Perhaps this will help you:
Use of Force
Every day, law enforcement officers face danger while carrying out their responsibilities. When dealing with a dangerous—or unpredictable—situation, police officers usually have very little time to assess it and determine the proper response. Here, good training can enable the officer to react properly to the threat or possible threat and respond with the appropriate tactics to address the situation, possibly including some level of force, if necessary, given the circumstances.
The U.S. Commission on Civil Rights has stated that "…in diffusing situations, apprehending alleged criminals, and protecting themselves and others, officers are legally entitled to use appropriate means, including force." In dozens of studies of police use of force there is no single, accepted definition among the researchers, analysts, or the police. The International Association of Chiefs of Police (IACP) in its study, Police Use of Force in America 2001, defined use of force as "The amount of effort required by police to compel compliance by an unwilling subject." The IACP also identified five components of force: physical, chemical, electronic, impact, and firearm. To some people, though, the mere presence of a police officer can be intimidating and seen as use of force.
The Bureau of Justice Statistics (BJS) in Data Collection on Police Use of Force, states that "…the legal test of excessive force…is whether the police officer reasonably believed that such force was necessary to accomplish a legitimate police purpose…" However, there are no universally accepted definitions of "reasonable" and "necessary" because the terms are subjective. A court in one jurisdiction may define "reasonable" or "necessary" differently than a court in a second jurisdiction. More to the point is an understanding of the "improper" use of force, which can be divided into two categories: "unnecessary" and "excessive." The unnecessary use of force would be the application of force where there is no justification for its use, while an excessive use of force would be the application of more force than required where use of force is necessary.
Contacts between Police and the Public, a 1999 BJS report, estimated that less than half of 1 percent of an estimated 44 million people who had face-to-face contact with a police officer were threatened with or actually experienced force. Other studies report similar statistics. It is these few situations, however, that attract public attention. Robert K. Olsen, former Minneapolis Police Chief and Past President, Police Executive Research Forum (PERF), early in 2004 called the use of force "the single most volatile issue facing police departments." He noted that "just one use of force incident can dramatically alter the stability of a police department and its relationship with a community."
Police department policies can have a significant impact on how force is used in street-level encounters, says a 2003 study by the Community Relations Services of the U.S. Department of Justice, Principles of Good Policing: Avoiding Violence Between Police and Citizens. And, the BJS Data Collection report mentioned above stresses the need for police executives to improve training of recruits and police officers on the use of force and the techniques for minimizing its application.