Русско-англо-русский юридический словарь

Murder is always intentional and the kind of intention which is required by the law is called malice aforethought in legalese. (TransLegal)

Involuntary manslaughter is the unlawful killing of a human being without malice aforethought, either expressed or implied. It is distinguished from voluntary manslaughter by the absence of intention. (Wikipedia)

At common law, murder was defined as killing with malice aforethought. (Legal Information Institute)