A good "doctor" is hard to find: Assessing uncredentialed expertise in assisted injection.

This article examines how laypeople assess uncredentialed expertise in a high-risk practice: assisted injection, in which one person injects another with illicit drugs. In metropolitan areas in the US, about 2.3% of the population injects illicit drugs. Injection assistance is common and recipients of injection assistance are at high-risk for injury, overdose, and infection. Yet little is known about how injection recipients attempt to reduce these risks by assessing their injection provider's expertise. Drawing on ethnographic observations and interviews from 2015 to 2018 with 59 people who inject drugs in San Francisco, California, this article examines how people who need injection assistance assess injection provider expertise. It finds that people use an informal hierarchized decision-tree approach of three measures of trust to assess expertise: strong personal ties, referrals, or professional rhetoric. Using measures of trust to assess expertise minimizes some forms of risk by increasing the chance that injection providers are motivated to help them. However, this strategy offers little protection against technically unskilled providers. Moreover, it may increase health risks because people employ few self-protective strategies in trust-based relationships. This research offers new insights for theorization on expertise and trust in social contexts where high-risk skills are in demand. This approach also has implications for public health research and interventions for reducing risks related to lay medical practices, particularly those in assisted injection.