Police accountability involves holding both individual police officers and law enforcement agencies responsible for effectively delivering basic crime control services and maintaining order, while treating individuals fairly and within the bounds of the law. Police are expected to uphold laws, regarding due process, search and seizure, arrests, discrimination, as well as other laws relating to equal employment, sexual harassment, etc. Holding police accountable is important for maintaining the public's "faith in the system". Research has shown that the public prefers independent review of complaints against law enforcement, rather than relying on police departments to conduct internal investigations. Public perception of police accountability can be partisan. Electoral accountability can improve police accountability of asset forfeiture.

The police professionalism approach introduced by August Vollmer and advocated by O.W. Wilson largely ignored issues of police accountability and how officers should handle situations involving discretion. In order to prevent the misuse of discretion, it is necessary to establish a Code of Ethics to serve as a guideline. It is impossible to foresee a provision for every possible scenario; instead codes of ethics are used to provide officers a tool that is flexible, open for interpretation and can be applied in various manners depending on the situation at hand.

Use of force by police may involve firearms, as well as other means. Prior to the 1970s, there were generally no written policies or review procedures regarding use of force by law enforcement in the United States. In 1972, New York City Police Department Commissioner Patrick V. Murphy instituted a new policy that confined discretion in use of force to situations only where the officer's own life, or that of other people are in danger. This defense of life rule replaced the fleeing felon rule. The 1985 Supreme Court decision, Tennessee v. Garner ruled that police may only use deadly force to prevent escape when the officer has probable cause to believe that the suspect poses a significant threat of death or serious physical injury to the officer or others.

Since the NYPD instituted new policies on use of force, many other law enforcement agencies have followed suit, establishing a written policy that set guidelines as to when use of force is appropriate. Procedures may include requiring officers to file written reports following each incident. For incidents involving firearms or other use of deadly force, an internal investigation and review is often required. A mechanism in place for administrative review of other use of force incidents may also be part of the policy.

Not all law enforcement agencies in the United States had instituted reforms in the 1980s and 1990s. The United States Department of Justice investigated patterns of abuse within the Pittsburgh Bureau of Police, among other agencies, and brought legal action to force changes.

Less-than-lethal weapons, such as chemical sprays, are used as alternatives to deadly force. These weapons also require policies on their use, along with training on proper use. Police officers are also encouraged to consider a use of force continuum, and try to deescalate situations with verbal warnings and persuasion.

Studies have shown that police officers that wear body cameras while on duty have fewer instances of misconduct and excessive force. In addition, it appears their usage is responsible for a decline in complaints against officers. In order for the usage of body-cameras to be effective, it is important that police officers ensure they are functioning correctly. The devices are not immune to malfunctioning, which could cause critical gaps in recordings. In addition, they can easily be manipulated to face a different direction, or the view can easily be obstructed by other means. According some studies, body cameras fail to capture more than half of incidents in which officers used force.

Some are worried about the privacy of victims who may be recorded by police officers wearing body cameras, raising concerns regarding possible retaliation against those captured cooperating with law enforcement.