Drafting Expert Witness Reports: Pitfalls and Best Practices

Expert reports can make or break a case. Mistakes in an expert report could preclude the expert from testifying; while a clear and comprehensive expert report could tip the scales in litigation.

Drafting Expert Witness Reports: Pitfalls and Best Practices

ByJoseph B. Evans, J.D.


Published on January 31, 2017


Updated onSeptember 7, 2022

Drafting Expert Witness Reports: Pitfalls and Best Practices

Experts and attorneys should be aware of what is required and should also take note of the tips and potential pitfalls related to drafting and submitting expert reports.

Required Information

The first step is making sure that the expert report includes all that is required. Failing to comply with these requirements runs the risk of excluding expert testimony altogether. While the rules vary from state to state, at least 35 states have adopted procedural codes based loosely on the Federal Rules. Federal Rule of Civil Procedure 26(a)(2)(B)(i)-(vi) governs the requirements for expert reports in civil cases:

(i) a complete statement of all opinions the witness will express and the basis and reasons for them (ii) the facts or data considered by the witness in forming them (iii) any exhibits that will be used to summarize or support them (iv) the witness’s qualifications, including a list of all publications authored in the previous 10 years (v) a list of all other cases in which, during the previous 4 years, the witness testified as an expert at trial or by deposition (vi) a statement of the compensation to be paid for the study and testimony in the case

Federal Criminal Rule of Procedure 16(a)(1)(G), (b)(1)(C) outlines the expert witness disclosure requirements in criminal cases. There are corresponding provisions for the government (16(a)(1)(G)) and the defendant (16(b)(1)(C)) which require the expert to provide a “written summary of any testimony” which includes the “witness’s opinions, the bases and reasons for those opinions, and the witness’s qualifications.”

Tips For Effective and Defensible Expert Reports

There are certain habits that, while not technically required, are suggested best practices when drafting expert reports.

Before drafting a report, experts should discuss the scope of the report with the attorney in detail. Some attorneys desire narrowly tailored 3-15 page reports, while others may want 100s of pages depending on the issues and client. Skipping this critical step can cause unnecessary work and expense.

Also, keep in mind that any documents reviewed by an expert must be recorded. It is most efficient to log these documents as the expert goes through the material by keeping a record of the document by title, date, length, bates stamp, and/or exhibit letter as applicable. Relatedly, it is also helpful to include a bibliography listing the relevant authorities and research reports upon which the expert relied on in forming the opinion and attaching those sources to the report as an appendix.

Ultimately, the report should be easy to read and look professional. It is a best practice to have a copy editor proof the report for spelling, grammar, and overall clarity. The expert should attempt to write for an intelligent lay audience by minimizing jargon and abbreviations where possible and thoroughly defining jargon and terms where necessary. Here are some basic drafting tips to consider when writing an expert report:

• Using your professional letterhead • Using 12-point font and 1½ line spacing • Creating topic headings and short, concise paragraphs • Providing a unique number for each page, table, chart, and exhibit • Including a cover page and table of contents • Indicating when and by whom your report was requested • Including the date you received the documents and formed your opinion • Stating that you may have additional opinions or updated/revised opinions if new information/documents are provided • Defining technical language and explaining any abbreviations • Including a summary of your conclusions/opinions

Things To Avoid At All Costs

The failure to provide timely and comprehensive expert reports can have disastrous consequences. The expert report needs to be sufficiently comprehensive to establish admissibility under all of the Rule 702 criteria. Failure to do so could result in barring the testimony of the expert witness.

The author of an expert report must be particularly careful about the facts he cites as a basis for his conclusions. Experts have been barred from testifying because of misstatements or faulty assumptions contained in their expert reports. In a case in which a deceased shipyard worker sued a paint manufacturer for his exposure to paints and paint thinners the plaintiff retained an expert doctor to testify to the plaintiff’s “cumulative benzene exposure while using [the paint manufacturer’s] products.” While affirming the ruling that precluded that expert from testifying, the Fifth Circuit wrote “a few scattered errors in an expert report are not necessarily grounds for exclusion . . . [h]ere, however, the universe of facts assumed by the expert differs frequently and substantially from the undisputed record evidence.”

Experts and attorneys should also be acutely aware of deadlines and the required detail. In one instance, an expert was barred from testifying entirely after the plaintiff provided the expert’s name and resume on the deadline set by the Court, to be followed later with a one-page “preliminary report”. The Court barred the expert from testifying because “the plaintiff was just way late in naming an expert” and “the expert witness’ report is pretty much a brief of legal conclusions in the case, and I don’t think it is something that offers expert opinions on the issues on which an expert might be allowed to testify in this case”. The Fourth Circuit upheld the decision.

In a securities fraud criminal prosecution, a number of brokerage firm employees were indicted for providing confidential information to outside traders. The government alleged that they were engaged in a “front-running” scheme. The allegations were that the brokerage employees and outside traders were making illicit gains by tipping off outside traders about large client orders so that the outside traders would be able to trade ahead of the large client orders.

At trial, a defendant attempted to call an expert to testify about the “mechanics of trading on the New York Stock Exchange” and “the meanings of relevant terms, concepts and practices within the securities industry, including but not limited to, day trading, trading volume, order flow, institutional trading, short selling, wash sales, and front-running” as well as the purpose of “squawk boxes.”

The Court excluded the expert from testifying because the defendant submitted the expert report on the day of trial, and not ten days prior as ordered by the Court. The Court also noted that the proposed testimony of the expert would have been excluded anyway since the report failed to provide “scientific, technical, or other specialized knowledge [which] will assist the trier of fact to understand the evidence or to determine a fact in issue.” United States v. Mahaffy, No. 05-cr-613, 2007 U.S. Dist. LEXIS 30077 (E.D.N.Y. Apr. 24, 2007) (this conviction was later overturned by the Second Circuit on other grounds).

Other criminal cases have held that “merely identifying the general topics about which the expert will testify is insufficient; rather, the summary must reveal the expert’s actual opinions.” And “providing the government with a list of sources from which the experts drew their opinions” but “not specify[ing] which sources the expert used to reach the different opinions identified” is insufficient. Experts must take special care in drafting their reports in criminal cases. Although the requirements of the Rules are not as spelled out as their civil counterparts, the Courts have held expert reports to an exacting standard.

Although not specifically barred by the rules, below are some things that experts are cautioned against using in their reports:

• Absolute wording and phrasing • Terminology such as “including, but not limited to,” and “relevant portions of” • Hedge words or phrases such as “sort of,” “somewhat,” or “I suppose” • Argumentative language • Comments on the credibility of other witnesses • An informal or overly friendly tone • Opinions outside your expertise or on issues(s) you were not asked by the attorneys to address • Superlatives like “very” or “extremely,” unless they are clearly warranted

There is a delicate balance when it comes to the appropriate degree of attorney involvement in expert report production. As Nigel Kent writes: “Legal counsel not only can but, from a practical point of view, must assist the expert in the preparation of any report to be used as evidence in the lawsuit.” Attorneys must provide their expert with the scope of the inquiry, the requirements of the report, and the factual background of the case. However, attorneys should not write the expert report. Although “attorneys are not precluded from assisting expert witnesses in the preparation of their reports so long as the witness remains substantially involved,” it can become a hotly litigated issue and opposing parties have argued that expert reports substantially drafted by an attorney should be barred from evidence, and the expert precluded from testifying at trial.

Properly drafting expert reports is of critical importance because the failure to do so could preclude the expert from testifying entirely. The expert should be confident that the report has satisfied all that is required and, perhaps most importantly, be comfortable with the findings within it because he or she will almost always have to defend the expert report under oath.

About the author

Joseph B. Evans, J.D.

Joseph B. Evans, J.D.

Joseph B. Evans, J.D., is a defense attorney who represents government officials and senior executives in high-profile white-collar criminal matters, regulatory matters, and commercial litigation.

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