Demonstrative evidence refers to physical objects, graphs, pictures, blow-ups of documents, models and other devices which are intended to clarify the facts for the judge and jury: how an accident occurred, actual damages, medical problems, or methods used in committing an alleged crime. Many of these are not supposed to be actual evidence, but "aids" to understanding and retention of presented evidence in the juror's memories. A judge must decide if the evidence will be merely helpful or will inflame the passions of a jury in a way that will prevent them from deciding an issue impartially. For example, a judge may exclude graphic photos of a murder scene if they would ne more prejudical than helpful to the jury.
Computer simulations may be used as demonstrative evidence, to help the finder of fact to understand the expert's findings, much like a chart or a blackboard. Second, a simulation may be used to hep form the basis for the testimony of an expert. In addition, assuming that the proper foundation can be laid, computer simulations may be allowed into evidence as independent substantive evidence. However, there is little agreement among the courts regarding the admissibility of computer animations.
