Abstract

In this paper, I aim to explicate the distinction between ‘unconditional relevance’ and ‘conditional relevance’ as those terms and related concepts are applied in the context of admissibility determinations in modern trials. I take the U.S. Federal Rules of Evidence to be my model in analyzing these concepts, though on my view any reasonable approach to legal evidence will have to distinguish between these concepts and make appropriate provisions for their separate treatment. I begin by explaining how the Federal Rules define and apply the concepts of relevance and conditional relevance, and I present an influential argument due to Vaughn Ball that threatens to undermine the distinction between the two concepts. I then argue that Ball's argument fails and I diagnose that failure. However, building on some insights from a variety of evidence scholars, I argue that the approach to conditional relevance adopted by the Federal Rules is crucially flawed for reasons entirely independent of the ones raised by Ball's argument. I identify the main constraints that, on my view, any reasonable approach to conditional admissibility must obey, and I argue for a specific proposal that obeys those constraints. On my positive view, two pieces of evidence should be admitted under a Conditional Admissibility Principle only when each piece of evidence would survive ordinary admissibility scrutiny, conditional on the admission of the other one. I conclude by considering the question of whether it should also be necessary for the two pieces of evidence to survive admissibility scrutiny together, as an ‘evidential package’; I argue that, though the issue may arise infrequently in practice, there is good reason to impose this additional requirement.