What is Homicide?

Legal Definition
Homicide refers to one human being killing another. Homicides can be divided into many overlapping types, including murder, manslaughter, justifiable homicide, killing in war, euthanasia, and capital punishment, depending on the circumstances of the death. These different types of homicides are often treated very differently in human societies; some are considered crimes, while others are permitted or even ordered by the legal system.
-- Wikipedia
Legal Definition
Homicide is when one human being causes the death of another. Not all homicide is murder, as some killings are manslaughter, and some are lawful, such as when justified by an affirmative defense, like insanity or self-defense.
Legal Definition
Crim. law. According to Blackstone, it is the killing of any human creature. 4 Com. 177. This is the most extensive sense of this word, in which the intention is not considered. But in a more limited sense, it is always understood that the killing is by human agency, and Hawkins defines it to be the killing of a man by a man. 1 Hawk. c. 8, s. 2. See Dalloz, Dict. h. t. Homicide may perhaps be described to be the destruction of the life of one human being, either by himself, or by the act, procurement, or culpable omission of another. When the death has been intentionally caused by the deceased himself, the offender is called felo de se; when it is caused by another, it is justifiable, excusable, or felonious.

2. The person killed must have been born; the killing before birth is balled foeticide. (q. v.)

3. The destruction of human life at any period after birth, is homicide, however near it may be to extinction, from any other cause.

4. - 1. Justifiable homicide is such as arises, 1st. From unavoidable necessity, without any will, intention or desire, and without any inadvertence in the party killing, and therefore without blame; as, for instance, the execution, according to law, of a criminal who has been lawully sentenced to be hanged; or, 2d. It is committed for the advancement of public justice; as if an officer, in the lawful execution of his office, either in a civil or criminal case, should kill a person who assaults and resists him. 4 Bl. Com. 178-1 80. See Justifiable Homicide.

5. - 2. Excusable homicide is of two kinds 1st. Homicide per infortunium. (q. v.) or, 2d. Se defendendo, or self defence. (q. v.) 4 Bl. Com. 182, 3.

6. - 3. Felonious homicide, which includes, 1. Self-murder, or suicide;2. Man-slaughter, (q. v.); and , 3. Murder. (q. v.) Vide, generally, 3 Inst. 47 to 57; 1 Hale P. C. 411 to 602; 1 Hawk. c. 8; Fost. 255 to 837; 1 East, P. C. 214 to 391; Com. Dig. Justices, L. M.; Bac. Ab. Murder and Homicide; Burn's Just. h. t.; Williams' Just. h. t.; 2 Chit. Cr. Law, ch.9; Cro. C. C. 285 to 300; 4 Bl. Com. to 204; 1 Russ. Cr. 421 to 553; 2 Swift's Dig. 267 to 292.
-- Bouviers Law Dictionary
Legal Definition
The killing of any human creature, 4 Bl. Comm. 177. The killing of one human being by the act, procurement or omission of another. Pen. Code N. Y. ยง 179. The act of a human being in taking away the life of another human being. Sanders v. State, 113 Ga. 267, 38 S. E. 842; People v. Hill, 49 Hun. 432, 3 N. Y. Supp. 564; Maher v. People, 10 Mich. 212, 81 Am. Dee, 781; State v. Lodge, 9 Houst (Del.) 542, 33 Atl. 312; Com. v. Webster, 5 Cush. (Mass.) 303, 52 Am. Dec. 711. Homicide is not necessarily a crime. It is a necessary ingredient of the crimes of murder and manslaughter, but there are other cases in which homicide may be committed without criminal intent and without criminal consequences, as, where it is done in the lawful execution of a judicial sentence, in self-defense, or as the only possible means of arresting an escaping felon. The term "homicide" is neutral; while it describes the act, it pronounces no judgment on its moral or legal quality. See People v. Connors, 13 Misc. Rep. 582, 35 N. Y. Supp. 475. Classification. Homicide is ordinarily classified as "justifiable," "excusable," and "felonious." For the definition of these terms, and of some other compound terms, see infra.
See also
-- Black's Law Dictionary
Legal Definition
A killing of one person by another. See 10 Mich. 212, 81 Am. Dec. 781.
-- Ballentine's Law Dictionary