The Derivative Relevance of Demonstrative Evidence: Charting its Proper Evidentiary Status
73 Pages Posted: 5 Jan 2007
Demonstrative evidence has been part of the American trial process for well over a century. Cases referencing the use of charts, models, diagrams and the like are legion. There are hundreds of articles and several books which describe and tout the uses of demonstrative evidence. What is missing, however, is a scholarly examination of demonstrative evidence theory, i.e., an analysis that defines the term correctly, explains its supportive role at trial vis-a-vis other forms of evidence, and suggests its proper place in evidence codes. Such examination is necessary because computer generated, movie-quality modern day demonstrative proof is qualitatively different from its static, hand-drawn predecessors. This qualitative explosion has led to inconsistency among courts even as to whether to allow these modern displays can be shown in trial, and certainly as to the rules and restrictions governing their showing when they are allowed. A theory which explains the proper evidential role of demonstrative proof will allow a better understanding of its appropriate use and should help unify its treatment.
It is our premise that demonstrative evidence has a secondary or derivative relevance at trial. That is, a piece of demonstrative evidence cannot, on its own, meet the test of "primary" relevancy, i.e., it cannot make the existence of a fact of consequence more or less probable than it would be without the evidence. A diagram of the house where a burglary took place cannot, on its own, make it more or less likely that a crime occurred or that the defendant committed the requisite acts. But what it can do is make more understandable other admissible substantive evidence which itself meets the test of relevancy, i.e., the diagram can illustrate the expert's written report on the location of the shoe prints matching the shoes of the defendant at the burgled home and the homeowner's testimony of what items had been taken and where they were stored. Hence, demonstrative evidence is any display that is principally used to illustrate or explain other admissible testimonial, documentary or real evidence, or judicially noticed fact. As such, if a proffered piece of demonstrative proof assists the trier of fact to understand better another admissible piece of substantive evidence, and if it passes any requisite probative/prejudice balancing test, then it should be freely used in any phase of trial - during opening, closing, accompanying witness' testimony, etc. - and should be subject to the lowered foundational requirements to which such proof has always been put, i.e., no chain of custody, no personal knowledge, etc. Further, it is our belief that the definition of relevance in applicable evidence codes be amended to allow for the formal admissibility of demonstrative evidence for several reasons, including creating a complete record on appeal, and that, for the most part, such displays should be allowed in the jury room just as with any other piece of admitted evidence.
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