Reasonable creature
Black's Law Dictionary · Henry Campbell Black, M.A. · 1910
Black's Law Dictionary
Under the common-law rule that murder is taking the life of a "reasonable creature" under the king's peace, with malice aforethought, the phrase means a human being, and has no reference to his mental condition, as it includes a lunatic, an idiot, and even an unborn child.
See State v. Jones, Walk. (Miss.) 85.