Police departments are modeled after military organizations in terms of their training and rank structure. Police officers share the bond of attending a police academy, wear uniforms and are required to obey the orders of those of higher rank. With a few variations, nearly all metropolitan police departments use similar ranks. The top rank is usually police commissioner and/or chief, followed by captain, lieutenant, sergeant, detective and police officer.

Police Commissioner or Police Chief

The highest rank in most police departments is police commissioner or police chief. Some large cities, such as New York, have both a police commissioner and a police chief. The top police official is typically appointed by a civilian authority such as a city council or mayor. In large police forces, the job of a police commissioner often involves public policy as much as, if not more than, management of the police force. A police chief is usually more directly involved in departmental management in smaller police forces.

Police Captain

Unless there is an assistant police chief or commissioner, a police captain is the rank immediately below commissioner. Captains typically have at least 10 to 15 years of police experience, and are usually required to have at least a bachelor's degree. Police captains are often in charge of a division of the police force, such as the forgery, organized crime, community service or cyber-crime division. Promotion to captain requires a distinguished service record and a very high aptitude test score.

Police Lieutenant

Police lieutenants typically have at least six or seven years of service. A college degree is the minimum educational requirement in most cases. Police lieutenants are often in charge of a platoon of police officers, and one or more lieutenants is designated to fill in for a divisional captain in his absence. The job description of a lieutenant mainly comprises administrative and management duties, but the lieutenant on duty is expected to respond to scenes of serious crime scenes such as officer-involved shootings or homicides. Promotion to lieutenant requires excellent job reviews and high test scores.

Police Sergeant

Police sergeants usually have at least five years on the force. Educational requirements vary, but most departments require some college or an associate degree. Sergeants frequently serve as shift watch commanders or assistant watch commanders. This entails preparing daily patrol assignments, inspecting police personnel and equipment, supervising patrol officers, reviewing reports, investigating complaints and responding to crime scenes if requested. Promotion is based on positive job performance reviews and aptitude test scores.

Police Detective

Detectives are a special class of police officers who are responsible for investigating crimes. Detectives are typically expected to have some college. Most departments have two or three detective ranks, such as Detective I and Detective II. Some departments also have a detective-sergeant rank. Promotion to detective typically requires one year of service and a relatively high score on an aptitude test.

Police Officer

Most departments have three police officer ranks. Police Officer I is a probationary officer who automatically becomes a Police Officer II after 6 to 12 months. Promotion to Police Officer III might take another one to three years, based on job performance reviews. Many larger police departments require police officers to have some college, but a high school diploma is sufficient to serve as a police officer in most small towns and rural jurisdictions.