Expert Witness “Side Switching”: What Happens and How to Respond

The credibility of an expert witness often relies on the belief that experts are, in a sense, neutral – even when they testify on behalf of one side or the other. Because experts are both evaluated on their approach to the facts and asked to testify about it, the perception of both the judge and jury is that the expert is ultimately on the “side” of facts, reason, and careful analysis.

Most experts believe this to be their role as well, and they do their work accordingly. Sometimes, this means that an expert will discover that their initial opinion was wrong if the facts, reasoning, or analysis support the opposite side.

No explicit rules prohibit an expert from switching sides or mandate that an expert do so. Questions that arise from the process are often dealt with in the moment, including the ultimate question: Whether the expert should be disqualified altogether.

Here, we look at some of the biggest questions raised by side-switching and provide guidelines for determining when to call for disqualification.

Switching Sides: What’s the Issue?

Even though experts are thought to be on the side of the truth, experts switching sides during a case can have onerous consequences. Some cases involving a “switched” expert result in the expert being disqualified, the attorney being sanctioned, or both. Others, however, continue without a hitch – and with the expert now testifying for the opposing side.

For courts addressing the question of side-switching expert witnesses, major questions typically include:

1. Confidentiality: What does the expert know, and what can the expert share with the opposing side? Federal Rule of Civil Procedure 26, which governs discovery, may be called into play, or its state court equivalents.
2. Credibility: Is the expert switching sides because he or she genuinely believes the other side is where the evidence leads – or because the other side just became the highest bidder? Since the power of an expert witness relies heavily on credibility, so do determinations of the proper response to a declared switch.
3. Outside Influences: In some cases, courts have dealt with the question of expert switching by dealing with an attorney who hired the expert away.

These considerations pose issues for expert witnesses as well. Regardless of the actual reasons for the switch or its outcomes, an expert who switches sides – or who is dropped from a case for announcing a change of opinion – risks public misperceptions that can damage his or her trustworthiness in future cases. Switching situations should be discussed carefully with the expert witness for this reason.

Disqualification: When the Correct Side is “No Side”

Courts have typically applied one of three standards to determine when the opposing party should have access to a “switched” expert:

1. “Exceptional circumstances:” The exceptional circumstances standard is based on Federal Rule of Civil Procedure 26(b)(4)(B), which protects certain disclosures (including expert witness reports) during discovery unless “exceptional circumstances” apply.
2. “Balancing:” This standard weighs the interests of the opposing party (whom the expert now supports) against the potential prejudice to the initial part (who first hired the expert).
3. “Entitlement:” A few cases have held that a party is entitled to call any expert that meets the standards for expert witness testimony, whether or not the other party opposes the decision.

The fact that you initially called this expert, however, does not automatically entitle the opposing party to recruit the expert – even if the expert’s opinion has switched.

For instance, imagine a situation in which the expert’s opinion switched from “your client is definitely correct” to “it’s impossible to tell whose position is correct.” Here, the opposing party will need to demonstrate that this theory is directly relevant to their side of the case, which can be difficult if their stance to date has been “our particular interpretation is correct.”

Likewise, an expert witness cannot be “picked up” by an opposing party in lieu of the opposing party securing its own expert witness. Both sides are expected to do their own work in consulting experts, not to sit around waiting for the other side’s expert to become available – or actively luring that expert away.

Therefore, it’s likely that a “switched” expert will simply be asked to step out of the case if:

1. No exceptional circumstances apply
2. The prejudice to your case outweighs the benefit to the opposing party’s case
3. The court doesn’t recognize entitlement
4. The expert’s new opinion is not directly relevant to the opposing party’s case
5. The opposing party has not acquired its own expert and is attempting to remedy this by acquiring yours

Since different jurisdictions use different versions of these rules, it’s important to ensure you know which apply to your situation in order to make the most effective arguments.