Dr. Ken Manges Ph.D. | Forensic Psychologist |Expert Witness

After a thorough investigation and careful preparation of your client’s case, you want the jury to understand the information being presented to them.

One way to enhance the impact of this information is through the use of demonstrative evidence.

Demonstrative Evidence

Demonstrative evidence is any form of secondary proof that explains testimonial, documentary, or concrete evidence.

Demonstrative evidence comes in 1 of 5 forms:

  • The demonstration, recreation, or experiment
  • Chart, diagram, map, or summary
  • Model or other tangible objects
  • Photograph or video
  • Jury viewing

Mediums for demonstrative evidence:

  • Blackboard
  • Sketch pad
  • Model boards and scale models
  • Graphs, charts
  • Overlays, transparencies, projector
  • Photos, videos
  • Motion pictures
  • Computer generated videos
  • Computer generated animation illustrates an expert’s opinion and the position of objects moving through space over time. It plots the paths take by all relative objects throughout the specified time. Action can be shown in real time or slow motion.

Some forms of demonstrative evidence are objective in nature and are helpful in conclusively establishing your case. (i.e. a videotaped confession or an aerial photo of real estate)

Try to use demonstrative aids. Hearing a fact once, the jury may remember it, hearing it several times, they will most likely remember it, but seeing the fact, they will believe it. Communication is based on perception. Objects we can see have higher credibility and are better retained than information only heard.

When presenting demonstrative evidence, use words that divulge details and create specific images.

Consult with your expert witness when preparing for trial regarding the kind of visual aid he/she would like to use.

Techniques for conducting courtroom demonstrations.

  • You are similar to the director of a play – you must set the stage, plan the action, and polish the plot.
  • In many cases, you will want to make the demonstration as dramatic as possible, but take care it unfolds as planned, it is interesting, persuasive, and safe.
  • Two instances you may want to downplay the dramatics – when the event is sufficiently dramatic or when it would appear fake.

When using a spontaneous diagram there are a few factors to consider when choosing an effective medium:

  • How easily can the illustration be made
  • How readily can it be used by the jury
  • How can it be incorporated into the record
  • How and where the diagram will be displayed

Use discretion when producing visual aids.

Be cautious of when a photograph is introduced – it will likely contain extraneous evidence that will be inadmissible as oral testimony.

Be cautious that there are many conditions which can distort a photograph’s image and compromise the “fair and accurate” portrayal (i.e. camera angle, lenses, filters, lighting, printing, developing, etc.)

In some cases, a motion picture, videotape, or voice recorder will become primary evidence itself. Audiovisual devices are not merely an addition to testimony.

Models are extremely effective, yet are very expensive – it may be better to use them in major litigations.

  • One problem with models –if they have working parts, make sure the parts work as they are supposed to work.

“Models and demonstrations can form very forceful pieces of demonstrative evidence. They can also be disastrous if not properly designed and tested before trial. The use of a little imagination and a little effort can result in very effective models and demonstrative aids being developed, which in most cases can be the most important form of visual evidence.”

The actual object involved in the case can be introduced as evidence and can be very useful.

To establish a foundation for admission of a demonstrative exhibit you must show:

  • The exhibit relates to other relevant, competent, and material testimonial, documentary, or real evidence.
  • The witness whose testimony the exhibit illustrates should be familiar with the exhibit.
  • The demonstrative aid fairly and accurately reflects the evidence to which it relates.
  • It will aid the judge &/or jury in understanding and evaluating the related evidence.

The principle of admissibility is the same regardless of whether the object is a photograph, drawing, painting or mosaic. The main point is whether the witness has personal knowledge of the subject matter, saw the event in question and the visual representation is a fair and accurate portrayal of the true scene.

Differences between Demonstrative Evidence and Substantive Evidence:

Demonstrative Evidence:

  • Cannot independently prove a fact – can only illustrate or explain other testimonials, documentary, or real proof
  • Is usually prepared for litigation
  • Can be admitted at trial even if it only helps explain a piece of substantive evidence already introduced
  • It only needs secondary relevance
  • Does not have to be formally admitted
  • Can be included on the record on appeal

Substantive Evidence:

  • Can generally be independent
  • Can be admitted if it tends to prove the apparent existence or non-existence of a relevant fact
  • It must have primary relevance
  • Should be formally admitted

For References used in this fact sheet, please contact Dr. Manges & Associates, Inc.

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