Missouri seems poised to amend its state EEO law to require a plaintiff alleging employment discrimination to show that "the protected criterion was the motivating factor." I view this as but-for causation in disguise because the new law also would define "motivating factor" to mean that the protected criterion "had a determinative influence on the adverse decision or action." A but-for factor, a determinative factor, a factor that made a difference -- these are all the same thing. So superficially, it looks like Missouri is adopting a motivating-factor causation standard, but in reality, I see the state as adopting a but-for causation standard.
As I discuss in this prior post, Missouri currently applies a "contributing factor" causation standard, which is a lower standard of causation than motivating factor, meaning that it is easier for a plaintiff alleging discrimination to establish that his race, sex, age, or other protected criterion was a contributing factor than for him to show that it was a motivating factor, which, in turn, is easier for him to show than but-for causation. Contributing-factor causation is a subset of motivating-factor causation, and motivating-factor causation is a subset of but-for causation. Thus, if a plaintiff has established but-for causation, he has also necessarily established both motivating-factor and contributing-factor causation.
One benefit of adopting the but-for causation standard is that the concept of but-for causation is much better understood than the fuzzy concepts of motivating-factor and contributing-factor causation. But-for causation means that if the plaintiff had been of another protected group, then the alleged discrimination would not have occurred. For example, if a woman establishes that but for her sex she would not have been denied a promotion, then that means that if she had been a man and everything else had been the same, she would have gotten the promotion. By contrast, what it means for sex/race/etc. to have been a motivating factor is much harder to grasp. Does that mean it just needs to have been a factor in the decisionmaker's mind that weighed in favor of the ultimate outcome? Or must it have been a much more significant consideration? (For more on the causation standards, see this post.)
To be sure, but-for causation is harder to prove than contributing-factor causation, or even motivating-factor causation. But that is largely only a theoretical, and not a real-world, benefit if no one really knows what contributing-factor causation and motivating-factor causation even mean.
And when it comes to the real world, but-for causation rules the day. In Gross v. FBL Financial Services, the Supreme Court held that a plaintiff alleging a violation under the Age Discrimination in Employment Act must show that but for his age, he would not have been subjected to the adverse job action. Gross effectively adopted a default but-for causation standard for federal EEO law. Gross was widely criticized by employee rights advocates as making it more difficult for plaintiffs to prevail under the ADEA. But Gross has turned out to have had little effect because in the vast majority of EEO cases plaintiffs establish violations by relying on the McDonnell Douglas framework. Under this approach, a plaintiff establishes that an employer's asserted reason for taking a challenged job action was a pretext for discrimination. This method of proof is widely understood to establish but-for causation. In adopting a new causation standard, the Missouri legislature has also explicitly endorsed the McDonnell Douglas framework, so as with federal ADEA claims, it seems reasonable to expect that most Missouri plaintiffs will be unaffected by the change in Missouri law.
This blog reflects the views solely of its author. It is not intended, and should not be regarded, as legal advice on how to analyze any particular set of facts.