Insights
Consulting expert vs. testifying expert: when the distinction protects you
A consulting expert helps counsel understand a case. A testifying expert tells the finder of fact what they conclude. Treating the two as interchangeable — or converting one into the other partway through — is a decision with consequences that are easier to avoid than to unwind.
What each role is actually for
A consulting expert is engaged to advise counsel: to explain the technical landscape, identify what the records do and do not show, assess the other side's theory, and help frame the questions. A testifying expert is engaged to form and express an opinion that will be disclosed and tested.
The roles call for different things. A good consulting expert is candid to the point of bluntness about weaknesses, ranges freely over possibilities, and is useful precisely because they are thinking out loud. A good testifying expert is disciplined, states only what they can support, and is careful about anything that could be characterised as a prior inconsistent position.
Those are close to opposite working styles, which is one practical reason the same person is not always the right choice for both.
The extent to which each role's work receives protection from discovery differs by jurisdiction and by the rules of the forum, and it is a question for counsel rather than one this site answers.
Why the early conversation is best had with a consultant
Because the most valuable thing an expert can say early is that the records will not support the opinion counsel was hoping for — and that assessment is more freely given, and more freely received, outside a testifying posture.
This is the reason our own engagements put a verbal preliminary assessment before any written report. Counsel gets the candid read on what the records will bear while retaining control over whether a discoverable document comes into existence at all.
It also produces better strategy. An expert who knows they may have to defend every word tends to hedge; one advising counsel can say 'the imaging does not show what your client believes it shows' plainly, which is the sentence that changes the case.
Converting a consultant into a witness
It happens, and it is not automatically a problem — but it should be a considered decision rather than a drift. Everything the person has already said, written, and been shown becomes potentially relevant in a way it may not have been before.
The practical exposure is straightforward. A consultant who spent three months exploring theories, including ones later abandoned, has a history of positions. As a witness, that history is a resource for cross-examination in a way it was not before.
The safer pattern, where the budget allows, is to keep the roles separate from the outset: one expert helping counsel understand the case, another forming the opinion that will be served. Where a matter cannot support two, the decision to use one person in both roles should be made deliberately at the start, with the person told which role they are in.
How the applicable rules treat the conversion is a question for counsel and depends on the forum.
Where this intersects with disclosure
The three West Coast states use different disclosure mechanisms, and the one that matters most here is California's simultaneous exchange, which fixes the identity of testifying experts at a single moment for both sides.
Because neither side sees the other's disclosure first, there is no opportunity to select a testifying expert in response to the opposing designation. The decision about who testifies has to be made on your own assessment of the case.
That raises the value of the consulting stage. Where the testifying designation cannot be reactive, the analysis behind it has to be complete beforehand — and a consultant is the efficient way to get there without generating a disclosable position for every theory examined along the way.
Frequently Asked Questions
The protection given to consulting expert work differs by jurisdiction and by the rules of the forum, and whether it applies in a particular matter is a question for counsel. This site does not determine what is or is not discoverable.
Frequently, and in smaller matters it is often the only economic option. It should be a deliberate decision made at the outset rather than a drift, because a consultant who explored and abandoned theories has a history of positions that becomes available to cross-examination once they testify.
So counsel gets a candid read on what the records will actually support while retaining control over whether a discoverable document comes into existence. Where the materials do not support the theory, that is said during the assessment rather than after a report has been drafted.
It carries extra weight there because the simultaneous exchange means the testifying designation cannot be reactive — neither side sees the other's first. The analysis behind the designation therefore has to be complete beforehand.
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Preliminary screening is complimentary. Send the posture of your matter — jurisdiction, claims, and the schedule you are working under — and you will get a candid read on which expert discipline the issue points to and whether the materials look suitable for expert review. Serving attorneys and law firms throughout California, Washington, and Oregon — available for consultation, report preparation, deposition, and trial testimony, in person and remotely.
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