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D'andra Millsap Shu, The Coming Causation Revolution in Employment Discrimination Litigation, __ Cardozo L. Rev. __ (forthcoming 2022), available at SSRN.

Two simple words, “because of,” are at the heart of most anti-discrimination statutes, which preclude employers from taking adverse action because of a protected characteristic. Two simple words. Yet, the myriad attempts by courts and commentators to make sense of these two simple words has appropriately been referred to as a “morass,” a “jungle,” and a “quagmire.”

There have been two battlegrounds. First is the question of which causal standard applies. Does the phrase refer to “but for” causation? “Motivating factor” causation? “Primary” or “predominate” causation? “Substantial factor” causation? “Sole” causation? Some combination of these? Or something else? Second–and the focus of Professor Shu’s article, The Coming Causation Revolution in Employment Discrimination Litigation–is that even when courts seem to agree on a standard, such as “but for,” they seem unable to agree on what that standard means. Now that the Court appears to have coalesced around the idea that “because of” generally refers to “but for” causation (even if some scholars might still argue for other standards), Professor Shu convincingly argues that the second battleground – over the meaning of “but for” – is the most important one.

My first question, as a scholar of causation, might be: How can people disagree over the meaning of “but for”? This concept, also known as “necessity,” has been with us since the time of the ancient Greek philosophers. It asks whether, if you remove Factor X, the event in question would still have occurred. If the answer is no, then Factor X is a “but for” cause of the event (or “necessary” to the occurrence of the event).

But never underestimate the ability of employment lawyers, professors, and courts to mess things up.  And Professor Shu makes the case that our crowd managed to create uncertainty over the meaning of “but for,” with some pretty serious consequences.

The confusion has to do with a third word that the Gross court added to the phrase “because of.” Gross may be best known for equating “because of” with “but for” causation. But instead of saying that the ADEA required plaintiffs to prove that age was a “but for” cause of the adverse employment action, the Court said that plaintiffs need to show that age was the “but for” cause of that action. This may have been a mistake, or it may have been a backhanded attempt by the Court to invent a narrower version of “but for.” But as Professor Shu points out, the Court’s addition of the word “the” to “but for cause” added to the confusion in the causation arena, prompting several courts to assume (incorrectly) that there can be only one “but for” cause, and therefore effectively applying a “sole cause” standard in anti-discrimination cases. (“Sole cause” is much more restrictive than “but for.”)

This back-door “sole cause” test wrought havoc on cases with multiple causes – including those in which plaintiffs plead alternative theories (such as race or retaliation), those in which plaintiffs allege intersecting causes (such as age and sex), and even McDonnell-Douglas pretext cases in which the defendant was able to offer a single unrebutted legitimate reason for the adverse employment action.

Professor Shu makes the optimistic argument that the Supreme Court has now fixed this problem in Bostock. Though Bostock is known as the case that held that sex discrimination includes discrimination on the basis of sexual orientation and gender identity, Professor Shu focuses on its “but for” reasoning: that sex is a “but for” factor in sexual orientation or gender identity discrimination. In reaching that conclusion, Justice Gorsuch provided a mini-class on “but for” causation, emphasizing (correctly) that there can be – and often are – multiple “but for” causes of a decision. Not only does he debunk the idea that there can be only one “but for” cause, he makes painfully clear that the statute (Title VII, in that case) does not require “sole causation,” and that “but for” is the exclusive standard. For example, he makes clear that there is no “primary” or “predominant” cause requirement.

Professor Shu argues that Justice Gorsuch’s lesson in causation is completely clear and, perhaps more importantly, that it applies to any statute for which the Court has adopted its default “but for” standard.  In other words, in any employment case involving “but for” causation, courts should now have a roadmap that lets them avoid the pitfalls of “sole cause,” “primary cause,” or any other distraction. I love her optimism, and I hope she is right (though she notes that at least one court–the 6th Cir.–has continued to hold to the Gross-induced idea that “but for” somehow means “sole cause.”)

The article is unabashedly doctrinal, though with a good understanding of and integration of the normative literature in the field. It identifies an important but underappreciated problem caused by an unheralded part of Gross, and a solution grounded in an unheralded part of Bostock.

Some of the many reasons to read Professor Shu’s new article include:

  • A laser-like focus on “but for” causation. Many scholars have argued, based on normative and/or doctrinal reasons, that “but for” should be replaced by another standard, such as “motivating factor.” But Professor Shu argues persuasively that this boat has sailed; the Court has chosen “but for.” So we would do best to focus on making sure that the courts get “but for” right. She also includes a nice summary and interpretation of some empirical work suggesting that when judges and juries fully understand “but for” – and distinguish it from “sole cause” – they can and do find for plaintiffs in appropriate cases.
  • An excellent typology and explanation of the stakes when the courts get “but for” wrong. Perhaps most important in her list is the concept of intersectionality, which, though well theorized, can quickly become a victim of bad causal reasoning. Additionally, she explains how bad causal reasoning can quickly derail McDonnell-Douglas pretext cases, erroneously allowing defendants to win if they advance a single unrebutted reason for their actions.
  • A good explanation of how courts have been confused by – or perhaps simply resistant to – Justice Gorsuch’s attempt to clarify “but for” in Bostock, along with a good argument for why this clarification should apply in “but for” cases under all statutes; that it makes little sense to think of Bostock’s “but for” lesson as being limited to Title VII.

Perhaps what I like best about Professor Shu’s article is its reflection of her optimism. She believes that a clear, cogent explanation of “but for” by one of the top jurists in the country not only should, but just might, clear up the confusion in this area. Optimism is good. (Said the optimist.)

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Cite as: Martin J. Katz, Has the Meaning of “Because of” Finally been Solved?, JOTWELL (July 18, 2022) (reviewing D'andra Millsap Shu, The Coming Causation Revolution in Employment Discrimination Litigation, __ Cardozo L. Rev. __ (forthcoming 2022), available at SSRN),