What Makes Evidence Sufficient?

When is a party’s evidence sufficient in a civil case? When is the prosecution’s evidence sufficient in a criminal case? The answers to these questions play several important roles—both practical and constitutional—throughout civil and criminal litigation. As a practical matter, a judicial determination that evidence is insufficient may end a case pre-trial (for example, at summary judgment); may end a trial without getting to a jury (resulting in a judgment as a matter of law); or may overturn a jury’s verdict in a civil case or a guilty verdict in a criminal case. As a constitutional matter, the right to a jury trial in civil cases depends on whether parties have sufficient evidence to get to trial, and criminal defendants have a due process right to not be convicted based on insufficient evidence. Despite the importance of the sufficiency issue, the legal doctrine separating sufficient from insufficient evidence is imprecise and unclear, and judicial reasoning applying the doctrine in particular cases is often frustratingly opaque.

This Article examines the general question of what, if anything, makes evidence sufficient. In particular, the analysis explores whether there are any basic features or criteria that underlie or ground sufficiency determinations in civil and criminal cases. The Article first diagnoses the primary reason for the lack of clarity surrounding sufficiency doctrine—uncertainty regarding the underlying evidentiary standards on which sufficiency doctrine depends. Then, drawing on recent evidence scholarship on the process of proof at trial, the Article identifies three possible answers to the question of what makes evidence sufficient. The analysis demonstrates that two possible answers based on probabilistic criteria are implausible and inconsistent with sufficiency doctrine. The Article defends a third possibility based on explanatory criteria. The central thesis is that “explanatory facts”—i.e., facts about the relationships between the evidence and the explanations offered by the parties—make evidence sufficient or not. Recognizing the role played by explanatory facts clarifies the doctrine in civil and criminal procedure, illuminates the caselaw, and potentially guides and constrains future applications.