7 Principles For Creating Credible and Admissible Forensic Animations

by Nathan Rose, Director and Principal at Kineticorp


An animation can provide tremendous value to a jury by making an expert’s opinions more understandable. In this article, I will give you 7 principles for producing credible and admissible animations for use in depositions, mediations, settlement conferences, and trials.

These are the same principles that I and others in my firm have used to develop numerous animations that have been admitted in trials across the United States.


Here is an example of the type of animation I’m addressing:


I am a director and principal accident reconstructionist at Kineticorp in Denver, Colorado. We specialize in accident reconstruction and visualization and have used animations to explain technical concepts to juries on many occasions.

We have consistently had our animations admitted.

My own personal expertise is in the area of vehicular accident reconstruction, and so, I’m going to develop this article from that perspective. However, these principles are applicable to other types of animations as well. For example, Graves gives the example of using an animation to explain the inner-workings of a handgun [2000].


In a litigation context, animations are often intended to be a demonstrative exhibit to help an expert explain their opinions. Modern jurors are sophisticated and accustomed to high-quality television, video, and animation production. They are accustomed to a high level of physical realism, and so, realism in an animation will help to build credibility for an animation.

Physical realism begins with having objects in the animation that are correctly sized relative to one another. Jurors will perceive errors in scale and this will give them cause to doubt the credibility of the animation.

Beyond the benefit to the jury, the process of putting together an animation in an accurately-scaled computer environment can help the expert to develop their opinions by helping them to understand how objects fit together and interact [Hull, 1992; Fay, 1996]. An example would be analysis of how two vehicles collided by creating accurately-scaled models of the vehicles and their damage in a computer animation software package. Another example would be using correctly scaled objects to evaluate geometric visibility for a driver in an accident.


Oftentimes, the animations that I am showing in a trial depict a car crash. Car crashes typically leave physical evidence – tire marks, gouges, debris, and vehicle damage. The vehicle rest positions are also typically known. The vehicle motion that I show in an animation will be credible to the extent that it is consistent with the physical evidence and explains how that evidence was actually created.

In other words, when I analyze a crash, I’m using the physical evidence to determine what happened. The animation that I create out of that process should reveal to the jury how that evidence was created – my explanation for that evidence. I want to give the jury a trial exhibit that helps them understand the case better.

If my animation helps the jurors understand the physical evidence better, then it will provide them with value. And, of course, the value an animation provides to a jury is one of the criteria for its admissibility (see Jones [1991] and Hull [1996], for instance).


Most every accident reconstructionist will tell you that eye-witnesses are not good at estimating times, speeds, and distances. That should, of course, be acknowledged. However, the stories that witnesses tell about an accident can sometimes be very credible.

An accident reconstructionist should not dismiss the story that a witness tells without some systematic examination of that story. If physical evidence and physics compel an accident reconstructionist to dismiss what a witness says, fine. Otherwise, the animation should be as consistent with that testimony as possible – within the confines of physics and physical evidence. (For more related to this principle, see my article Use Physics and Evidence to Test What Witnesses Say About a Crash)


Again, modern jurors are accustomed to physical realism in the media they consume. In an animation of a vehicular crash, the motion of the vehicles is going to be perceived as more realistic if that motion is grounded in physics. In the animation I showed at the beginning of this article, much of the vehicle motion was produced using a software package called PC-Crash, a physics based accident simulation software. This physics-based motion gives the animation credibility because the motion of the vehicles looks and feels right. (Here is a link to a recent court ruling admitting analysis with PC-Crash: http://www.kineticorp.com/pc-crash-ruling.pdf)

As Grimes [1992] has noted: “Unfortunately, the word ‘animation’ is often associated with cartoons, where objects are not bound to the laws of physics. In contrast, an accurate depiction of a collision requires the animation to be consistent with the physical laws-of-motion. Computer animation requires sufficient data to produce all the images of the vehicle traveling through the collision scene. Therefore, credible animations must be based upon a detailed reconstruction of the collision sequence.” In 1994, Grimes proposed the term “scientific animation” to describe an animation in which the objects are properly scaled and the depicted motion obeys the laws of physics. Also in 1994, Day used the term “scientific visualization” to refer to animations in which the underlying vehicle motion is generated by a physics-based simulation software package. In 1998, Grimes defined scientific visualization as “a computer animation in which the motion of the primary objects is based on scientific analysis or scientifically accurate equations.” By this definition, the animation I showed at the beginning of this article is a scientific visualization.

(See Martin [1991] for a dated, but still relevant application of this principle. See Massa [1996] for sample techniques related to critiquing the physical realism of an animation.)


Many vehicles now record electronic crash-related data and analysis of this data is usually a part of an accident reconstruction. The engine control module on the semi-tractor in the animation I started this article with recorded crash related data (speed, for instance) and we were able to use that data in producing the motion of this tractor for the animation. This essentially relates back to the principle of tying the animation to the physical and testimonial evidence.

The electronic data on modern vehicles is another source of evidence about the crash and an animation that is consistent with the known evidence will be more credible than one that is not.


Car crashes occur at a particular time and place. Including accurate secondary details about the scene, such as road signs, vegetation, correct lighting, and logos on vehicles can add credibility to an animation. In the animation I showed at the beginning of this article, I have removed a number of the secondary details. However, if I was showing this animation in a trial, these details would be included. This is mostly a physical realism issue. It is important to distinguish between primary and secondary details – or essential and nonessential details [Hull, 1996]. Animations can be reliable and admissible without the secondary (non-essential) details. However, including these secondary details will help orient the jury and will give the jury a sense that that you understand the context in which a crash occurred [Grimes, 1992 and 1994].

Grimes [1998] distinguishes between primary and secondary details as follows: “The basic difference is that primary objects are important to the purpose of the presentation and secondary objects are only for helping orient the audience.”


While physical realism can add credibility to an animation, a jury should not be left with the impression that they are actually watching the real events. Animations are often a demonstrative exhibit that illustrates an expert’s opinions. A transparent presentation of the process through which the animation was created will help the jury understand the accident better, but will not leave them with a misunderstanding of what they are actually watching. By a transparent presentation, here’s what I mean: present the physical evidence, present your analysis of the physical evidence, present how you have brought principles of physics to bear on the physical evidence, and then present how physical evidence and physics flow directly into the animation.

Transparent presentation of the process also helps lay the foundation for an animation, making it more likely to be admitted. Along these lines, Grimes [1998] argues that “any presentation that is presumed to be based on scientific principles should be thoroughly documented such that a similarly qualified person can reproduce the findings.” Fay [1997] covers several examples of cases in which animations were either admitted and excluded.

by Nathan Rose, Director and Principal at Kineticorp



  1. Day, Terry D., “The Scientific Visualization of Motor Vehicle Accidents,” SAE Technical Paper Number 940922, doi:10.4271/940922.
  2. Fay, R.J., Gardner, J., “Analytical Applications of 3-D Imaging in Vehicle Accident Studies,” SAE Technical Paper Number 960648, doi:10.4271/960648. [Fay discusses analytical purposes for animations that go beyond illustrating an expert’s opinions.]
  3. Fay, R.J., “Computer Images and Animations in Court,” SAE Technical Paper Number 970965, doi:10.4271/970965.
  4. Galves, Fred, “Where the Not-So-Wild Things Are: Computers in the Courtroom, The Federal Rules of Evidence, and the Need for Institutional Reform and More Judicial Acceptance,” Harvard Journal of Law and Technology, Volume 13, Number 2, Winter 2000.
  5. Grimes, W.D., “Computer Animation Techniques for Use in Collision Reconstruction,” SAE Technical Paper 920755, doi:10.4271/920755.
  6. Grimes, W.D., “Classifying the Elements of a Scientific Animation,” SAE Technical Paper 940919, doi:10.4271/940919.
  7. Grimes, W.D., Dickerson, C.P., Smith, C.D., “Documenting Scientific Visualizations and Computer Animations Used in Collision Reconstruction Presentations,” SAE Technical Paper 980018, 1998, doi:10.4271/980018.
  8. Hull, W.C., Newton, B.E., “The Animation Computer as a 3-D Reconstruction Tool,” SAE Technical Paper 920754, 1992, doi:10.4271/920754.
  9. Hull, W.C., Newton, B.E., Macaw, C.R., Miller, R.R., “Functional Classifications and Critique Methods for Litigation Support/Accident Reconstruction Animations,” SAE Technical Paper 960651, 1995, doi:10.4271/960651.
  10. Jones, Ian S., Muir, D.W., Groo, Stephen W., “Computer Animation – Admissibility in the Courtroom,” SAE Technical Paper 910366, 1991, doi:10.4271/910366.
  11. Martin, K.F., Banister, J.A., Piziali, R.L., “Engineering Visualization of Vehicle Accidents: Data Sources and Methods of Production,” SAE Technical Paper 910369, 1991, doi:10.4271/910369.
  12. Massa, David J., “Using Computer Reverse Projection Photogrammetry to Analyze an Animation,” SAE Technical Paper 1999-01-0093, 1999, doi:10.4271/1999-01-0093.
  13. McLay, R.W., Kiely, S.J., Sheehan, M.L., “Case Studies in Animation Foundation,” SAE Technical Paper 940920, 1994, doi:10.4271/940920. [McLay discusses purposes for animations other than simply illustrating an expert’s opinions.]