The wrongful act by the defendant must be volitional. Generally, this requirement is easily met — it is merely a voluntary muscular movement (e.g., pulling the trigger on a BB gun), regardless of the defendant’s state of mind with respect to the consequences of the act.
On the other hand, an act is not volitional if it is not dictated by the defendant’s mind or is beyond the defendant’s mental control. For instance, it is not a battery to strike someone in the course of an epileptic seizure, or to knock over a fellow passenger on a bus because it suddenly lurches to a stop. Similarly, there is no volitional act and hence no trespass to land if people physically carry a defendant onto plaintiff’s property.
By contrast, there is a volitional act if defendant runs onto plaintiff’s property to escape a vicious dog. Defendant’s reasons for the act may give rise to an affirmative defense (e.g., private necessity), but are irrelevant to the volitional act requirement.