In recent years, the demand for cost-effective evidence of health impact has grown exponentially, often to the exclusion of other disciplines and of epidemiology's longstanding interest in the multivariate determinants of health. Drawing on an ethnography of the Safe Motherhood Initiative, this paper focuses on experts who, in producing historical case-study evidence, exceptionally inhabit a stigmatising epistemological position while still successfully commanding the respect of policy makers. To theorise the sources and effects of this epistemic diversity, we draw on the anthropology and sociology of science, and specifically on Holmes and Marcus' analyses of 'para-ethnographic' modes of reasoning.