Although in the “real world” scientists changing their minds may be the badge of intellectual honesty, in litigation the expert who backs away from a position or changes an opinion is supplying the opposition with a source of impeachment. Any time the expert makes a written record of his or her thoughts or opinions, the opposition gets a “paper trail” of potential impeachment material. To avoid this, tell your expert to keep writing to a minimum.
Whenever you have retained an expert witness to testify in your case—whether in deposition or at trial—you need to prepare yourself and the expert. Don’t just sit back and assume that the expert, who many have testified many times before, has it all worked out. You need to be up to speed on his or her testimony and to make sure the expert has enough information to be effective.