Your witness is being deposed. Maybe it's your client or your expert, but it's not going well. In fact, it's a disaster - a "technicolor nightmare" as one of my early supervising partners liked to say.
What do you do? Really, the question is what can you do.
The answer is not much.
Hopefully, this event is not a lesson in witness preparation, although it often is. Still, I have seen smart, well prepared witnesses turn into a "puddle of s***," as my old friend and former colleague, Coreen Silverman, has so graphically described a few clients and experts. (And there has never been anyone better at witness preparation than Coreen).
If you don't care about the rules and propriety, there are always speaking objections, aka witness coaching. Years ago, "aggressive deposition defense" was much more commonplace than it is now. It didn't work all that well even when you could get away with it. At best you might muddle the record a bit.
After the other side passes the witness, you can try to question him or her yourself in an effort to fix the problems. If someone has made a simple misstatement, that's one thing. Trying to repair hours worth of bad testimony is another one entirely.
In 38 years as a trial lawyer - most of it doing medical malpractice cases - I cannot think of a single deposition where such a clean up effort has been successful. In fact, as I have observed a couple of times recently, the effort by the defending attorney only made the problem worse - in one instance, a whole lot worse.
Almost always better to keep quiet and figure out how to try to repair your case later. Not that there is any guarantee you will be able to do so.
Preparing witnesses is one of the most important things you do as a trial lawyer. Do it right.
I could easily write the above a dozen more times - just for emphasis.
Finding yourself in the midst of a technicolor nightmare deposition is bad enough even when you've done everything you could do to get the witness ready.
If a deposition disaster is unfolding because the witness was not prepared appropriately, that's a very ugly, no fun, sinking feeling. (I'll take the 5th amendment as to whether I have ever had that sensation.)
And either way: Keep a poker face and don't whine.