What 1252 papal bull is often cited in discussions of inquisitorial procedure and interrogation?

The story behind the answer

Issued by Pope Innocent IV in 1252 amid campaigns against heresy in northern Italy, this bull explicitly authorized inquisitors to employ coercive interrogation under strict limits—no shedding of blood or endangering life—and required cooperation from secular authorities. By codifying procedures for arrest, interrogation, and confiscation of property, it became a key reference point for how the medieval Inquisition conducted investigations.

Its provisions were echoed by later papal directives and filtered into influential inquisitorial manuals, helping standardize methods across Europe. In contrast, similarly named documents often confused with it dealt with very different matters: Ad abolendam (1184) set earlier anti-heresy measures, Inter caetera (1493) divided newly encountered lands between Spain and Portugal, and Regnans in Excelsis (1570) excommunicated Elizabeth I—none centered on interrogation procedures.