Reflections on the Admissibility of Demonstrative Evidence

By Tomachukwu N. Acholonu  

Admissibility of Evidence in General

The primary component of admissibility of evidence, in general, is relevance.  American Linen Supply Co. v. M.W.S. Enterprises, Inc.,6 A.D.3d 1079, 776 N.Y.S.2d 387 (4th Dept. 2004).  Evidence is deemed to be relevant if it has a tendency to prove or disprove the existence of any material fact making the determination of the action more probable or less probable than it would be without the evidence.  People v. Scarola,71 N.Y.2d 769, 525 N.E.2d 728 (1988); see also, People v. Lewis, 69 N.Y.2d 321, 325, 514 N.Y.S.2d 205, 506 N.E.2d 915 (1987). 

Aside from relevance, in order for evidence to be deemed admissible it is necessary to weigh the probative value versus the potential prejudicial effect of the proposed evidence.  People v. Ziminski, 34 A.D.3d 507, 823 N.Y.S.2d 519 (2d Dept. 2006).  If the prejudicial effect outweighs the probative value, the evidence is likely to be deemed inadmissible.  In addition to determining the probative value of evidence, a proper foundation must be laid before the evidence will be admitted. United Bldg. Maintenance Associates, Inc. v. 510 Fifth Ave. LLC, 18 A.D.3d 333, 795 N.Y.S.2d 535 (1st Dept. 2005).

Demonstrative Evidence

Currently, trials very rarely progress without the introduction of some form of visual or tangible evidence.  As cases become increasingly complicated for a jury, or even the Court to follow, it is necessary to find ways to simplify the issues.  Demonstrative evidence often serves as the simplifier in those situations.

Demonstrative evidence is used to explain, illustrate or clarify a witness’ testimony and to provide the jury with a greater understanding of the facts at issue in a pending trial. It is often a tangible item that can be touched, held, or viewed.  Like all other evidence, the probative value of demonstrative evidence must outweigh the potential prejudicial effect.  Ultimately, the decision regarding the admission or exclusion of demonstrative evidence is left to the discretion of the trial court.  Once the evidence is admitted, the weight of the evidence is left to the determination of the jury.  Hansen v. Coca-Cola Bottling Co. of New York, Inc., 78 A.D.2d at 848, 432 N.Y.S.2d at 723; see also, Johnson v. Michelin Tire Corp., 110 A.D.2d at 824, 488 N.Y.S.2d at 78. 

Courts have consistently held that differences or inaccuracies between demonstrative evidence and the underlying facts will not bar the introduction of that evidence but will go to its weight, when those differences are explained by the foundation witness or by instruction to the jury.  Flah’s, Inc. v. Richard Rosette Elec., Inc. 155 A.D.2d 772, 773, 547 N.Y.S.2d 935, 937 (3d Dept. 1989). 

In Flah’s, plaintiff brought suit based on injuries sustained from a circuit breaker malfunction.  Plaintiff’s expert sought to display and refer to a diagram concerning the electrical system and components, however, defendants argued that it was an inaccurate depiction of the subject wiring and components.  The Court disagreed with the defendants, holding that the diagram was a fair representation of the electrical system and was therefore admissible to explain or illustrate the testimony in order to assist the jury in comprehending the disputed issue.

Demonstrative evidence may be properly excluded if it is offered solely to elicit a dramatic effect or to arouse feelings of sympathy or antipathy.  Demonstrative evidence will also be excluded where there is no good reason for its admission or where it is clearly irrelevant to the issues in the case. 

Courts have also held that it is not improper to admit demonstrative evidence because it is gruesome or because it may influence emotions provided there is a good and just reason for the use.  People v. White, 211 A.D.2d 982, 621 N.Y.S.2d 728 (3d Dept. 1995).

In People v. White, the Court held that the introduction of tissue from the remains of a rape victim’s aborted fetus was not reversible error, despite the gruesome nature of the remains, as the DNA evidence contained in the remains was relevant and not offered to inflame the passions of the jury. Infra at 986.

As technology continues to morph and advance, Courts have had to allow for the admission of evidence presented in computer generated formats.  Though the technology may change, the basis for admissibility remains largely the same.

Computer-Generated Evidence

Computer generated evidence has been separated into two categories:  demonstrative and experimental.  Computer generated demonstrative evidence involves illustrations of scenes, objects, or events as well as presentations used to illustrate the testimony of expert witnesses.  Computer generated experimental evidence involves enhancing data by performing calculations or measurements or by creating a simulation. Computer Technology in Civil Litigation, 71 Am. Jur. Trials 111 §145.

In order for computer generated evidence to be admitted, it must be directly related to the testimony of the witness that it is meant to clarify.  Aside from withstanding the probative balancing test germane to the admissibility of all evidence, computer generated evidence must surpass other considerations: 

Computer generated evidence must be disclosed to opposing counsel in enough time to allow for cross-examination;

  • The evidence must be relevant;
  • If mathematical or scientific principles are used they must be valid and applicable to the facts of the case;
  • The software program and the hardware must be authenticated; and
  • The probative value must outweigh the prejudicial effect and the likelihood of causing injury, confusion or undue delay.

Computer generated experimental evidence is admissible with a proper, expert based, foundation.  The expert must establish the reliability of the evidence and the means used to produce the evidence.  The proponent must also show that the witness, whose testimony is illustrated, is familiar with the evidence and that the evidence accurately depicts the facts of the case in conjunction with the testimony.  Finally, the standard balancing test must be performed between probative value and prejudicial effect. See, Clark v. Cantrell, 339 S.C. 369, 529 S.E.2d 528, 536 (2000)


Demonstrative evidence is a very powerful trial tool especially in cases that would be complicated for jurors without the assistance of such evidence. Demonstrative evidence whether computer generated, photographic or otherwise can help a trial attorney to simplify complex issues and avoid confusing the jury.  With the continued advancements in technology, courts have allowed flexibility regarding the format and type of evidence that is placed before the jury.  Building upon a strong and basic foundation for the admissibility of evidence in general, courts appear to be well equipped to address, evaluate and decide on the admissibility of demonstrative evidence, now and well into the future.