By: Benny Agosto, Jr.


New courthouses are built, old courtrooms renovated, and across the state practitioners are using technology in more civil and criminal trials. Many courtrooms are currently equipped with Elmo technology, computers, big screen televisions, and LCD projectors. Multimedia presentations have become increasingly common in nearly all trial settings. Many attorneys now use multimedia audiovisual presentations throughout the trial process, while many more are considering using such technology to enhance their trial presentations.

Computer-generated animation, as demonstrative evidence used to explain or illustrate a witness’ testimony, is a powerful evidentiary tool that must be used with care. Because of its dramatic power, the trial attorney must carefully scrutinize demonstrative evidence for proper foundation, relevance, accuracy, and the potential for undue prejudice. This article will review recent court decisions and prepare the trial practitioner for the evidentiary issues that may arise from the decision to include computer-generated animation in a trial presentation.


Many studies, articles, and books have attempted to explain why demonstrative evidence works. For the trial practitioner, common sense confirms that without a doubt, demonstrative evidence makes a presentation more interesting and memorable. Keeping the attention and focus of jurors during trial is always a challenge. The mind of the average juror tends to wander, especially when the trial presentation involves the reading of a long deposition or viewing a long portion of a videotaped deposition. By introducing demonstrative evidence in the form of computer-generated animation, the trial practitioner can bring to life evidence that would otherwise be boring and tiresome.

It is well settled that demonstrative evidence makes a presentation more memorable to the jury. McGraw-Hill published a well known and universally accepted study regarding information retention, which affirmed what most trial practitioners already knew: “Seeing is believing.” Simplifying complex information and evidence through animation for a jury can be very effective and convincing. A 1992 study, known as the Weiss-McGrath report found “a one-hundred percent increase in juror retention of visual over oral presentations and a six-hundred percent increase in juror retention of combined visual and oral presentations over oral presentations alone.” (Source: Weiss-McGrath report, 1992).

The study was designed to evaluate specifically how individuals retain information. The study compared retention of information presented in three different formats: (1) orally only; (2) visually only; and (3) visually and orally. After the initial presentation of information, the study measured information retention at various intervals. After 72 hours the group presented information solely by oral means retained only 10% of the total presentation. The group receiving information solely by visual means retained twice the information, or 20% of the total information presented. But those who received information both orally and visually retained 65% of the total presentation. The authors of the study concluded that presentations using both visual and oral stimuli result in increased information retention over a longer period of time than presentations utilizing only visual or oral elements.

Why Use Demonstrative Evidence?

According to the Weiss-McGrath study published by McGraw-Hill, there is a dramatic increase in retention after SEEING AND HEARING versus just SEEING or just HEARING the same information.

HearingAfter 3 hours70% retention
HearingAfter 72 hours10% retention
SeeingAfter 3 hours72% retention
SeeingAfter 72 hours20% retention

(Source: 18th Annual Advanced Civil Trial Course, State Bar of Texas, 1995)


A trial practitioner can generally present demonstrative evidence to a jury with little difficulty. Utilizing demonstrative aids in trial requires an understanding of the basic predicates for the admissibility of demonstrative evidence, as well as a presentation that accurately reflects the admitted substantive evidence presented during trial. See Ford Motor Company v. Miles, 967 S.W. 2d 377, 389 (Tex. 1998). To properly admit demonstrative evidence, a trial attorney must meet three requirements: 1) the demonstrative evidence must relate to the admissible substantive evidence; 2) the demonstrative evidence must fairly and accurately reflect the substantive evidence; and 3) that proof must aid the trier of fact in understanding or evaluating the substantive evidence. See Goth v. Continental Oil Company, 678 F. 2d 593, 596 (5th Cir. 1982). A trial judge is given broad discretion in determining whether to admit or to reject demonstrative evidence; the trial judge’s ruling may only be overturned with a finding of clear abuse of discretion. Id.; See also Creating and Presenting Persuasive Demonstrative Evidence by Andy Payne, Advance Personal Injury Loss Course, State Bar of Texas (2002).


Computer-Generated Animations/Out-of-Court Experiment Video

It is well settled that when an experiment or demonstration is conducted out of court and out of the presence of opposing counsel, the evidence offered must be substantially similar to the actual facts of the case. See Horn v. Hefner, 115 S.W.3d 255, 256 (Tex.App.-Texarkana 2003, no pet.) see also Fort Worth and Denver Railway Company v. Williams, 375 S.W.2d 279, 281-282 (Tex. 1964). However, the conditions depicted in a video presentation do not need to be identical to the facts of the contested case. Id. When dissimilarities exist but are minor or easily explained to the jury, the admission of the experiment is within the trial court’s discretion. Id. at 257. It is within the discretion of the trial court to determine whether the existence of a dissimilarity between those conditions causes evidence of the experiment to confuse rather than aid the jury and therefore, whether the evidence should be excluded. Id.; see also Williams at 282; Sosa by and through Grant v. Koshy, 961 S.W. 2d 420, 430 (Tex.App.-Houston [1St District] 1997, pet. den’d).

The standard requiring “substantial similarity” between the animation/experiment and the actual event was first developed in Fort Worth and Denver Railway Company v. Williams. See Williams at 281. In Williams, an automobile train collision caused the death of the plaintiff Fort Worth Railway introduced into evidence a motion picture film of an experiment made by their attorney. The experiment attempted to demonstrate that a beam of light similar to one emitted by a locomotive would cause a “wall of light,” obstructing the view of a driver approaching the beam. Id.

In Williams, the Supreme Court held that the admissibility of the experiment testimony was within the trial court’s discretion because the differences between the experiment and the actual event were minor and could be explained to the jurors without confusing them. Id. at 282. The Supreme Court reversed and remanded for a new trial. Id. at 284.

In Williams, there was no explanation to the jury concerning the differences between the admitted video and the actual event. To ensure fairness, the Texas Supreme Court remanded the case for a new trial so all the evidence could be fairly considered. Id.

Several courts of appeals have tackled the issue of whether an experiment video was substantially similar to the actual events of a case. See Horn v. Hefner at 257 (citing Koshy, 961 S.W. 2d at 430) (holding no abuse of discretion because the expert was cross-examined after the differences between the video and the actual event); University of Texas v. Hinton, 822 S.W. 2d 197, 203 (Tex. App.-Austin, 1991, no writ) (holding no abuse of discretion because differences were explained to jury); Lopez v. Foremost Paving, Inc., 796 S.W. 2d 473,481 (Tex. App.-San Antonio, 1990, writ dism’d) (finding an abuse of discretion because there was no explanation between the differences and the actual event); City of Dallas v. Cox, 793 S.W. 2d 701, 731 (Tex. App.-Dallas, 1990, no writ) (holding no abuse of discretion because differences were explained to the jury); Garza v. Cole, 753 S.W. 2d 245, 247 (Tex. App.-Houston [14th District] 1987, writ ref’d n.r.e.) (holding no abuse of discretion because there was testimony explaining the differences between the video and the actual event). It must be noted that these decisions all hinged on whether the differences between the experiment video and the actual event were adequately explained to the jury. Horn v. Hefner at 257 (citing Williams). Id.

The trial practitioner should review some or all of the following cases when considering presenting computer-generated animation at trial.

Pittman v. Valadez

In 1958, the Texas Supreme Court heard Pittman v. Valadez, a case involving the owner of a truck who brought an action against the driver of a pickup truck for damages incurred in a head on collision. Pittman v. Valadez, 312 S.W. 210 (Tex. 1958). After the initial filing of the lawsuit, the driver of the pickup truck filed a cross-action against the truck driver for personal injuries. At trial, the jury heard the evidence and reached a verdict for the owner of the pickup and against the plaintiff, the truck driver. The jury awarded the owner of the pickup truck $35,000.00 in damages as a result of the personal injuries sustained. Id. The truck driver appealed.

The main issue on appeal concerned whether or not testimony involving an experiment performed by an expert witness at the scene of the accident could be admitted at trial. The expert testified that after the accident, and up to two days before the date of his testimony, he had observed some fifteen or twenty trucks similar to the type of truck driven by Pittman. The expert staged this experiment near the site of the accident, utilizing a stopwatch to document the activity of truck drivers in the area. Id. at 215.

The witness testified that the speed these trucks were traveling was “around anywhere from 55 to 60 miles.” He also testified that he sat and watched the trucks “topping the hill”, and the hill was three or four hundred yards from where he was seated. Based on his observations, the expert concluded that after observing similar trucks driving at a speed between 50 and 60 miles an hour, the plaintiff’s truck must have crossed over the center line, causing the accident.

The Court of Civil Appeals upheld the admission of the expert’s testimony, finding it permissible to prove the existence or non-existence of a fact by experiments performed under circumstances substantially the same as those existing at the time of the alleged facts. The Supreme Court examined the record and concluded that the so-called experiment was not an experiment at all, but merely an observation of trucks similar to the type of truck involved in the accident. The evidence under attack, opined the Court, was principally inadmissible because the test was made under circumstances not substantially the same as those existing at the time of the occurrence of the collision. The Court held that the evidence failed to pass the relevancy test, and that for experimental evidence to be relevant and admissible at trial there must be some logical connection, either directly or by inference, between the evidence offered and the fact to be proved. Id. at 216.

Fort Worth and Denver Railway Company v. Williams

In 1964 the Supreme Court heard the case of Fort Worth and Denver Railway Company v. Williams, a wrongful death action arising out of a railroad crossing collision instituted by the surviving widow and children of the deceased Mr. Williams against Fort Worth and Denver Railway Company. A jury trial was held, resulting in a judgment in favor of the plaintiffs. The Court of Civil Appeals affirmed the trial court’s judgment after a portion of the damage recovery was remitted. See Fort Worth and Denver Railway Company v. Williams, 375 S.W. 2d 279 (Tex. 1964).

The automobile-train collision that claimed the life of Mr. Williams occurred shortly after midnight on September 16, 1956. The deceased, accompanied by his minor son, was traveling in his automobile on a country highway near the town of Petersburg, Texas. The highway crossed two parallel railroad tracks at an angle of 75 to 80 degrees. Mr. Williams approached the railroad junction from the east while driving in a westwardly direction. The railroad crossing was marked with standard cross-arm signs. Where the highway intersected the railroad crossing, the road was straight, the terrain was level, and no obstructions obscured the view of oncoming motorists. Id.

On the night of the accident, a freight train was traveling north from Lubbock to Childress. Behind it, and traveling in the same direction, was a special passenger train. The freight train stopped on the siding to allow the faster passenger train to pass. As the freight train approached the point where the sidetrack diverged from the main track, the brakeman threw a switch, allowing the freight train to pass onto the siding. After the freight train had stopped completely on the sidetrack, the brakeman threw the switch back to its original position, allowing the passenger train proceeded at a slow rate of speed on the main track. The fireman on the freight train tossed a small flare onto the highway west of the crossing, indicating to motorists that the freight train was blocking the railroad crossing. The brakeman did not place a flare on the highway east of the crossing. Id.

When the passenger train was approximately 1,300 feet from the crossing, the deceased crossed the east main track and drove into the freight train occupying the sidetrack to the west. Mr. Williams died a few minutes thereafter. His son knew nothing of the events immediately prior to the collision, as he was asleep in the back seat of the automobile at the time. Id.

The jury found that the crossing was extra hazardous immediately before the collision. Being extra hazardous, the railway company was required to take additional safety measures to protect those using the crossing. The jury further found that the deceased’s view of the freight train was obscured by the beam of light from the passenger train shining between the vehicle of the deceased and the freight train. Furthermore, the jury did not find the deceased was negligent in continuing to drive into the beam of light. The passenger train was equipped with a stationery 1500 candlepower headlight. It also carried a MARS oscillating (figure 8) light that was operating at the time of the accident. Id.

The Supreme Court held that the trial court erred in receiving into evidence the film of a demonstration made by the plaintiff’s attorney designed to show that a beam of light similar to that cast by a locomotive headlight would cause a “curtain or wall of light” to obstruct the view of a person approaching the light at an angle of approximately 90 degrees. Id.

The plaintiff’s attorney conducted the experiment in question in a public park around 11:30 at night. To simulate the 1500 candlepower headlight of the passenger train, the attorney placed a police barrel light on top of a pickup truck. He then positioned his camera to one side of the beam and attempted to photograph objects on the other side of the beam. He moved his camera in a line parallel to the barrel light’s beam, gradually increasing the distance from the source of the beam. He started exposing the film about 200 feet from the barrel light and finished exposing the film at a distance of 600 to 700 feet from the beam. Id.

Counsel for the railway company questioned the plaintiff’s attorney on voir dire, and again on cross-examination, as to the conditions under which the experiment was conducted. The attorney for the railway objected to the admission of the film into evidence stating that the experiment had not been conducted under conditions substantially similar to those existing at the time of the collision. The court overruled the objection and the jury viewed a film of the demonstration.

Stating the rule for these types of cases, the Supreme Court held that in order to render evidence of an experiment made out of court and outside the presence of the opposing party admissible, there must be a substantial similarity between conditions existing at the time of the occurrence which gives rise to the litigation and those in existence at the time the experiment is conducted. However, it is not essential that the conditions during the experiment be identical to the exact facts of the case. When a dissimilarity exists, testimony of an experiment should be excluded from trial when the results would probably confuse, rather than aid, the jury. When the dissimilarities between the original incident and an experiment are minor or can be made abundantly clear by explanation, determinations of admissibility rest within the discretion of the trial judge. Id. at 281 and 282. Although the Williams court found the experimental evidence highly persuasive, the court held that the experiment did not meet the prerequisites of admissibility required under Texas law. Id. at 283 (Citing in the Pittman v. Valadez, 312 5 .W. 2d 210; New York Life Insurance v. Alman, 5th Cir., 22 F. 2d 98 (1927); McLendon v. State, Florida, 105 So. 406 (1925). See also Sosa by and through Grant v. Koshy, 961 S.W. 2d 420 (Tex. App.- Houston [P t District] 1997, pet. den’d). (Case involving video reconstruction of an accident)

Sosa by and through Grant v. Koshy

The Houston First Court of Appeals in Koshy found that the trial court did not abuse its discretion when it admitted an accident reconstruction video into evidence. See Koshy at 430. On cross-examination, the accident reconstructionist in Koshy admitted that: 1) the video showed no cars in the drive thru even though on the day of the accident there were three or four cars in the drive thru; 2) the video showed a white pickup truck even though Koshy was driving in a car; and 3) the video was made on a sunny day, but the accident occurred on an overcast day. Id. The Court of Appeals found no abuse of discretion because the expert was vigorously cross-examined about the differences between his reconstruction video and the actual events. The court further found that the comparative differences depicted in the footage went to the weight of the testimony, not to its admissibility. Id.

University of Texas v. Hinton

The Austin Court of Appeals found no abuse of discretion concerning the admission of an out of court experiment in Hinton. See Hinton at 203. In Hinton, the plaintiff sued the University of Texas for negligence because the plastic grate from a light fixture fell about five feet and struck Hinton on the head. See Hinton at 199. Hinton introduced a video into evidence that showed a plywood cutout, the size of a plastic grate, falling and striking a dummy. Id. at 202. The cutout represented the plastic grate; the dummy represented Hinton. The University argued the heavier plywood struck the dummy with much greater force than the plastic grate struck Hinton, leaving the jury with an erroneous and prejudicial impression. Id. at 202-203. However, Hinton’s expert testified that the video taped experiment was not meant to be an exact duplication of the incident in which Hinton was injured. Plywood was used in the recreation of the accident, instead of a plastic grate, because the plaintiff could not access a grate similar to the one that fell on Hinton. 203. On cross-examination, the expert testified that the purpose of the exhibit was to show how the grate fell, not how forcefully the grate struck Hinton. The Austin Court of Appeals found there was no abuse of discretion because the differences between the experiment and the actual occurrence were explained to the jury without any evidence of juror confusion. Id.

City of Dallas v. Cox

The Dallas Court of Appeals also found no abuse of discretion when the trial court admitted an experiment video in Cox. Cox at 734. The experiment in Cox depicted a ballistics test, designed to demonstrate the effects of bullets on Cox’s body. The Dallas Court found no abuse of discretion by the trial court because the test involved conditions substantially similar to the occurrence at issue and necessary dissimilarities were explained adequately to the jury. Id.

Lopez v. Foremost Paving, Inc.

The San Antonio Court of Appeals found the trial court abused its discretion by admitting an experiment video in Lopez. See Lopez at 481. The court held the video could have been perceived as a simulated re-enactment of the incident. Id. Further, there was no explanation to the jury of the differences between the experiment and the actual event. Id. The video did not purport to illustrate any specific principal but, according to the defendants, generally demonstrated “how the accident occurred.” Id. What the jurors observed on the video was a pickup truck suddenly veering across visible and obvious center stripe markings into the pathway of a tractor-trailer rig. The producers of the video made no attempt to portray the fog or the darkness in which the accident actually occurred. Id. The impact on the juror’s minds of this dissimilar simulation of the accident could have been considerable. Id.

Garza v. Cole

In Garza, the Houston 14th Court of Appeals held the trial court did not abuse its discretion by admitting video footage of an experiment. See Garza at 247. The Garza video was an accident reconstruction video, buttressed by testimony that weather conditions were similar on the day of the accident, the video was made traveling in the same direction as the appellee and that the vehicle was traveling at the same speed at which the appellee was driving. Id. Witnesses also testified regarding other differences between the video and the facts of the actual incident. The court held these discrepancies were adequately explained and went to the weight of the evidence, not to its admissibility. Id.

Horn v. Hefner

The Court of Appeals of Texarkana in the case of Horn v. Hefner, 115 S.W. 3d 255 (Tex. App.–Texarkana, 2003, no pet.), decided a personal injury case involving a vehicle collision that occurred on October 14, 1996. Horn, a plaintiff in the original suit, contended that the trial court abused its discretion by admitting Hefner’s experiment video into evidence. At trial, the jury returned a jury finding no negligence by Hefner. Id.

In Horn, the Texarkana Court of Appeals agreed with the trial court that the conditions depicted in the video were substantially similar to the actual events of the case; any discrepancies were either minor or adequately explained to the jury. See Horn at 259. The Court of Appeals reviewed the differences between the video and the testimony concerning the actual occurrence and found that most of the differences were explained during the examination and cross-examination of the expert witnesses. The court found that the video served the jury to the extent that it gave them an opportunity to see the scene of the collision. The court further found that with the explanations provided to the jury, the dissimilarities included in the video footage did not create a prejudicial effect on the jury.


List of sources for demonstrative evidence other than animation/recreation videos…

  1. Television News Coverage;
  2. Newspaper Photographs;
  3. Police Photographs;
  4. Medical Examiner Photographs;
  5. Scene Photographs;
  6. Video Interviews of Key Witnesses;
  7. Video Interviews of the Court;
  8. Family and Work Photographs;
  9. Sympathy Cards;
  10. Day-in-a-life Footage;
  11. Aerial Photographs;
  12. All Tapes;
  13. 9ll Tapes;
  14. Home Videos & Movies;
  15. Stock Photography;
  16. Medical Illustrations;
  17. Request for Production Documents.


The successful use of computer-generated animation depends on careful consideration of the facts and details of the case. A collaborative effort between the attorney, the expert witness, and the computer animation specialist will ensure accuracy, a key element for both admissibility and effectiveness at trial. While admissibility is never certain, computer-generated animations that meet guidelines such as those articulated in the above-mentioned cases, have gained general acceptance in courtrooms in Texas and throughout the country. When used as a compliment to expert witness testimony, a computer-generated animation can be an effective tool for jury persuasion, providing a memorable image married to compelling narration. See Generally, “Is Forensic Animation Right for Your Case?” Trial, November 2003, by Steven P. Breaux.