A failure to act. It is not usually a crime to fail to act; for example, it is not usually a crime to stand by and watch a child who has fallen into a river drown. Sometimes, however, there is a duty on a person to act, either because of the terms of a contractual duty, or because he is a parent or guardian of a minor, or because he has voluntarily assumed a duty (e.g. looking after a disabled relative), or through a statutory imposition of such a duty. In such cases, omission may constitute a crime. Usually this will be a crime of negligence (e.g. manslaughter, if the victim dies because of the defendant's omission); if it is a deliberate omission with a particular intention (e.g. the intention of starving someone to death) it will amount to murder. See also neglect.
Similarly, there is no general liability in the law of tort for failing to act, but there are some situations where the law imposes a duty to take action to prevent harm to others. Thus occupiers of premises are under a duty to see that their visitors are reasonably safe (see occupier's liability).