In two Supreme Court cases, the court established employers are subject to liability for unlawful harassment by supervisors resulting in a tangible employment action, such as a firing, a demotion or assigning undesirable work. Since then, thousands of unlawful harassment suits have been filed against employers.
The lawsuits established if harassment by a supervisor results in a tangible employment action, you cannot present any defenses. However, if harassment by a supervisor does not result in a tangible employment action, you can present a defense.
A defense to such a claim consists of two necessary elements: you exercising reasonable care to prevent or promptly correct any harassment and the harassed employee unreasonably failing to avoid harm and take advantage of any preventive or corrective opportunities you have provided.
You probably are aware you must establish, publicize and enforce anti-harassment and anti-discrimination policies and complaint procedures to have any hope of meeting the first element of the defense. But though you may be aware of the need to have such policies, effective implementation is critical to a defense.