To establish the defense of a good faith seniority system, [defendant] must prove both of the following by a preponderance of the evidence:
Second: That [defendant’s] [challenged employment action] was consistent with its seniority system.
COMMENT
The ADEA permits disparate treatment “to observe the terms of a bona fide seniority system that is not intended to evade the purposes of this Act, except that no such seniority system shall require or permit the involuntary retirement of any individual... because of the age of such individual.” 29 U.S.C. § 623(f)(2)(A). Thus the seniority system will be invalid if it is dependent on age rather than seniority. See also Hazen Paper Co. v. Biggins, 507 U.S. 604, 616 (1993) (rejecting a claim of age discrimination to the extent the challenged employment practice was based on the plaintiff’s seniority not his age).The Supreme Court has held that challenges to the effects of bona fide seniority systems may not be based upon assertions of disparate impact; rather, a plaintiff must prove intentional discrimination. See International Brotherhood of Teamsters v. United States, 431 U.S. 324, 352-56 (1977). See also Hiatt v. Union Pacific R.R., 65 F.3d 838, 842 (10th Cir. 1995) (challenges of age discrimination to bona fide seniority systems must rest upon claim of disparate treatment rather than disparate impact).
