The crime of assault varies from state to state (and under federal law), but is generally defined as intentionally putting another person in reasonable apprehension or fear of an imminent (immediate) harmful or offensive contact. The crime of assault may be committed even if there is no physical contact, as the criminal physical contact constitutes the separate crime of battery. In many states assaulting a police officer or peace officer who is performing official duties (such as making a lawful arrest) is a more serious offense—sometimes a felony.

In Pennsylvania, assault is categorized into two main types: simple assault and aggravated assault. Simple assault is generally defined as attempting to cause or intentionally, knowingly, or recklessly causing bodily injury to another; negligently causing bodily injury with a deadly weapon; or attempting by physical menace to put another in fear of imminent serious bodily injury. Simple assault is usually a misdemeanor. Aggravated assault, a more serious offense, involves causing or attempting to cause serious bodily injury to another, or causing injury to someone while showing extreme indifference to human life. Aggravated assault can be a felony and is more serious when committed against certain protected classes, including police officers and other peace officers performing their duties. Assaulting a police officer in Pennsylvania is indeed considered a more serious crime and can lead to felony charges, reflecting the state's interest in protecting law enforcement personnel while they perform their official duties.