In the litigation context the law is the primary judge of ethics for those persons who contribute to the law’s processes. Ethical quandaries routinely are generated via role conflict. Quandaries routinely arise when actions of the agent ethically are the actions of both the agent qua principal (i.e., expert providing evidence in a legal process, thus the expert as “the law”) and the agent acting personally (e.g., expert providing testimony of personal opinion). Who controls choice of ethical action in that context: the principal or the agent? Which ethical responsibilities flow to whom? Expert witnesses encounter both unique and routine role conflicts in a litigation context. These role conflicts spring from experts serving multiple masters (e.g., the law v. client v. profession). The relative priority of these actors can be dynamic as well as conditional upon non-role attributes. This article explores these issues from the perspective of the Federal Rules of Evidence for testimony by lay fact witnesses and for expert opinion witnesses.