evidentiary foundations

Out-of-Court Experiments — Laying an Evidentiary Foundation

evidentiary foundationsPlanning to introduce evidence of an out-of-court experiment at your next trial? An out-of-court experiment is a highly effective way to convince a jury that your theory of the case is correct.  But your evidence may never get to the jury unless you first lay a proper evidentiary foundation.

In this excerpt from his book Trial Evidence Foundations, highly-regarded Rhode Island trial attorney Gordon Cleary lays out for you the necessary elements.

The Expert’s Qualifications

  • The expert witness must possess the necessary expertise to design and conduct the out-of-court experiment.
  • The witness must be qualified as an expert in the relevant field (e.g., accident reconstruction, product design, etc.).

Testimony About the Expert’s Assignment

  • The witness testifies that the proponent asked the witness to design and conduct an experiment.

Note: Because the request is not an assertive statement, it is not hearsay and, therefore, the witness may testify that he or she complied with the request without violating the hearsay rule.

Testimony About Designing the Experiment

The witness describes how he or she first studied the relevant facts and then conducted the out-of-court experiment in an attempt to duplicate applicable circumstances:

  • the expert can rely on personal knowledge (site visit);
  • the expert can rely on facts submitted to the expert at trial (in the form of hypotheticals) or other discovery materials submitted;
  • the expert can rely on hearsay sources of information.

Note: Under Fed. R. Evid. 703, the expert may gain his or her information about the incident from each of these three sources (singularly or in combination).

  • After studying the incident, the witness identified the requisite variables that would have to be duplicated in order to replicate it.

Note: The witness may also have to identify any scientific hypotheses on which he or she relies in determining the outcome of the experiment.

  • The witness testifies as to how the experiment was designed to ensure that the experimental conditions were substantially similar to those that occurred at the time of the incident.

Note: Although the two sets of conditions might not be absolutely identical, there should be sufficient similarity in essential and critical aspects.

Testimony About Conducting the Experiment

  • The witness testifies that he or she conducted the experiment (either in person or supervising the experiment as it is conducted by others).

Note: Here, again, any instructions that the witness gave or received about how the experiment should be conducted would also be non-hearsay because they are acts and imperative sentences. Moreover, even if the expert did not personally conduct the experiment, the expert could rely on the hearsay reports of other participants under Rule 703.

Testimony About the Results

  • The experiment led to a particular result. The expert witness should describe the outcome of the experiment (from first-hand personal knowledge); the expert could, for example, authenticate a photograph or videotape of the experiment.
  • The expert explains how the photograph or videotape will assist the trier of fact in understanding the expert’s testimony, and how the photograph or videotape is consistent with what the expert observed or learned about the out-of-court experiment.


About the Author

Gordon P. Cleary is a trial attorney with more than 30 years’ experience. He practices in the areas of federal litigation and general civil litigation, including commercial law, air carrier liability, admiralty, intellectual property, and American Indian law. Mr. Cleary speaks and writes frequently on discovery and deposition techniques, trial evidence, and trial practice and procedure, and has served as a faculty member of the Massachusetts Continuing Legal Education/Massachusetts Law Institute Trial Advocacy Program.