In Schad v. Arizona, 501 U.S. 624, (1991) the defendant claimed that the United States Constitution required juror unanimity in capital cases, id. at 630, the United States Supreme Court rejected Schad's argument that premeditated murder and felony murder in Arizona are separate crimes for which the jury must return separate verdicts. In its plurality opinion upholding the constitutionality of allowing a jury to return a general verdict, the Court noted that "legislatures frequently enumerate alternative means of committing a crime without intending to define separate elements or separate crimes." Id. at 636. Further, "it has long been the general rule that when a single crime can be committed in various ways, jurors need not agree upon the mode of commission." Id. at 649 (Scalia, J., concurring). The Supreme Court held that "there is no general requirement that the jury reach agreement on the preliminary factual issues which underlie the verdict." Id. at 632. The Court said: "We have never suggested that in returning general verdicts in such cases the jurors should be required to agree upon a single means of commission." Id. at 631. In addition, "it is . . . impossible to lay down any single analytical model for determining when two means are so disparate as to exemplify two inherently separate offenses." Id. at 643. The Supreme Court held that due process did not require the jury, in convicting the defendant of first degree murder, to agree on one of the alternative statutory theories of premeditated or felony murder. While a majority of the court agreed that due process imposes some limits on the degree to which different states of mind may be considered merely alternative means of committing a single offense, the court could not agree on the extent of those due process limitations or how they should be applied. ( Id. at pp. 632, 651, 656.) In delivering the plurality opinion of the court, Justice Souter explained that there can be no single test for determining when two means are so disparate as to exemplify two inherently separate offenses. ( Id. at pp. 633-637, 643.) Based on the principle that "States must be permitted a degree of flexibility in determining the 'facts necessary to constitute the crime' " ( id. at p. 638), Justice Souter concluded that "where a State's particular way of defining a crime has a long history, or is in widespread use, it is unlikely that a defendant will be able to demonstrate that the State has . . . defined as a single crime multiple offenses that are inherently separate" ( id. at p. 640). Finding, however, that history and widespread practice are not dispositive of the due process issue, Justice Souter then proceeded to address the level of culpability involved in the alternative mental states for first degree murder. ( Id. at pp. 642-644.) As Justice Souter explained, "Whether or not everyone would agree that the mental state that precipitates death in the course of robbery is the moral equivalent of premeditation, it is clear that such equivalence could reasonably be found, which is enough to rule out the argument that this moral disparity bars treating them as alternative means to satisfy the mental element of a single offense." ( Id. at p. 644.) Thus, the court held that federal due process did not require the jury to unanimously agree on one of the statutory theories of premeditated or felony murder. ( Id. at p. 645.)