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January 11, 2021 HUMAN RIGHTS

Comcast and Bostock Offer Clarity on Causation Standard

by Sandra Sperino

For decades, litigants have contested the proper causation standard for federal employment discrimination claims. In Comcast v. National Association of African-American Owned Media, the Supreme Court held that a plaintiff is required to establish “but for” cause to prevail on a claim under 42 U.S.C. § 1981. 140 S. Ct. 1009 (2020).

When an employer discriminates because of sexual orientation or gender identity, it is also discriminating “because of” sex.

When an employer discriminates because of sexual orientation or gender identity, it is also discriminating “because of” sex.


The reasoning in Comcast largely replayed the arguments adopted in University of Texas Southwestern Medical Center v. Nassar, 570 U.S. 338 (2013), and Gross v. FBL Financial Services, Inc., 557 U.S. 167 (2009). In Gross, the Court held that a plaintiff is required to establish “but for” cause to prevail on a claim under the Age Discrimination in Employment Act (ADEA). In Nassar, the Court held that a plaintiff is required to establish “but for” cause to prevail on a retaliation claim under Title VII. This line of cases contradicted the reasoning in Price Waterhouse v. Hopkins that a plaintiff could prevail on a Title VII discrimination claim by showing her protected trait was a motivating factor in a decision. 490 U.S. 228 (1989).

In Comcast, the Court started with the fairly uncontroversial proposition that in tort law, a plaintiff must typically prove causation. The Court then noted that the typical causation standard is “but for” cause. After noting these basic points of law, the opinion waded onto more controversial ground. The Court assumed that a statute required a plaintiff to establish “but for” cause unless the statute either explicitly or implicitly provided otherwise. The Court found no such exception within the text or history of Section 1981.

The Court recognized that the text of Section 1981 does not explicitly contain causal language like the causal language typically used in tort law. The statute guarantees “all persons . . . the same right . . . to make and enforce contracts . . . as is enjoyed by white citizens.” The Court stated that this language was “suggestive” of a “but for” causation standard. The Court also indicated that the history of Section 1981 supported its holding.

The Court also looked to prior case law interpreting Section 1981 and noted that its interpretation of Section 1982 was relevant to Section 1981, citing Buchanan v. Warley, 245 U.S. 60 (1917). That case only discussed causation in a general sense and did not specify which causal standard should apply in Section 1982 cases. While Buchanan supports the idea that causation is an element of a Section 1982 claim, it does not stand for the more specific concept that the plaintiff is required to establish “but for” cause.

The Supreme Court also drew support for its holding from the 1991 amendments to Title VII and the lack of a similar amendment to Section 1981. In 1991, Congress amended Title VII in response to Price Waterhouse v. Hopkins, 490 U.S. 228, 240–41 (1989). In Price Waterhouse, the Supreme Court interpreted the causal language in Title VII to require the plaintiff to establish her protected trait was a “motivating factor” in an outcome. However, the Court allowed the employer to escape liability completely through an affirmative defense. If the employer established that it would have reached the same outcome without considering the plaintiff’s protected trait, the employer would prevail.

Congress believed that this affirmative defense was too employer-friendly. In 1991, Congress amended Title VII to make it more worker-friendly than Price Waterhouse. Congress explicitly included the motivating factor language within Title VII, but changed the affirmative defense from a complete defense to one that limited damages. 42 U.S.C. § 2000e-2(m); 42 U.S.C. § 2000e-5(g)(2)(B).

When Congress amended Title VII in 1991, it did not amend Section 1981 in a similar way. In Gross, the Court used Congress’s failure to amend the ADEA with similar provisions in 1991 to support the idea that Congress intentionally rejected the motivating factor standard for the ADEA. The Court used a similar argument in the Nassar case with respect to Title VII’s retaliation provision. In Comcast, the Court reiterated this same argument with respect to Section 1981.

During Comcast, the respondents argued that the causal standard might be different depending on the procedural posture of the case. The Supreme Court held that the required causal standard remains the same, even at different procedural stages. In other words, a plaintiff at the motion to dismiss stage must allege facts plausibly suggesting that the plaintiff can establish a protected trait was a “but for” cause of the challenged outcome. The Court noted that the kinds of materials that litigants would use to support or undermine causation might vary according to the procedural posture of the case. It is also worth noting that the procedural posture of the case also dictates how a court must view the evidence submitted by each party.

Unanimous Opinion Is a Surprise

The most surprising aspect of Comcast is the fact that it is unanimous. Justices Ginsburg, Sotomayor, Breyer, and Kagan joined the opinion, even though all four of these justices dissented in Nassar in 2013. Justices Ginsburg and Breyer dissented in Gross in 2009. Justices Kagan and Sotomayor joined the Court after Gross was argued. In Gross and Nassar, these justices heavily contested the idea that the words “because of” require a plaintiff to establish “but for” cause. In a concurring opinion in Comcast, Justice Ginsburg simply indicated in a footnote that while “but for” cause was “ill-suited to discrimination cases,” she believed the Court’s precedents required her to apply “but for” cause in this case.

Comcast and Bostock

The Supreme Court’s opinion in Bostock v. Clayton County, Ga., 140 S. Ct. 1731 (2020), may lessen some of the problems that might have followed Comcast. In Bostock, the Court held that Title VII prohibits discrimination because of sexual orientation and gender identity. Its reasoning centered on the ideas of causation: When an employer discriminates because of sexual orientation or gender identity, it is also discriminating “because of” sex. In his causation analysis, Justice Gorsuch emphasized a few key points about “but for” cause. He noted that “but for” cause can be sweeping and also emphasized:

  • “But for” cause does not mean sole cause.
  • Events can have multiple “but for” causes.
  • A protected trait does not need to be the primary reason to be the “but for” reason.

One reason plaintiffs’ attorneys had vigorously opposed “but for” cause is that many trial and appellate courts equated “but for” cause with sole cause and held that an outcome could only have one “but for” cause. Bostock puts many of these concerns to rest.

Bostock explains “but for” cause and thus provides guidance on how courts should resolve Section 1981 claims that involve multiple causes. Take the following example: A plaintiff claims her employer fired her because of her race and presents evidence to support her claim. The employer claims it fired her because she was late for work three times. At least three possible causal paths emerge from these facts: (1) the employer acted because of race; (2) the employer acted because of the employee’s tardiness; or (3) the employer acted because of some combination of the employee’s race and the fact that she was late. In most cases, it will be difficult to declare (at the motion to dismiss or summary judgment stage) that a plaintiff will be unable to establish “but for” cause.

In federal court, Fed. R. Civ. P. 12(b)(6) provides the standard for motions to dismiss based on failure to state a claim, and Fed. R. Civ. P. 56 provides the standard for summary judgment motions. In discrimination cases, the defendant is typically the party moving for summary judgment or to dismiss the case. The procedural rules for these motions require federal courts to view all evidence and inferences to be drawn from the evidence in favor of the non-moving party. The non-moving party is typically the plaintiff.

Given these procedural standards, it will often be inappropriate for a court to dismiss a case or grant summary judgment for the defendant based on the new causal standard. If a plaintiff has evidence that a protected trait played a role in an outcome, it will often be impossible to determine exactly what role the protected trait played at the motion to dismiss and summary judgment stages. As Bostock indicated, a party can establish “but for” cause when multiple causes exist.

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Sandra Sperino

Judge Joseph P. Kinneary Professor of Law, University of Cincinnati College of Law

Sandra Sperino is the Judge Joseph P. Kinneary Professor of Law at the University of Cincinnati College of Law, where she teaches and writes in the areas of employment discrimination, torts, and civil procedure. She is the author of McDonnell Douglas: The Most Important Case in Discrimination Law (Bloomberg).