Substantive criminal law defines the conduct that the state punishes. Or does it? If the answer is yes, it should be possible, by reading criminal codes (perhaps with a few case annotations thrown in), to tell what conduct will land you in prison. Most discussions of criminal law, whether in law reviews, law school classrooms, or the popular press, proceed on the premise that the answer is yes. Law reform movements regularly seek to broaden or narrow the scope of some set of criminal liability rules, always on the assumption that by doing so they will broaden or narrow the range of behavior that is punished. Opponents of these movements operate on the same assumption - that the law determines who goes to prison and who doesn't, that the distribution of criminal punishment tracks criminal law as it is defined by code books and case reports. Of course, participants in these debates understand that the law does not by itself determine who is and isn't punished. Some criminals evade detection, police and prosecutors frequently decline to arrest or charge, and juries sometimes refuse to convict. Still, if the literature on criminal law is an accurate gauge, all that is just a gloss on the basic picture, a modification but not a negation of the claim that criminal law drives criminal punishment. But criminal law does not drive criminal punishment. It would be closer to the truth to say that criminal punishment drives criminal law. The definition of crimes and defenses plays a different and much smaller role in the allocation of criminal punishment than we usually suppose. In general, the role it plays is to empower prosecutors, who are the criminal justice system's real lawmakers. Anyone who reads criminal codes in search of a picture of what conduct leads to a prison term, or who reads sentencing rules in order to discover how severely different sorts of crimes are punished, will be seriously misled.
William J. Stuntz,
The Pathological Politics of Criminal Law,
Mich. L. Rev.
Available at: https://repository.law.umich.edu/mlr/vol100/iss3/2