We may think prison sentences conclude the criminal process. But crimes occur inside prisons too. When already-incarcerated people are accused of misconduct, prison officials may pursue criminal prosecution in addition to administrative penalties. Prison disciplinary offenses can thus also become criminal cases that result in new convictions and sentences, piling years onto defendants’ terms. Yet little is known about criminal prosecutions of incarcerated people.

This Article is the first to uncover and analyze the pervasive role prisoner prosecutions play in prison administration nationwide. I draw on original empirical data, including state administrative data obtained through open records requests, ethnographic courtroom observations, and qualitative interviews with sixty-four prosecutors, corrections staff, formerly incarcerated persons, and prisoners’ advocates. I find that the widespread prosecutions magnify the social policy concerns that attend to criminal prosecution writ large, including overcriminalization, extreme sentences, and racial inequality.

But I also find that courtroom adjudication of prison misconduct produces several unexpected effects. As a routine parallel track of adjudication for prison misconduct, prisoner prosecutions upend scholarly assumptions that crime in prisons is rarely treated as a formal legal matter. By offering courts a rare window into prison disciplinary systems, through which they sometimes intervene in them, the prosecutions complicate scholars’ understanding about the lack of legal constraint on prisons’ disciplinary authority. By affording victims of prison violence symbolic redress unattainable through “in-house” discipline, the prosecutions cut against accounts of the growing dominance of instrumental uses of criminal law. And by providing prisoner–defendants unusual opportunities to express their autonomy, the prosecutions show that the process is not always the punishment for marginalized defendants.