How to Craft an Effective Expert Witness Engagement Letter

Like any agreement, the relationship between an expert witness and the attorney and litigant should be memorialized in writing.

Anjelica Cappellino, J.D.

Written by
— Updated on August 27, 2021

How to Craft an Effective Expert Witness Engagement Letter


While engagement letters are thought to be less formal than a more contractual-looking retainer agreement, both documents share the same purpose: to outline the scope of the relationship with the expert. Becuase each expert-attorney relationship is unique, the specific requirements of the representation will differ from case to case. But generally, there are certain topics that all comprehensive engagement letters should include. By taking the time to draft a solid engagement letter at the outset of the relationship, unnecessary future complications can hopefully be avoided.

Establish the Kind of Expert You’ve Retained

Any solid engagement letter should define the services that the attorney expects the expert to perform. The first issue that should be decided is whether the expert is expected to testify. An expert witness’ duties and responsibilities are largely different from a consultative (or non-testifying) expert. Notably, a non-testifying expert’s identity is oftentimes protected, which allows for certain obvious advantages in terms of trial preparation.

Under Rule 26(b)(4)(D)(ii) of the Federal Rules of Civil Procedure, a party may not discover facts known or opinions held by an expert who is not expected to be called as a witness at trial except upon a showing of exceptional circumstances. Thus, consulting experts can investigate facts and issues of the case without disclosing their opinions opposing counsel. Contrarily, experts that do plan to testify need to disclose their findings accordingly. Pursuant to Rule 26, these experts need to provide a written report to opposing counsel which contains their opinions and the basis for them. Therefore, it is critical that the expert’s specific role and corresponding obligations are definitively stated in the engagement letter.

Define the Services to be Performed

Once an expert’s role is decided, a detailed breakdown of the expected work to be performed should be stated in writing. The type of work performed can vary as widely as the types of fields of expertise that exist. Depending upon their particular field of expertise, an expert’s services may involve reviewing voluminous documents, conducting experiments, and analyzing scientific methodologies. It is helpful for the letter to set forth a general timeframe of when the work is expected to be performed, and if necessary, the letter can also include deadlines.

In addition, if testifying at trial, there might be various exhibits and demonstrative aids that need to be prepared. With the advent of technology in the courtroom, these aids can be as simple as a PowerPoint presentation or as advanced as virtual or augmented reality programs. Anything that an expert is expected to prepare should be clearly stated for the sake of planning.

Clearly State the Expert’s Fees and Expenses

A breakdown of the expert’s fees and rates of compensation is a critical part of any engagement letter. Experts are compensated at vastly different rates depending on factors such as experience, training, expected work to be performed, and time requirements. Likewise, an expert’s rates for out-of-court work can differ from their rates for in-court testimony. If an expert charges per hour, opposed to a flat rate, the fee provision should specify any differentiations in hourly rates.

The engagement letter should also specify how expenses are handled. Typically, an expert’s expenses for printing, copying, mailing, materials, travel, mileage, lodging, and meals should be itemized. If necessary, the letter should state a timetable for when and how the expert should provide billing invoices to the attorney that must be paid subject to the time stated in the agreement.

Conduct a Conflicts Check

Prior to engaging an expert, a thorough vetting process should be conducted concerning the expert’s qualifications and potential conflicts of interest. Although courts infrequently disqualify experts on such grounds, a disqualification can have drastic consequences on a case. Therefore, it is critical to discuss any and all potential conflicts of interest with your expert, including whether their professional history could contradict or call into question their present work.

Conflicts of interest may occur if the expert was previously employed by (or testified on behalf of) the opposing party. Conflicts may also occur if the expert’s opinion directly contradicts their previous testimony. As such, any potential conflicts should be thoroughly investigated. While it might not be possible to predict all potential conflicts that may arise throughout the course of litigation, it is helpful for the engagement letter to specify that a conflicts check was conducted and that the expert is in a position to properly work on the case.

Include a Confidentiality Clause

An expert is a direct extension of the litigation team and as such, they are often exposed to an enormous amount of attorney-client privileged materials and confidential work product. Many times, an expert will possess these materials as well as part of their preparation. To protect these materials, an engagement letter should include a brief clause stating the confidential nature of the information and that upon termination of the relationship, the expert must return or destroy the items at issue. Likewise, the engagement letter should also state that all communications between the expert and the attorney (as well as the litigant and support staff) are confidential and should be treated accordingly.

Experts should also be made aware of the importance of their own communications. Almost all written communications of a testifying expert are discoverable under Rule 26 of the Federal Rules of Civil Procedure (as well as Rule 16 of the Federal Rules of Criminal Procedure) and many state courts have adopted similar disclosure obligations. An expert should be mindful of the written communications they produce, such as email correspondence and draft opinions. The engagement letter should note how and when the expert’s opinion should be rendered in order to avoid the unnecessary production of materials that could potentially tip off the adversary.

Don’t Forget a Termination Clause

Like any solid contract, an engagement letter should specify the timeframe of the relationship. In many cases, litigation can be ongoing with seemingly no end in sight. For a testifying expert, it may be difficult to state with certainty when their testimony would take place. But to the extent that a completion date can be defined, the engagement letter should so state. The letter should also list any justifiable reasons to terminate the relationship prior to the completion of litigation, such as the expert’s failure to perform the necessary services or the attorney’s failure to compensate the agreed upon amount. While many attorneys and experts work together seamlessly, it is possible for communications to break down. In such an event, it is important to have a thorough termination clause.

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