In the United States and elsewhere, legal systems commonly recognize that laws governing the treatment of the act of assault must recognize certain groups of people as being especially entitled to protection under the law. In some cases these privileges can be incurred by people unusually vulnerable to assault.
Other such protected groups can be found in those who are considered particularly important to a society's proper functioning. For this latter rationale, the act of assault on a police officer is typically punished particularly stringently, with higher penalties and fewer allowances made for mitigating factors as may be understood in other assault cases.
In the language of legal provisions setting apart the act of assault on a police officer from other crimes, law enforcement figures are commonly referred to as "peace officers" and included with other public service providers, such as firefighters and paramedics.
The allowance of a discretionary amount of force in making arrests accorded to police officers typically entails that the right to self-defense against such an application of force may be more limited than is typically the case for defendants in assault cases. A basic concept of assault and battery law, that of the enjoyment of some form of "privilege" to employ physical force, can be seen applying particularly strongly to the rights of police officers.
As in other areas of assault law, the main consideration to be made is that the use of force occurred within reasonable limits suited to the context of their occurrence. For instance, a defendant who was jaywalking would probably not merit being met with the same response as a defendant committing an armed robbery.
Even in the cases of an unreasonably made arrest, it must be demonstrated that the defendant accused of assault on a police officer felt an imminent danger of serious bodily harm and responded with an appropriate amount of force. For this reason, an assault on a police officer is likely to carry some form of penalty unless evidence strongly points against the conduct of the arrest which occasioned it.
In the United States, it is generally required before an assault on a police officer can be tried that it be demonstrated, firstly, that the victim was discharging such a duty at the time of the assault and, secondly, that the motivation for the assault was occasioned by the performance of such duties.
In regard to the definition accorded to the term "police officers," marshals for municipal courts, members of sheriff departments, and officers with highway services are defined as such and are, therefore, subject to the same protections and privileges.
Within the United Kingdom, an assault on a police officer is considered a form of aggravated assault, which is referred to as "assault on a constable in the execution of his duty," language intended to codify the principle that an assault on a police officer is only distinguished from other assaults if it occurs for that reason