Don’t Talk To Me Like I’m Five, But Explain It To Me Like I’m Five: A Judicial Perspective On Presenting Complex Scientific Evidence To A Judge And Jury Without Talking Down To Them.

Hon. Donald M. Flack(retired)
J.D. Armstrong Teasdale LLP, USA

Presented at the International Symposium on Fire Investigation Science and Technology, 2018


Fire and Explosion investigators are often called upon to testify in legal proceedings. For this testimony to be useful, it must explain the relevant scientific principles sufficiently for the audience to understand them, as well as how those principles apply to the facts at issue in the particular case. For the testimony to be useful, or relied upon by the judge or jury, it also must be presented in a way that keeps the audience interested. It can be difficult as an expert witness to control your own testimony because you are limited to responding to the questions being asked. But an expert can greatly improve the effectiveness of testimony with thoughtful planning.

This paper discusses a thoughtful approach to preparing to testify more effectively in four steps. First, consider the audience–whether it is a judge or jury; and if a judge, what type of judge. Second, consider the point of the testimony–what is the conclusion you want the judge or jury to reach? Third, determine which specific scientific principles are necessary to draw the audience to that conclusion–it is important to not skip any steps in the analysis but also to not add unnecessary elements to the discussion. Fourth–consider thoughtfully how to best educate the audience on those principles–for example, use appropriate technical terminology but define the terms and then reduce them to a lay person’s language. Finally, watch the audience and react to them– not only will their expressions and body language provide clues to their level of understanding, but they will notice your attention to them and become even more interested.

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