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c.
Knowing When to Say “I Don’t Know”
It is not an uncommon cross-examination strategy for an attorney to play
on every human being’s natural tendency to want to provide an answer to
every question. The best strategy to avoid being caught in this particular net
is to have firmly in mind the limits of both the evidence in the case and the
tests employed, as well as the limits of your own personal knowledge. Know-
ing when to say “I don’t know” is just as important as knowing the correct
answers to those questions for which they exist. Clever attorneys will evoke
a string of “I don’t knows” from a witness in an effort to convince those
listening that he isn’t the expert he claims to be. Regardless of how stupid
you are starting to feel, the correct answer is still “I don’t know” when you
don’t know.
 
d.
Yes or No
Most experts have, at one time or another, been confronted with opposing
counsel insisting that they limit their answer to “yes” or “no.” As we men-
tioned previously, the 
 
U.S. Federal
(and 
Uniform
) 
Rules of Evidence
explicitly
permit expert witnesses to explain their answers. Although many states follow
those guidelines, some jurisdictions may not. Either way, you may still find
an judge who will rule that you cannot explain your answer. A sometimes
effective rejoinder is to state that you cannot answer the question as asked
without misleading the jury. Other times it is best simply to pick the lesser
of the two evils and make sure that your attorney allows you to explain on
re-direct.
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