Can a jury have properly determined that personal use of a knife was an element of the crime of murder?

Neither could any juror have properly so determined. The due process clause of the Fourteenth Amendment "protects the accused against conviction except upon proof beyond a reasonable doubt of every fact necessary to constitute the crime with which he is charged." (In re Winship (1970) 397 U.S. 358, 364, 90 S.Ct. 1068, 1073, 25 L.Ed.2d 368.) That means not only every "elemen[t]" properly so called, but also every "fac[t] necessary to establish each of those elements...." (Sullivan v. Louisiana (1993) 508 U.S. 275, ----, 113 S.Ct. 2078, 2080, 124 L.Ed.2d 182.) It is true that personal use of a knife is not an element of the crime of murder. It is also true that, generally, it is not even a necessary fact for any of the elements. But it is indeed such a fact for the requisite unlawful act insofar as guilt is predicated on a theory dependent thereon --in this case, on a theory that defendant was a principal as a direct and active perpetrator solely through his personal use of a knife. Similarly, intent to steal is not an element of the crime of murder. Neither, generally, is it a necessary fact for any of the elements. But it is indeed such a fact for the requisite unlawful mental state insofar as guilt is predicated on a theory dependent thereon, for example, felony-murder robbery. Obviously, no juror can determine that a defendant is guilty of a crime beyond a reasonable doubt on a theory dependent on a necessary fact as to which each and every juror has a reasonable doubt.

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