Defense counsel must be alert for circumstances in which an expert can be of use. Experts can be used in a variety of capacities. For example, medical experts can establish the time of death or the height of the individual inflicting a wound. Psychiatrists can establish insanity or diminished capacity.
- An expert may be used only in an advisory capacity to assist in formulating a defense. The advisory expert then would not testify at trial.
- Bring the testifying expert into the case at an early stage, so that the expert is not hindered by the passage of time and/or destruction of important evidence.
Counsel should give careful consideration to the selection of an expert. Consider the expert's stature in his field, availability, and costs for services. Try not to use an expert who derives most of his income from testifying at trials, the so-called "professional expert."
While an expert with a sound formal education, and practical experience and scholarly publications is important, it is also important to select an expert who communicates well and can "connect" with a jury.
- Fully explain your tentative theory of defense to the expert and what you hope to prove through the expert.
- Ask the expert for his opinion about how best to present the defense.
- consulting one expert, an additional expert may be needed.
The defense expert at trial
- Must be calm.
- Must understand the rules of evidence.
- Must be well-prepared for direct testimony and cross-examination.
- Must give responsive answers.