The key litigated issue in Amgen, Inc. v. Connecticut Retirement Plans and Trust Funds focused on whether a plaintiff must prove materiality of the alleged misrepresentations and omissions to certify a class in a case brought under Section 10(b) of the Securities Exchange Act of 1934 (Section 10(b)) and Securities Exchange Commission Rule 10b-5 (Rule 10b-5).

The appellee in this action, institutional investor Connecticut Retirement (the plaintiff in the district court matter), brought a private action against Amgen, Inc., of which it was a shareholder. Connecticut Retirement alleged that Amgen made misrepresentations and omissions in public disclosure statements, violating Section 10(b) and Rule 10b-5, and that it had relied on these misstatements in its purchase of Amgen's stock. It sought class certification under FRCP 23(b)(3) on behalf of all investors who had purchased Amgen stock during the period of misrepresentation.

The district court granted class certification. After granting Amgen's request to take an interlocutory appeal on this issue, the US Court of Appeals for the Ninth Circuit affirmed the district court's order and rejected Amgen's arguments that the district court erred by certifying the proposed class without first requiring Connecticut Retirement to prove the materiality of the alleged misrepresentations and omissions. Amgen then petitioned for certiorari, which the US Supreme Court granted.

In its February 27, 2013 decision, the Supreme Court held that proof of materiality is not needed to ensure that questions of law or fact common to the class will predominate over questions affecting only individual members because:

The Supreme Court held that Connecticut Retirement should therefore not be required to prove the materiality of the alleged misrepresentations and omissions to obtain class-certification. This proof should properly be addressed at trial or through a summary judgment motion.

The decision in Amgen ends a circuit split that developed over the plaintiff's requirement to prove the element of materiality to certify a proposed class in Section 10(b) and Rule 10b-5 cases. The Supreme Court's decision ensures that all federal courts will treat these situations in a uniform manner.