Crowds are typically connected by a shared goal, ideology, objective or event. This includes but is not limited to people gathered at crime scenes, sporting events, concerts, celebrations, and planned demonstrations. Crowds encountered by police can range from less than a dozen to thousands of people.

Under the 1st Amendment, people have a right to free speech and assembly. This includes public demonstrations, protests, and marches. Because unrest or civil disorder can occur quickly with any size crowd, police are responsible for maintaining public order. Understanding the dynamics of crowd behavior allows police to act before it becomes a public safety hazard.