Justice Black agreed that the judgment denying habeas relief should be reversed, but he rejected the Court's constitutional invalidation of New York's jury procedure. In his view, juries are constitutionally trusted factfinders, and allowing them to decide voluntariness along with guilt does not itself deny due process. He feared that requiring a judge first to make a final voluntariness finding both diminished the jury's historic role and rested on unsupported assumptions that jurors, more than judges, would disregard instructions.
He also criticized the majority's reliance on a broad conception of Fourteenth Amendment due process that lets the Court invalidate state procedures merely because it considers them unfair. For Justice Black, due process required adherence to the law of the land and explicit constitutional guarantees, not judicial revision of state criminal procedure.
On the merits of Jackson's confession, however, Justice Black would have held the later hospital statement involuntary as a matter of law. Jackson was gravely wounded, had lost substantial blood, had just received sedating drugs, was denied water, was surrounded by police without counsel or friends, and was questioned immediately before surgery. Those circumstances, in his view, were inherently coercive.
Justice Black would have ordered Jackson's release unless New York set aside the conviction and afforded him a complete new trial. He objected to the majority's limited remand for a later voluntariness hearing as an impermissible piecemeal prosecution that unnecessarily fragmented the criminal case.