Chapter 4 - § 4.2 • PROHIBITED CONDUCT AND PROOF OF SAME

• Jurisdiction: Colorado

§ 4.2 • PROHIBITED CONDUCT AND PROOF OF SAME

§ 4.2.1—Disparate Treatment Claims

A violation of the ADEA occurs when a covered employer discriminates due to age in hiring, termination, compensation, and other terms, conditions, and privileges of employment. 29 U.S.C. § 623(a)(1). An ADEA plaintiff, at least in the private sector, must prove by a preponderance of the evidence that age was the "but-for" cause of the challenged employer action. Gross v. FBL Fin. Servs., Inc., 557 U.S. 167 (2009); see also Harley v. Potter, 416 F. App'x 748, 751 (10th Cir. 2011) (reaffirming rule that age must be the but-for cause of the challenged adverse employment action, but reiterating that the "but-for" standard does not require plaintiff to show age was employer's sole motivating factor; employer may be liable under ADEA if other factors contributed to its taking an adverse action, so long as age was factor that made a difference). In this regard, ADEA cases differ from Title VII cases, which allow the "mixed motive" standard set forth in cases such as Price Waterhouse v. Hopkins, 490 U.S. 228 (1989). However, the Supreme Court has granted certiorari to determine whether the "mixed motive" standard rather than the but-for standard applies to federal-sector ADEA claims, on the grounds that the federal-sector portion of the ADEA states that federal employment decisions "shall be made free from any discrimination based on age," 29 U.S.C. § 633a(a), whereas the private-sector portion of the ADEA interpreted in Gross only prohibits discrimination "because of" age, 29 U.S.C. § 623(a)(1). Babb v. Wilkie, 139 S. Ct. 2775 (2019).

The burden of persuasion to prove a disparate treatment claim under the ADEA remains with the plaintiff, whether presenting direct or circumstantial evidence of discrimination. Gross, 557 U.S. at 177. The Tenth Circuit has concluded, however, that the McDonnell Douglas burden-shifting analysis continues to apply to ADEA claims based upon circumstantial evidence after Gross. Jones v. Okla. City Pub. Sch., 617 F.3d 1273 (10th Cir. 2010). In Jones, the Tenth Circuit stated that the McDonnell Douglas framework shifts only the burden of production, not the burden of persuasion and, therefore, is not at odds with Gross. (Note: Numerous bills have been introduced in Congress since 2009 to overturn the Gross "but-for" standard for private sector age discrimination claims and return to a "mixed-motive" standard but, to date, none have passed.)

Additionally, similar to Title VII, a plaintiff may recover under the ADEA if he or she proves that he or she was subjected to a hostile work environment on the basis of age. MacKenzie v. City & County of Denver, 414 F.3d 1266 (10th Cir. 2005). To be actionable, the harassment based on age must be sufficiently severe or...