In recent decades, there has been a resurgence of research on criminal justice during the classical Islamic period. Rapid urbanization and a need for state control unsettled rudimentary judicial structures. In stark contrast to the legal framework envisioned by jurists, criminal magistrates acted on administrative precepts coupled with their own discretion. Modern historians have attempted to overcome the lack of surviving case records and immateriality of extant legal treatises with new approaches that compare and contrast legal and literary texts using other sources, such as papyri. However, the roots of this dual legal system, dating back to the late eighth century under the Abbasids, remain a mystery. These caliphs transferred jurisdiction of penal law from judges to their elite corps, the shur?a, who had become both criminal magistrates and the police force. Some scholars, such as Joseph Schacht and Emile Tyan, have touched on this development, positing that it was indicative of the absolutist nature of the Abbasids, but this view reduces the complex political and legal factors inherent in this phenomenon. Surprisingly, answers may be found in a parallel development in the Roman Empire. During the Severan period (193-235), Roman emperors gave exclusive jurisdiction over punitive matters from the jury courts to inquisitorial tribunals known by modern scholars as cognito courts, which were run by state magistrates. These were not dictated by laws or edicts but by each judge’s discretionary authority. Similarly, increasing Roman citizenship, populations, and state intervention in cases that had been previously private prompted these changes. My paper argues that the parallel nature, functions, and origins of the cognito courts and the shur?a demonstrate that the legal transformations of the classical Islamic and Roman world were more analogous than previously thought. I will be utilizing a wide array of sources, such as literary texts, political sources, legal treatises, and papyri records, as well as secondary scholarship on Roman criminal law. Modern Roman historians, such as Peter Garnsey and William Turpin, as well as Abbasid-era authors such as Ibn al-Muqaffa? (d. 749-750), Ab? Yus?f (d. 798), and Mu?ammad Shayb?n? (d. 805), will be central to my argument. An interdisciplinary approach yields a greater comprehension of not only the global trajectories of criminal law but also the broader legal dynamics that occur with expanding populations and a tightening of imperial control.