Two Experts Who Disagree
Both sides instruct a specialist, both specialists are qualified, and the reports reach opposite conclusions. The decision-maker cannot evaluate the expertise, and so the question becomes which of the two analyses can be followed and tested.
The rule in short
Competing expert evidence is resolved on reasoning rather than on credentials, because reasoning is the part a decision-maker can actually evaluate. Where two reports differ, the disagreement almost always sits in the assumptions applied, the material examined or the method chosen, and identifying which of the three is responsible narrows an apparently unresolvable clash into a specific question that somebody can answer.
A decision-maker faced with two qualified people reaching opposite conclusions cannot resolve it by assessing expertise, because they do not have the expertise to do so. What they can assess is whether each analysis is followable and whether its inputs are sound.
Where the disagreement actually lives
Different assumptions. The most common source by a considerable margin, because each expert was given the facts by the party instructing them and those accounts differ.
Different material. One report may rest on documents the other never saw, which produces divergent conclusions without either analysis being defective.
Different method. Where a field offers more than one accepted approach, the choice between them may account for the whole difference in result.
Different questions. Instructions vary, and reports that appear to conflict sometimes answer subtly different questions and do not conflict at all.
Genuine professional disagreement. Real and less common than parties assume, and where it exists it should be identified as such rather than dressed up as one side being wrong.
Rarely about competence. Attacking the other expert's qualifications is the reflex and almost never the productive route, per who qualifies as an expert.
Narrowing the dispute
A joint statement. Experts directed to confer and produce a document setting out what they agree on and where they differ, which frequently reduces the dispute dramatically.
Agreement is usually broad. Two specialists in the same field agree about most things, and the joint statement makes that visible instead of leaving the impression of total conflict.
The reasons for disagreement are the point. A statement recording that the experts differ because one assumed X and the other assumed Y converts the dispute into a factual question.
Cross-application of assumptions. Asking each to state their conclusion on the other's assumptions shows whether the disagreement is about analysis or about inputs.
Written questions to each expert. Some forums permit questions in writing, which is a considerably cheaper way to test reasoning than examination at a hearing and produces answers on the record.
Compare the material lists first. Where one report rests on documents the other never saw, the fix is disclosure rather than argument, and it can be identified in minutes from the two reports.
Check whether the questions match. Instructions differ, and two reports that appear to conflict occasionally turn out to have answered different questions, which is set out in what an expert report must contain.
| Cause of divergence | How to detect it | How it resolves |
|---|---|---|
| Different assumptions | Compare stated assumptions | A factual finding |
| Different material | Compare material lists | Disclose and re-run |
| Different method | Compare described method | Expert evidence on method |
| Different questions | Compare instructions | Often no real conflict |
| Professional disagreement | Joint statement | Decision-maker chooses |
The single joint expert
One expert instructed by both sides. Used where a question is peripheral, technical and unlikely to be genuinely contested, and it removes the dispute rather than resolving it.
Instructions have to be agreed. Which is where the arrangement fails, because parties who cannot agree the question cannot use a joint expert productively.
It is not always appropriate. Where the question is central and genuinely contestable, a single expert deprives both sides of the ability to test the analysis.
Cost is the usual driver. Two reports plus hearing time to reconcile them frequently exceeds the value of the point in dispute.
Access to the expert is shared. Communications generally go to both parties, which changes how the relationship works compared with a party-instructed expert.
Directing experts to confer and record what they agree on is the single most effective step in a case with competing reports. It usually reveals broad agreement, isolates the actual point of difference, and does so before either party has spent a hearing day discovering the same thing in public.
How decision-makers actually choose
They follow the reasoning. The report whose route from material to conclusion is visible can be checked, and one that merely asserts a result cannot, per an opinion and a conclusion.
They test the assumptions against their findings. An opinion resting on a version of events the decision-maker rejects falls with it, whatever its technical quality.
They notice acknowledged limits. An expert who identifies what their material cannot establish reads as more reliable than one expressing everything with equal confidence.
They notice overreach. A conclusion stated more firmly than the method supports damages the whole report, including the parts that were sound.
They may accept neither. A decision-maker is entitled to reject both reports, or to accept part of each, and is not confined to choosing between them.
Presentation counts. Numbered paragraphs, attached working and consistent figures make a report usable, and usability is a real advantage in a contested case.
A practical approach
Read both reports against each other. Line up the material lists, the assumptions and the methods, and the source of the divergence is usually visible within an hour.
Concede the qualifications. Accepting that the other expert is competent costs nothing and makes every subsequent point more credible.
Aim at the inputs. The material examined and the assumptions applied are checkable facts, unlike the exercise of professional judgment.
Push for a joint statement early. The earlier experts confer, the more of the dispute disappears before anybody has spent money preparing to argue it.
Decide what a win looks like. Frequently the useful outcome is not defeating the other report but establishing that its conclusion depends on a fact still to be decided by somebody else.
Keep exclusion in reserve. Where a method genuinely fails rather than merely differing, the challenge is a different one, and the grounds are set out in when an opinion is excluded.
Competing expert reports look like a clash of authority and are usually a clash of inputs. Two qualified people given different assumptions and different material will reach different conclusions without either doing anything wrong.
The joint statement is the mechanism that exposes this. Experts directed to confer typically agree about most of the field and disagree about one identifiable thing, which is a far smaller problem than two opposed reports suggest.
Where a single expert can be jointly instructed, the dispute disappears rather than being resolved. It works for peripheral technical questions and works badly for central contested ones, and the distinction is worth drawing carefully.
Decision-makers resolve what remains on reasoning rather than on credentials, because reasoning is the part they can evaluate. The report that shows its route, states its limits and can be checked has a real advantage.
For anybody facing an opposing report, the productive sequence is to concede the expertise, line up the inputs, find the divergence and press for a joint statement. Attacking the other expert's qualifications is the reflex and rarely the answer.
Points to carry away
- Disagreements are usually about inputs, not expertise.
- A joint statement of agreed and disputed points narrows the argument.
- A single jointly instructed expert removes the dispute entirely.
- Decision-makers choose the report they can follow.
- Neither report has to be accepted in full.
Questions readers ask
Why do decision-makers not simply prefer the more qualified expert?
Because they usually cannot assess relative qualification in a technical field, and because the more qualified expert is not necessarily the more reliable one on this question. What a decision-maker can assess is whether an analysis is followable, whether its assumptions match the facts as found, and whether its conclusions are stated within what the method supports. A report that shows its route can be checked and partially adopted; a report that asserts a conclusion from an impressive curriculum vitae offers nothing to work with.
What is a joint statement and why does it help so much?
It is a document produced by the opposing experts after they confer, recording what they agree on and setting out each point of disagreement with the reason for it. It helps because two specialists in the same field almost always agree about most of it, and the impression created by two opposed reports is that they agree about nothing. Once the areas of agreement are recorded, the remaining dispute is usually narrow and frequently turns out to rest on a factual assumption rather than on expert judgment at all.
Can a decision-maker reject both expert reports?
Yes. There is no obligation to choose between the two, and a decision-maker may accept part of one report and part of another, or find that neither has established what it set out to establish. That possibility is worth remembering when framing a case, because it means the objective is not necessarily to defeat the opposing report. Establishing that its conclusion depends on an assumption the decision-maker is unlikely to accept achieves the same result more reliably.
Sources
- Federal Rules of Evidence — Rule 702, Testimony by Expert Witnesseslaw.cornell.edu
- Federal Rules of Civil Procedure — Rule 26, Duty to Discloselaw.cornell.edu
- Federal Rules of Evidence — Rule 706, Court-Appointed Expert Witnesseslaw.cornell.edu
- Federal Rules of Evidence — Rule 705, Disclosing the Facts Underlying an Expert's Opinionlaw.cornell.edu
- Federal Rules of Civil Procedure — Rule 16, Pretrial Conferenceslaw.cornell.edu
- Legal Information Institute — Expert Witnesslaw.cornell.edu
True Justice Record is a publication, not a law firm. This article states general rules and cites its sources; it is not advice about any particular case, and the law differs by state and changes over time.
More in Opinion That Counts as Evidence
Who Qualifies as an Expert
A witness may be qualified by knowledge, skill, experience, training or education, and any one of them suffices. The enquiry is whether this person knows something useful about this question, not whether they hold a particular qualification. A separate and prior question is whether the claimed field is one in which expertise genuinely exists.
Paying for an Opinion, and What It Buys
An expert is paid for time and analysis, and that arrangement is normal and disclosed. Fee structures tied to the outcome are treated differently and are prohibited in some fields. The questions that carry weight concern contingency, the proportion of a witness's work from one source, and the extent of instructing-party involvement in drafting.
What an Expert Report Must Contain
A usable expert report identifies the question it answers, lists the material examined, separates assumptions from findings, describes the method, shows the reasoning, states the qualifications relied on and carries the declarations the forum requires. Omissions are treated as weaknesses rather than as tidiness problems.