The short answer to this question is a resounding yes, as illustrated by a recent decision from the Ninth Circuit Court of Appeals.
In Mayo v. PCC Structurals, Inc., the Ninth Circuit Court of Appeals rejected claims for disability discrimination brought by an employee who made threats of violence in the workplace. Specifically, the employee stated that he felt “like coming down with a shotgun and blowing off” the heads of a supervisor and a manager. He told another employee that he planned to “take out management,” and also said that he wanted “to bring a gun down and start shooting people.” After these threats were reported, the employer wisely terminated the employee. The employee responded not with a shotgun, but with a lawsuit, in which he claimed that his employer discriminated against him based on his being disabled with a major depressive disorder.
In rejecting the claim, the court stated that “an essential function of almost every job is the ability to appropriately handle stress and interact with others. And while an employee can be qualified despite adverse reactions to stress, he is not qualified when that stress leads him to threaten to kill his co-workers in chilling detail and on multiple occasions (here, at least five times). This vastly disproportionate reaction demonstrated that Mayo could not perform an “essential function” of his job, and was not a “qualified individual.” This is true regardless of whether Mayo’s threats stemmed from his major depressive disorder.”
This decision makes it clear that employers do not need to tolerate threats of violence in the workplace, regardless of whether they stem from a mental disability. Federal and state anti-discrimination laws do not require employers to play dice with the lives of their workforce.