At common law, battery is the tort of intentionally (or, in Australia, negligently) and voluntarily bringing about an unconsented harmful or offensive contact with a person or to something closely associated with them (e.g. a hat, a purse). It is a form of trespass to the person. Unlike assault, battery requires an actual contact. The contact can be directly between the tortfeasor and the victim, or the tortfeasor may bring about the contact between an object and the victim. For example, A intentionally runs over B with his car. This is a battery. Battery is actionable per se, meaning that a claim for the tort may succeed without proof of damage.
Intent: The degree and quality of intent distinguishes tortious battery from criminal battery. The degree and quality of intent sufficient for battery also varies across different common law countries, and often within differing jurisdictions of those countries. In Australia, negligence in acting is sufficient to establish intent. Within the US, an intent to do the act that ultimately results in contact is sufficient for the tort of battery, while a intent to inflict an injury on another is required for criminal battery.
In the United States, the common law requires the contact for battery be "harmful or offensive". The offensiveness is measured against a 'reasonable person' standard. Looking at a contact objectively, as a reasonable person would see it, would this contact be offensive? Thus, a hypersenstive person would fail on a battery action if jostled by fellow passengers on a subway, as this contact is expected in normal society and a reasonable person would not find it offensive. Harmful is defined by any physical damage to the body.
Battery need not require body-to-body contact. Any volitional movement, such as throwing an object toward another, can constitute battery. Touching an object "intimately connected" to a person (such as an object he or she is holding) can also be battery. Intent can be transferred with battery, i.e. a person swings to hit one person and misses and hits another. He or she is still liable for a battery.
The standard defenses to trespass to the person, namely necessity and consent, apply to battery. As practical examples, under the first, a physician may touch a person without that person's consent in order to render medical aid to him or her in an emergency. Under the second, a person who has, either expressly or impliedly, consented to participation in a contact sport cannot claim in battery against other participants for a contact permitted by the rules of that sport.