For your expert witnesses under the gun of cross-examination, usually the most problematic answer is a flat “yes” or “no.” Science holds few absolutes to be true, thus most scientists (which is the majority of your experts) are uncomfortable with an uncategorical “yes” or “no” in response to many of opposing counsel’s questions.
Yet opposing counsel has one goal in mind: get that expert to say “yes” to certain questions and “no” to certain others.
A useful technique is to suggest to your expert that he/she respond with a qualifier in front of their “yes” or “no,” such as: “In this situation, yes.” “Under certain conditions, no.” “When X is detected, yes.” “In the presence of Y, no.” And so on.
These responses open the door to asking your witness later, why he/she qualified their answer in such a manner.
Now, here’s where it gets really interesting: the results of meta-research on 107 different studies conducted over 50 years on persuasion and sidedness* show that two-sided arguments are more persuasive than their one-sided equivalents, as long as counter-arguments are raised when presenting the opposing view.
So, in telling the jury the rationale behind the qualifier, the expert can present his/her thinking as, for example; “It could be said, as opposing counsel’s expert stated, that …, however, studies show that …, which is why my opinon is …” which format serves to present the two sides of the argument, and raises the counter argument.
According to the meta-research, not only is such an approach more convincing, it also boosts the speaker’s credibility.
*Daniel O’Keefe, 1999, Communication Yearbook, 22, pp. 209-249