In Product Experience or Expert Experience?, patents expert witness James G. Rice writes:
Because patent litigation is one of the more complex areas of litigation, the expert witness is susceptible to making a critical mistake, for example, during a deposition. From my own experience, it appears that patent litigation is the foremost area of litigation in which technical issues can be strongly interwoven with legal issues. This can lead to the situation during a deposition where what may appear on the surface to be a relatively straight forward technical question can have critical underlying legal implications. I recall being asked during a deposition if a particular element of a claim was a “method.” The wording of the claim was not entirely clear on this issue and a less experienced witness might have simply answered “yes” and thus inadvertently have testified in effect that the claim was invalid. Although the attorney the expert is working with during preparation for the deposition may be excellent, it is difficult, if not almost impossible, to anticipate all of the avenues the opposing attorney may take during the course of a deposition. This makes it all the more important that the expert have strong experience in patent litigation.