"Loyalty trials" are common to a range of conflict settings, with consequences that range from harassment to imprisonment, torture, or death. Yet, they have received little if any attention as a general phenomenon in studies of state repression, civil war, or rebel governance, which focus on particular behaviors that authorities use to put people on trial, such as dissent, defection, and resistance. Using a computational model and data on the German Democratic Republic and the Occupied Palestinian Territories, we focus on the dynamics of "loyalty trials" held to identify enemy collaborators—the interaction between expectations, perceptions, and behavior. We use our framework to explore the conditions under which trials result in widespread defection, as in the German Democratic Republic, or in conformity as illustrated by our study of the Occupied Palestinian Territories. The polarizing nature of loyalty trials and the propensity to over- or under-identify threats to political order have notable implications for democratic and non-democratic societies alike.