In common law, assault is the tort of acting intentionally, that is with either general or specific intent, causing the reasonable apprehension of an immediate harmful or offensive contact. Assault requires intent, it is considered an intentional tort, as opposed to a tort of negligence. Actual ability to carry out the apprehended contact is not necessary. 'The conduct forbidden by this tort is an act that threatens violence.'
In criminal law an assault is defined as an attempt to commit battery, requiring the specific intent to cause physical injury.
Comparison to battery
As distinguished from battery, assault does not need to involve the 'unwanted physical contact; but is the anticipation of such contact'. It only needs intent to make or threaten contact and the resulting apprehension. At one point, the common law understanding of assault required more than words alone, it also required an overt act. This understanding has changed, while words alone cannot be construed as assault, words coinciding with actions or circumstances that would put a person in reasonable apprehension that a harm or offensive contact was likely to occur would. For example, an actor shouting "I'm going to kill you" while not moving but in complete shadow and with a knife in their hand could be interpreted as assault.
Additionally, fear is not required for an assault to occur, only anticipation of subsequent battery. A battery can occur without a preceding assault, such as if a person is struck in the back of the head. An assault can be an attempted battery.
I.e. 'If Henry points a gun at Thomas he has committed an assault. It makes no difference whether the gun is loaded,' But 'Henry will only commit a battery if he shoots the gun and hits Thomas'.
Elements
Defined by Collins v Wilcock as 'an act which causes another person to apprehend the infliction of immediate unlawful force on his person', 'assault protects the claimant who fears or apprehends a battery.' Three elements must be established in order to establish tortious assault: first, there must be a positive act by the defendant; second, the plaintiff had reasonable apprehension (the requisite state of mind) of immediate physical contact, and third, the defendant's act of interference was intentional (the defendant intended the resulting apprehension).
An actionable assault requires that:
'the defendant intends that the claimant apprehends the application of unlawful force; the claimant reasonably apprehends the immediate and direct application of unlawful force; for which the defendant has no lawful justification or excuse.'
But intent for purposes of civil assault can be either general or specific. Specific intent means that when the defendant acted, he or she intended to cause apprehension of a harmful or unwanted contact. General intent means that the defendant knew with substantial certainty that the action would put someone in apprehension of a harmful or unwanted contact.
While the law varies by jurisdiction, contact is often defined as harmful if it objectively intends to injure, disfigure, impair, or cause pain. The act is deemed offensive if it would offend a reasonable person's sense of personal dignity. While imminence is judged objectively and varies widely on the facts, it generally suggests there is little to no opportunity for intervening acts. Lastly, the state of apprehension should be differentiated from the general state of fear, as apprehension requires only that the person be aware of the imminence of the harmful or offensive act.
It is clear that 'all forms of trespass require an intentional act. An act of negligence will not suffice.' There must be capacity and immediacy - simply threatening someone will not suffice.
Whilst it has been speculated that words alone do not constitute assault, there must be an act (I.e. in R v Meade), this was questioned in R v Ireland it was held that repeated silent telephone calls being made can constitute an assault:
'The proposition that a gesture may amount to an assault, but that words can never suffice, is unrealistic and indefensible.''' - Lord Steyn
Moreover, In Australia, the test for proving tortious assault is formulated as requiring 'proof of an intention to create in another person an apprehension of imminent harmful or offensive contact' .