To this day, judges and advocates struggle with the definition and use of demonstrative evidence. The ambiguity of this term (or its close cousins illustrative evidence and evidence offered for illustrative purposes only ) infects the judicial process with uncertainty, hindering advocates when preparing for trial and, in some cases, producing erroneous verdicts. For example, the Seventh Circuit recently reversed a case for improper use of a demonstrative exhibit, and on retrial the result swung from a defense verdict to an $11 million plaintiffs victory. Uncertainty about the admission and use of demonstrative evidence has festered for decades. Lawyers innovate in presenting their cases, forcing judges to make case-by-case rulings. Thi...