Cross Examination of the Defense Expert

Think of a trial as a mosaic, with each part intertwined intricately with the others: opening statements, direct examination, cross examination, and closing arguments. In order to have successful closing arguments, you must have a successful cross examination. In order to have a successful cross examination, you must have set the stage appropriately and framed the case correctly.

Part of setting the stage and framing the case is establishing the “Rules of Analysis.” In the early stages of the trial, you must show the jurors the correct standard of medical and scientific analysis, and then proceed to show how the defense expert failed to follow this correct standard.

When you deal with issues of liability, the process is clear: establish the accepted rules, show the jury how the defendant failed to follow these rules, and establish that it injured your client. These rules might be found in state statutes, codes, regulations, standards, rules of the road, or other acceptable “common sense” rules.

However, when you deal with the defense’s medical or technical expert, you have to teach the jury the “Rules of Analysis.” These expert opinions are based on medical or scientific analysis, a.k.a. the tried and true, accepted methods our doctors and experts use.

It is important to have an expert on your side who can explain these Rules of Analysis as basic principles of science and medicine taught to all medical students (and followed by all physicians). During direct examination, your expert should explain the step-by-step process of analysis that is required to come to an accurate conclusion.

Whether it’s something simple, like teaching the jurors about a differential diagnosis, or something complicated, like evaluating the proximate cause of the biomechanisms involved in a brain injury, your only reliable tool for undermining a defense expert is to show how he or she violated certain required steps in arriving at the final conclusion. In other words, you must show that:

  • The defense expert did not do his or her required job
  • The defense expert’s intentional failure or skipping steps was necessary to arrive at the final opinion
  • Therefore, the defense expert’s opinion is not reliable

Once you do this, you have impaired the foundation of your expert’s opinion, which impairs the expert’s credibility and impairs the credibility of the defense as a whole. The jurors will not look favorably on the defense’s attempt to be deceptive or deliberately withhold information; using this anger, the jurors will often respond with a more favorable verdict than you otherwise expected. These Rules of Analysis and the emphasis on the defense’s flawed science will make sense to your jurors and help your case in a major way.