Legal & DebateDUAL-USE

Demonstrative Evidence

What it is

Charts, diagrams, models, timelines, animations, and in-court demonstrations that illustrate testimony rather than prove facts on their own, admitted at the judge's discretion because they help the jury understand and controlled because they can also distort.

How it works

Demonstratives work through the picture-superiority effect and concreteness: a timeline is remembered when a list of dates is not, and a computer animation of a collision is experienced as having been seen rather than described. That is their value and their danger. Federal Rule of Evidence 611(a) gives the court control over the mode of presenting evidence, and Rule 403 lets it exclude an exhibit whose illustrative value is outweighed by unfair prejudice or by the risk of misleading the jury. Kassin and Dunn (1997) found that computer-animated displays helped mock jurors when the animation matched the physical evidence and pulled verdicts toward the animation when it did not. Feigenson and Spiesel document how digital displays lend testimony an authority it has not earned, because the jury takes the image as the event. The rules respond with foundation requirements (a witness must testify that the exhibit fairly and accurately depicts what it purports to show), with limiting instructions that demonstratives are aids and not evidence, and with the adversary's right to attack the assumptions behind the picture.

Real-world examples

  • •The glove demonstration in the 1995 Simpson trial is the standard warning about in-court demonstrations: the prosecution had the defendant try on the gloves, they appeared not to fit, and the moment became the defense's theme.
  • •"Day in the life" videos, showing a plaintiff's routine after a catastrophic injury, are admitted in many courts with limits on length, narration, and staging, because their emotional force is exactly what Rule 403 balances against their value.
  • •Dueling accident-reconstruction animations are routine in vehicle and aviation cases, and the fight over them is usually about the inputs (speeds, sight lines, reaction times) supplied by each side's expert rather than about the animation itself.
  • •Kassin and Dunn (1997): a computer animation of a disputed fall shifted mock jurors' judgments toward the version the animation depicted, including when the physical evidence pointed the other way.

Ethical guidelines

Where the line is

An illustration that accurately renders the evidence and is labeled as an aid helps jurors understand testimony they could not otherwise follow; an exhibit engineered so that its scale, omissions, or animated assumptions carry a conclusion the evidence does not support turns a teaching tool into testimony no one gave under oath.

  • ●A demonstrative must fairly and accurately represent the testimony or data it illustrates; an exhibit built on contested assumptions should display them, and counsel who present a "scale" drawing that is not to scale or a timeline that omits events invite exclusion and a credibility collapse.
  • ●Demonstratives are ordinarily disclosed to opposing counsel before use so that objections can be heard outside the jury's presence; springing an exhibit is trial by ambush in visual form.
  • ●Animations and simulations require expert foundation for their inputs (Rule 702) and usually an instruction that they illustrate an opinion rather than record an event.
  • ●Educational; rules vary by jurisdiction; not legal advice.

How to defend against it

  • ►Jurors: ask of every chart and animation "who made this, from what data, and what did they leave out?"; the exhibit is only as good as the testimony under it, and the instruction that demonstratives are not evidence means you may discount them entirely.
  • ►Jurors: notice the difference between a photograph of the scene and a reconstruction of the event; the second is someone's opinion rendered as a picture.
  • ►Opposing advocates: obtain the underlying data and assumptions in discovery, cross-examine the inputs rather than the picture, ask for the limiting instruction, and where the exhibit misleads, move under Rule 403 before it is shown.
  • ►Witnesses: if asked to confirm that an exhibit fairly and accurately depicts something you know, look at it carefully and say what is wrong or missing; your foundation testimony is what admits it.

References

  1. Kassin, S. M., & Dunn, M. A. (1997). Computer-animated displays and the jury: Facilitative and prejudicial effects. Law and Human Behavior, 21(3), 269-281
    Animations aid understanding when consistent with physical evidence and bias verdicts when inconsistent with it.
  2. Feigenson, N., & Spiesel, C. (2009). Law on Display: The Digital Transformation of Legal Persuasion and Judgment. New York University Press
    How digital visual displays shape legal judgment and acquire unearned authority.
  3. Federal Rules of Evidence (2011). Rule 403. Excluding Relevant Evidence for Prejudice, Confusion, Waste of Time, or Other Reasons. Federal Rules of Evidence (restyled 2011), Legal Information Institute · link
    Exclusion of exhibits whose value is substantially outweighed by unfair prejudice or the risk of misleading the jury.
  4. Federal Rules of Evidence (2011). Rule 611. Mode and Order of Examining Witnesses and Presenting Evidence. Federal Rules of Evidence (restyled 2011), Legal Information Institute · link
    The court's control over the mode of presenting evidence, the basis for regulating demonstratives.
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