Criminal procedure is almost completely constitutionalized; civil procedure is not. Meanwhile, the substance of the law of crimes is not very heavily constitutionalized; neither is the substance of the law of everything else. So constitutional law treats the criminal side of the civil-criminal line as special, but only when crafting procedures. The idea of treating the criminal sphere as constitutionally special may make a lot of sense, but if it does, it makes sense for process and substance alike. Indeed, the point is stronger: without substantive limits, important parts of the law of criminal procedure seem likely to fall apart. We should either de-constitutionalize much of criminal procedure, or create a kind of substantive due process for criminal law.
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