996–1998 leaving asbestos fibers on easement properties.
Plaintiffs sought certification under C.R.C.P. 23(b)(3) for Easement Property and Contiguous Property Classes seeking damages for diminution of land value, remediation, and loss of use.
Trial court conducted extensive record review, expert depositions, and hearing; court certified both classes finding identifiable class and predominance; trial court rejected screening out merits in resolving disputes overlapping with merits.
Court of Appeals reversed, holding a preponderance-of-evidence standard applied to each Rule 23 requirement and requiring resolution of overlapping expert disputes; also directed examination of affirmative defenses and damages.
Colorado Supreme Court granted review to decide (1) burden of proof standards for Rule 23, (2) whether trial court must assess credibility of expert testimony at certification, (3) whether certification is impermissibly invaded by merits-focused case management.

Issue	Plaintiff's Argument	Defendant's Argument	Held
Burden of proof for Rule 23 requirements	Jackson argues preponderance required.	Unocal argues preponderance required.	No fixed burden; discretion to satisfy requirements suffices.
Credibility review of expert testimony at certification	Spear's and Ganesan's differing opinions should be weighed.	Court must resolve credibility of experts at certification.	Trial court may analyze expert disputes but need not resolve which expert prevails.
Overlap with merits in predominance and defenses	Overlaps with merits should be allowed if resolution aids Rule 23.	Should not resolve merits; should decouple class certification.	Overlap allowed; defenses and merits may be considered to satisfy Rule 23; do not predetermine merits.
Identify class and predominance requirements	Contiguous class defined by five-mile radius supported by diffusion model.	Model assumptions flawed; cannot establish class-wide contamination.	Identifiable class established; common questions predominate; maintain certification.

Amchem Prods., Inc. v. Windsor, 521 U.S. 591 (U.S. 1997) (class actions require careful balancing of issues and commonality)
General Tel. Co. of Southwest v. Falcon, 457 U.S. 147 (U.S. 1982) (rigorous analysis of Rule 23 prerequisites)
Coopers & Lybrand v. Livesay, 437 U.S. 463 (U.S. 1978) (overlap between certification and merits acknowledged)
Wal-Mart Stores, Inc. v. Dukes, 131 S. Ct. 2541 (U.S. 2011) (overlap with merits permissible; certification may involve merits considerations)