Why were Dominican and Franciscan friars often chosen as medieval inquisitors?

Dominican and Franciscan friars were frequently appointed as inquisitors during the 13th century because the existing episcopal inquisitions—led by local bishops—had proven ineffective due to the regional nature of a bishop's power and inconsistent implementation across dioceses.1

The papacy turned to the mendicant orders for several key reasons:

• Mobility and Reach: Unlike static monks or local clergy, the friars were highly mobile and well-trained, allowing them to reach and influence populations that the established church had failed to persuade.2
• Learning and Piety: The friars were recognized for their initiatives in learning, probity, and piety. They held theological chairs at major universities and were viewed as a learned and respectable counter-ministry capable of challenging the intellectual arguments of heretical groups like the Cathars.345
• Institutional Organization: Both the Dominican and Franciscan orders were highly organized with international administrative structures, which provided a level of consistency and coordination that individual bishops lacked.34

By commissioning these friars as papal judges delegate, the church established a more effective, centralized approach to identifying and addressing heresy.1