What to Include in an Expert Rebuttal Report

Serving as an expert witness during a lawsuit often extends beyond writing an initial report or giving testimony at deposition or trial. Expert witnesses may also be asked to evaluate the reports generated by an opposing party’s expert witness and to raise issues they find in that report. The resulting document is known as a rebuttal report.

Dani Alexis Ryskamp, J.D.

Written by
— Updated on August 17, 2022

What to Include in an Expert Rebuttal Report

What is a Rebuttal Report?

A rebuttal report analyzes and refutes the positions the opposing expert takes in their expert witness report. A good rebuttal report will establish a foundation for questioning the expert’s credibility. Through this foundation developed and the analysis presented, the strongest rebuttal reports also demonstrate that the rebutting author took the best route available for understanding the issues in the case.

When a rebuttal report does double duty in this way, it not only exposes weaknesses in the opposing expert’s conclusions but also reaffirms the strength of the conclusions reached by the rebuttal’s writer in their own expert witness report.

Read, Then Rebut

The first step in any strong rebuttal is to thoroughly understand the arguments, methods, and conclusions presented by the opposing party.

Start by reading the report to familiarize yourself with its layout, contents, and conclusions. Then, reread it, focusing on areas of weakness within the methods, analysis, and conclusions. Many expert witnesses perform this step with a pen or highlighter handy so that they can make notes for themselves.

While reading critically, also note any places where the opposing expert’s report agrees with your own work or with the position taken on the side of the case to which you are contributing. Identifying areas of agreement can help you focus the rebuttal on the areas of disagreement. Establishing agreement can also help build your own credibility as a rebuttal source because it demonstrates that you are able to acknowledge similarities rather than merely reacting from bias.

Moving Beyond the Report

Once a clear understanding of the opposing expert’s assumptions, methods, analysis, and conclusions has been established, it may help to attempt to recreate the opposing expert’s analysis. Such a recreation can reveal specific flaws in the expert’s approach. It can also reveal how that flawed approach led to flawed conclusions.

Not all cases will lend themselves to a recreation of an opposing expert’s analysis. Time and resources may be scarce, for example, or the opposing expert’s approach may depend on factors that can’t easily be recreated. In these cases, an expert may nevertheless benefit from walking through each step of the analysis, imagining how it would have been carried out in practice, and looking for flaws.

During this process, stay alert both for explicit assumptions and implicit assumptions. Explicit assumptions are typically stated outright—they’re known to the opposing expert and may be factored in as part of the conclusion. Implicit assumptions, however, may not be stated outright. in fact, the opposing expert may not even be aware of them but they nevertheless affect the conclusion.

Addressing both explicit and implicit assumptions can help an expert write a clearer rebuttal, especially if any assumption affects the conclusions reached.

Key Issues to Address in a Rebuttal Report

The rebuttal report should address a number of areas. First, as noted above, summarize the issues or topics on which your own work agrees with that of the opposing expert. Create common ground as a way to build credibility and direct the reader’s attention toward key areas of disagreement.

Identify any clear, objective errors, such as errors of fact or mistakes in calculation. Such errors do not appear in every expert witness report. But when they do, they provide a clear, easily-evaluated starting point for discussing weaknesses in the report.

Next, focus on any contradictions within the report. Contradictions and inconsistencies often indicate flaws in methodology, analysis, or resulting conclusions. Examples include inconsistent use of inputs, switching methodologies, or citing and quoting sources selectively or out of context.

As you identify issues, provide alternatives where possible. For example, if a mathematical equation was solved incorrectly, provide the correct solution, and explain how the correct solution affects the opposing expert’s conclusions. If the opposing expert quotes a source out of context, provide the context and explain its effects on the expert’s report and the case as a whole.

Finally, avoid contradicting your own work or the client’s position in your rebuttal report. Ideally, the rebuttal will serve as further evidence that your own work is correct and the client’s position is justified.

Rebuttal reports require experts to balance multiple perspectives at once. They also require experts to think critically about their own and an opposing position simultaneously. This exercise in critical thinking, done well, can have a profound effect on a client’s case.

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