Your client is a rational, mature businessperson. You expect them to do well at their upcoming deposition. After all, they have plenty of real-world experience, and of course, you go over the facts of the case with them as well as some deposition basics. You are subsequently horrified when they waffle, or get angry, or are evasive, or volunteer or do any of the multitude of the other communication sins that constitute poor testimony.
But here’s the thing. Whether your witness is a CEO or a homemaker, he or she must be prepared as rigorously for deposition as if they were going to trial. Even though, these days, trial is highly unlikely. Why? Because trial or no trial, depositions are critical to your effectiveness in negotiating the best possible settlement for your client. Yet time after time, lawyers fail to prepare witnesses sufficiently for deposition. The reasons are simple. Too much to do, too little time.
Here's a tip. Tell your witness that although it may seem like he/she is responding to opposing counsel’s questions, in truth, the witness is addressing the jurors. It doesn’t matter whether or not the matter ever gets to trial, when the witness responds as if he/she is speaking to jurors - being informative rather than defensive, polite and even-tempered despite opposing counsel’s ploys - the quality of testimony improves dramatically, and with that, far greater chances of your (and their!) success.