By Dr. Ken Broda-Bahm:
Testifying in deposition and on cross-examination can seem like a battle for control. Opposing counsel is aiming to fit the witness into a script, and the witnesses (hopefully) are trying to speak for themselves. A well-prepared witness will have a lot of tools at their disposal in aiming to at least come out even in that battle. But here is one of the major tools, and frustratingly, it is the one that I seem to have the greatest trouble trying to get witnesses to consistently use: a full sentence answer. That means a subject, a verb, and an object; an answer that is complete in its own right and doesn't depend on the question for clarity and context. In the hands of a well-prepared witness, the technique of generally answering with a full sentence stands the best chance of protecting the witness and the record over the long haul of testimony. But witnesses, and sometimes their attorneys, will often resist.
For the attorney, it can be a matter of preferring simplicity: "If the answer is yes, then just say 'yes.'" Less complexity, fewer words to deal with, less chance for a slip -- it feels like the attorney has greater control. But broadly speaking, simplicity and control aren't the goals of good testimony. Rather, the goal is to present the full, fair, and complete truth, and to do so in a light that is most favorable to your side in an adversarial proceeding. That doesn't mean rambling or going beyond the scope of the question. But it does mean making sure that you, and not counsel, are setting the terms and laying out the testimony. For most questions, that means more than saying "yes" or "no." In this post, I'll share my best list of reasons why a full sentence answer will generally serve a witness better than the "safe and simple" yes/no route.