To Impeach or Not to Impeach: That is the Question (Part Three)
In deciding whether to impeach an expert deponent, special considerations apply. Experts are in a much better position to fix impeachment than percipient witnesses are. If a percipient witness was not in a position to see whether the light was red or green, there is very little the percipient witness can do to fix this problem. But experts form opinions based on assumptions and factual conclusions they are given or arrive at through their analysis. Thus, a little further analysis after the deposition usually gives the expert a plausible path around the impeachment efforts.
Often, the most effective attack on experts is to challenge the assumptions they made or facts they relied upon from others, rather than taking on the expert’s opinion directly. In such cases, our examination will often begin with the same steps: locking down the expert as to what opinion she reached and the basis for that opinion. Now we either confront the expert with the relevant testimony or wait and do so at trial. If we do so immediately, a good expert will admit that he did not consider the fact, will give a reason why it probably does not affect his opinions, but will also state that he will want to consider this fact after. At trial, he will say he considered the fact and will have the best possible explanation for why the fact is unimportant.
Therefore, in most cases with an expert, we are better off saving the impeachment. But, note, this is risky. If we’re not sure how the expert will explain his position once he is confronted with the testimony at trial, we do not know whether we will want to engage in that exchange.
And, finally, saving impeachment for trial only makes sense where the impeachment material and position can remain hidden. If you have an expert on your side who issues an expert report criticizing the opposing expert for failing to take these facts into consideration, waiting makes no sense. Run the issue to ground in the deposition.
