homicide, the killing of one human being by another. Homicide is a general term and may refer to a noncriminal act as well as the criminal act of murder. Some homicides are considered justifiable, such as the killing of a person to prevent the commission of a serious felony or to aid a representative of the law. Other homicides are said to be excusable, as when a person kills in self-defense. A criminal homicide is one that is not regarded by the applicable criminal code as justifiable or excusable. All legal systems make important distinctions between different types of homicide,