Law enforcement officers have a duty to intervene when they have an opportunity to prevent another officer from using unlawful force. That duty comes from multiple sources, including federal constitutional law, a new state statute, and, in some cases, agency policy. But what does the duty require in practice? Is verbal intervention enough, or must the officer attempt to intercede physically? What if the officer has competing obligations, such as keeping control of an unruly scene? And what should an officer do if he or she isn’t sure whether the amount of force another officer is using is appropriate? This post will address how officers and agencies might operationalize the duty to intervene.