Homicide is a manner of death, when one person causes the death of another. Not all homicide is murder, as some deaths caused by another person are manslaughter, and some are lawful; such as when justified by an affirmative defense, like insanity or self-defense.
Murder is when a person is accused of intentionally killing another person after planning to do so. There are no degrees of murder at common law. This is a modern statutory rule which divides murder into degrees according to its mens rea, but the exact definition of the degrees of murder varies by jurisdiction. Both first-degree murder and second-degree murder are intentional homicide crimes.
Manslaughter is when a person kills another person, but with less culpability. There may not have been intent, but the death occurred because of their actions. This can happen in accidental circumstances and sentences vary, but are usually less severe than second-degree murder.
Justifiable homicide may be when a person kills in self-defense or similar circumstances. It is not a legal charge but a classification used by police in cases where no crime was committed. The person who committed the killing will not be held criminally responsible, but civil penalties may still apply.
Felony murder is a type of homicide in which a person dies while the defendant is in the commission of a violent felony, even if they did not cause the death. Laws regarding homicide vary from state to state and can evolve and change over time.
[Last updated in January of 2023 by the Wex Definitions Team]