Criminal Investigators and Detectives in Policing

Written by Victor E. Kappeler, Ph.D.

People frequently associate criminal investigations with detectives. These perceptions are probably based on the many popular television shows and novels that characterize the detective as the person responsible for investigating crimes and bringing criminals to justice. Investigations are not the exclusive domain of detectives. Other police personnel such as those assigned to patrol, traffic, or other units in the department perform investigations. Patrol officers investigate criminal cases in their capacity as the first officer on the scene, and they generally complete preliminary investigations in criminal cases. Traffic officers investigate traffic accidents and situations or conditions that cause accidents. Records clerks, dispatchers, crime analysts, and other support personnel are involved in investigations by sorting through records and providing information to detectives and other officers. Investigation is a function performed by all police officers.

The term “detective” was first used in the 1840s. The London police created a detective unit in 1842, and in the 1880s a Special Irish Branch was created to control for agitation for a separate Ireland. Henry Fielding's Bow Street Runners of the 1750s concentrated on investigative activities rather than patrolling. Up until the 1920s, police detectives themselves were unsavory characters and quite often were immersed in crime or corruption. Unlike today, these early detectives focused on criminals instead of crimes. They seldom investigated a crime unless there was public pressure or the possibility of personal gain; instead, they focused on individual criminals.

The methods and techniques used by detectives evolved with changes in police administration. Around the turn of the century, sporadic efforts were made to eliminate police corruption and make the police accountable to the public. As the movement flourished, it brought changes in investigations. Police administrators elevated their expectations of detectives in terms of making arrests and clearing cases. The police “third degree” was born out of these new expectations. When faced with public, political, and departmental expectations for more arrests, detectives simply adopted methods that could produce these arrests. Police brutality and abuse of suspects became a way of life for detectives.

Two primary forces changed the nature of police investigations in the decades after World War II. First, efforts to professionalize the police escalated and put pressure on detectives to be even more accountable. Detectives began to focus on specific crimes and to respond to individual crime victims rather than only investigating criminals.  Second, the due process revolution of the 1960s placed new legal constraints on police investigations. The U.S. Supreme Court handed down a number of cases that restricted how police officers performed investigations.

Today, nationally between 10 to 15% of a department's sworn personnel are assigned to a detective unit. In larger departments, investigations are the responsibility of detectives who are assigned full-time to this role. In smaller agencies, patrol officers are responsible for conducting investigations due to the limited number of employees and workload of the department. Some departments divide responsibility for investigations between patrol and detective units whereby patrols investigate minor offenses or, in some cases, the majority of all offenses. Generally, small municipal or county departments will have a state agency investigate crimes, as they do not have the personnel or training to conduct sophisticated investigations. The percentage of departments investigating arson is lower because, in many jurisdictions, fire departments conduct arson investigations. The percentage of departments investigating environmental crimes is low because those crimes often are investigated by a state or federal agency.

The investigative workload in our nation's largest cities requires specialization within the detective unit. The most common detective specializations are “crimes against property” units and “crimes against persons” units. Even more specialization frequently occurs within these two broadly defined units; for example, common units found in crimes against persons divisions include homicide, sex crimes, domestic violence, and crimes against children. Burglary, robbery, and auto theft are common crimes against property units.

Victor E. Kappeler, Ph.D.
Associate Dean and Foundation Professor
School of Justice Studies


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Published on October 15, 2012