Demonstrative Evidence: How It Can Help Expert Testimony

Numerous studies have indicated that jurors respond well to visuals, and that graphic evidence drastically increases their rate of information retention from 10% to 87%. Because the average juror is more likely to remember what they see rather than what they hear, it is helpful to incorporate visual depictions of evidence whenever possible. Particularly when offering an expert opinion, such demonstrative evidence can enhance the expert’s testimony by helping the jury better understand the facts at issue.

Demonstrative evidence generally refers to evidence that offers a physical illustration of a fact presented, rather than a verbal description. While real evidence is substantively used to prove a fact at issue in the case, demonstrative evidence is used to clarify, explain, and offer a visual aspect of the presentation.

Demonstrative evidence can come in many forms—photographs, video animations, graphs, diagrams, charts, slideshows, drawings, computer graphics, and simulations—the list goes on and on. The advent of three-dimensional computer-generated technologies, such as virtual reality and augmented reality programs (the latter of which overlays virtual, 3-D images over the real-life environment) has taken demonstrative evidence to a whole new level.

When is it Beneficial to Use Demonstrative Evidence?

By definition, an expert’s purpose is to help the trier of fact understand the evidence or determine a fact in issue. See Rule 702 of the Federal Rules of Evidence. As such, demonstrative evidence should work as an extension of the expert by offering a visual representation of the expert’s testimony. Demonstrative evidence should only be used if it strengthens the expert’s testimony. Ideally, the evidence should help the jury understand relevant facts that would otherwise be difficult to comprehend without the aid. Demonstrative evidence may also be used to emphasize important aspects of the testimony. The ways in which a demonstrative exhibit may be helpful at trial are as varied as the types of evidence themselves.

In criminal trials, for example, demonstrative evidence can illustrate the scene of the crime, and in some instances, may be able to prove guilt or innocence. Photographs or recreations of a victim’s injuries, blood spatters, or footprints are just a few examples of illustrations that can prove—or disprove—a case.

In cases involving personal injuries sustained as a result of an accident, demonstrative evidence in the form of a reconstruction can be particularly helpful. While an accident reconstruction specialist testifying to the cause of a vehicle collision may base their testimony on a number of scientific methods (such as energy analysis and time distance analysis), such technical principles may be difficult to follow when described in verbal testimony. A visual reconstruction, which can be as simple as a scaled drawing of the scene or as complex as a virtual reality reconstruction of the size and speed of the vehicles, can help bring the testimony to life.

Similarly, most medical experts stand to benefit from demonstrative evidence, as oftentimes their testimony is complex in nature. When discussing a party’s injuries, for example, the expert can use photographs or graphic models to pinpoint the affected areas. Life-size replicas of the anatomy are also sometimes used to explain the causes of injury. Technology in this field is rapidly advancing and should be utilized whenever feasible. For example, the medical school at the University of California, San Francisco uses virtual reality headsets to examine computer-generated cadavers and inspect the anatomy without ever touching an actual human body. The body can be examined at different angles and microscopic areas can be observed by simply enlarging the view.

The virtual examination of a body offers a number of benefits during expert testimony. It is a realistic, detailed demonstrative aid that avoids the logistical issues of life-size anatomical models that would need to be passed to each juror to obtain a full view.

That being said, not all demonstrative evidence is failsafe. Sometimes, in an effort to create the most informative aid, the actual information gets lost in the shuffle (i.e., graphs packed with small text that cannot be clearly read). Also, in the case of computer-generated graphics or other hyper-realistic imaging, some jurors may experience cognitive overload if the exhibit is too flashy or “busy.” As a logistical matter, some aids simply won’t work in certain courtrooms. For example, an elaborate computer simulation will be stopped in its tracks if the courtroom is not equipped with the correct wiring to connect the computer to the projection screen. Therefore, it is important to remember the practical limitations—of both the jury and the court—when deciding which aid to use.

The Admissibility of Demonstrative Exhibits

Like any other exhibit offered at trial, demonstrative evidence is subject to the applicable evidentiary rules of the jurisdiction. The proper foundation needs to be established in order to successfully admit the exhibit into evidence at trial. Laying the foundation of a demonstrative exhibit through an expert witness should consist of questions that establish its authenticity such as: Is this exhibit a fair and accurate depiction of what it intends to portray? Does this exhibit help explain your testimony to the jury? For example, a visual reconstruction of a car accident should accurately portray how the scene looked at the time of the incident. The general rule is that demonstrative evidence should truly help the jury understand the facts.

The Federal Rules of Evidence are relatively scant on specific references to demonstrative evidence. Rule 611 permits the courts to “exercise reasonable control over the mode and order” of presenting evidence so as to make the procedures effective for determining the truth and to avoid wasting time. Rule 1006 permits the use of “a summary, chart, or calculation to prove the content of voluminous writings, recordings, or photographs that cannot be conveniently examined in court.” In other words, demonstrative exhibits can be used to summarize otherwise voluminous evidence (i.e., a chart highlighting key relevant portions of writing), but the mode and order in which it is presented is ultimately at the discretion of the judge.

Demonstrative aids are also subject to the applicable relevancy rules. Under Rule 401 of the Federal Rules of Evidence (and under certain state laws that have adopted such a rule), evidence is deemed relevant if it has any tendency to make a fact more or less probable than it would be without such evidence and the fact is of consequence in determining the action. Under Rule 403, a judge may exclude otherwise relevant evidence if its probative value is substantially outweighed by the danger of “unfair prejudice, confusing the issues, misleading the jury, undue delay, wasting time, or needlessly cumulative evidence.”

Due to the influence that visual evidence tends to have on a jury, an opposing party may object on any of the above grounds (i.e., graphic photographs of a murder victim in a criminal trial may unfairly inflame the jury, or several exhibits summarizing the same information may be considered a cumulative presentation of evidence).

Overall, when effectively utilized, demonstrative evidence and visual aids can enhance an expert’s testimony in ways that solely oral testimony cannot.