7 Tips to Ensure Your Expert’s Opinion is Admitted as Evidence

Successfully admitting expert testimony can be a game-changer in litigation, but it requires careful attention to legal standards and preparation. As a forensic accounting expert with experience in intellectual property infringement and other damages claims and rebuttal, I’ve seen how crucial these steps can be to ensuring the admissibility of expert opinions. Below are seven tips to strengthen your case—and legal grounds on which opposing counsel could move to disallow expert testimony if these tips are overlooked.

1. Understand the Admissibility Standards (Daubert & Frye)

Legal Risk: If the methodology used by your expert doesn’t meet the required standard, the court may deem the testimony inadmissible.  For example, see Waymo v Uber et al.

Under the Federal Rules of Evidence, particularly Rule 702 (expert witness testimony) federal courts and many states have adopted the so-called "Daubert Standard."  Under Daubert, an opposing party can argue that the methods used are not scientifically valid, are not based on sufficient data, or have not been subject to peer review. This standard tends to be strict in ensuring that the expert's methodology is sound and applicable. Please click here to learn more about the Daubert Standard.

Some states, including California (at least historically), instead follow the so-called "Frye Standard," a test which requires that the expert’s testimony be based on scientific methods that are “generally accepted” in the relevant field. Frye is seen as a more lenient standard than Daubert in some respects. Please click here to learn more about the Frye Standard.

2. Choose the Right Expert

Legal Risk: If your expert’s qualifications are insufficient, opposing counsel could challenge them under Federal Rule of Evidence 702 or an equivalent local statute. They may argue that the expert lacks the necessary education, experience, or training in the relevant field, thereby disqualifying their testimony. This point merits its own blog post, perhaps.

3. Establish Relevance Early-On

Legal Risk: Testimony must assist the trier of fact in understanding or determining a fact at issue. Under Federal Rule of Evidence 702(a), opposing counsel may argue that the expert’s testimony is irrelevant if it does not directly relate to the issues of the case or if it fails to address a matter outside the common understanding of a layperson. Ensure that the expert is clear on the scope of their deliverable, especially with respect to supplementary or rebuttal reports.

4. Thoroughly Vet Your Expert’s Methods

Legal Risk: As mentioned above, if the methodology your expert relies on is questionable, Daubert or other motions can be used to exclude testimony on the grounds that it lacks reliability or scientific validity. Opposing counsel may argue that the expert’s techniques are speculative or insufficiently tested, or that they fail to meet professional standards. Therefore, take measures to ensure your experts are complying with the standards you designate. I recommend you research recent and historic case law because outdated or discredited methodologies can lead to the exclusion of expert testimony under Daubert. Opposing counsel may argue that the expert relied on outdated science, recent case law rejecting the methodology, or new standards that call into question the validity of the expert’s approach.

5. Require a Detailed Expert Report (or Declaration)

Legal Risk: A weak or vague expert report is vulnerable to attack under Federal Rule of Civil Procedure 26(a)(2)(B), which requires a complete statement of all opinions and the basis for those opinions. Opposing counsel may file a motion to exclude testimony on the basis that the expert report is incomplete, unsupported by sufficient facts, or based on inadmissible information.

However, state laws differ. In California, experts are not required to prepare written reports as part of the discovery process in state court. This is in contrast to federal court, where Rule 26 of the Federal Rules of Civil Procedure mandates expert reports.

The relevant statute in California is California Code of Civil Procedure (CCP) § 2034.210-2034.310. Under this statute, parties are required to disclose the identity of expert witnesses they intend to call at trial, along with a declaration summarizing the expert’s qualifications, a general substance of their testimony, and the expert’s hourly and daily fees for services; there is no statutory requirement for a detailed written report like there is under federal law.

Instead, in California state court, the discovery process involving experts focuses on depositions. During expert depositions, attorneys can probe the substance of the expert's anticipated testimony and the basis for their opinions. This approach allows for expert discovery without a formal report requirement.

Thus, in California, if an attorney requests expert opinions or methodologies, many an expert may disclose them through declarations or testimony, rather than a written report.  That said, for a damages expert like myself who prepares complex calculations, I find I need to prepare, at minimum, report schedules/exhibits that set forth my calculations in order to testify about specific amounts and remind myself of the details.

6. Anticipate Challenges to Credibility & Prepare for Deposition and Trial Testimony

Legal Risk: Legal Risk: Inconsistent or poor testimony under cross-examination can damage an expert’s credibility, leading to a motion to strike the testimony as unreliable. Opposing counsel could file a motion under Federal Rule of Evidence 702(d), claiming that the expert has not reliably applied their methods to the facts of the case or challenging an expert’s credibility by pointing to prior inconsistent statements, or limited experience in the field. I suggest role playing with your expert to ensure they know how to respond to credibility attacks and your direct examination at minimum.

7. Emphasize Objectivity

Legal Risk: If your expert appears too aligned with your client’s case, they could be disqualified for appearing as an advocate rather than an independent professional. Opposing counsel may argue under Daubert or Federal Rule of Evidence 403 (which balances probative value against prejudice) that the expert’s bias renders their testimony unfairly prejudicial or untrustworthy.  As part of this, do not engage the expert on a contingent basis - if they have a financial stake in the outcome of the case, their testimony can be excluded. This is one reason why my firm bills hourly.

Conclusion

Hopefully some of these tips will help you overcome challenges to your expert. For information about Boschan Corp.'s expert services, please click here or call us at 424-248-8866.

Can a Lay Witness Offer an Expert Opinion?

Can a Lay Witness Offer an Expert Opinion? If you're a trial attorney, this question may come up more often than you'd expect, because introducing lay witnesses is one method of surprising the counterparty, since there are fewer disclosure requirements and procedures for lay witnesses than for expert witnesses in US federal and state legal proceedings.

As an expert witness (not an attorney) I find that the distinction between lay and expert witnesses is critical. Lay witnesses typically provide testimony based on their personal knowledge or observation, whereas expert witnesses are called upon to offer specialized knowledge that aids the court in understanding complex matters. However, the question often arises: can a lay witness ever give an opinion that might resemble expert testimony? The answer lies in a careful analysis of the rules of evidence and case law, which you should discuss with your legal counsel. The below represents my understanding as a non-lawyer, thus it should not be taken as legal advice.

The Role of Lay Witnesses

A lay witness is someone who testifies about facts they personally observed or experienced. According to Rule 701 of the Federal Rules of Evidence, a lay witness may offer an opinion, but only if it is:

Rationally based on their perception: The opinion must stem directly from the witness's personal observations and experiences, not from specialized or technical knowledge.

Helpful to understanding their testimony or determining a fact in issue: The opinion must assist the court or jury in grasping what the witness saw or experienced, providing clarity to otherwise factual testimony.

Not based on scientific, technical, or other specialized knowledge: If an opinion requires specialized knowledge, it falls under the domain of an expert witness, per Rule 702.

In other words, lay witnesses can offer opinions that are grounded in everyday reasoning and personal experience. For example, a lay witness may testify that someone appeared “nervous” or “angry” based on their demeanor, or that a vehicle seemed to be speeding. These observations are not considered expert opinions because they are accessible to any reasonable person without specialized training.

The Role of Expert Witnesses

An expert witness, on the other hand, is specifically qualified by knowledge, skill, experience, training, or education. Experts are called to offer testimony on subjects that require a deeper understanding beyond common experience, such as medical diagnoses, technical data, or financial calculations. Their testimony must adhere to the standards of Rule 702, which governs the admissibility of expert opinions.

The Gray Area: When Lay Testimony Resembles Expertise

There are situations where the line between lay and expert opinion blurs. In such instances, courts scrutinize the nature of the testimony to determine whether a lay witness’s opinion crosses into expert territory.

For example, in United States v. Figueroa-Lopez, a lay witness was prohibited from giving an opinion that the defendant was acting in the manner of an experienced drug trafficker. The court ruled that this opinion required specialized knowledge and, therefore, fell under the purview of expert testimony.

However, there are cases where lay testimony can approach expert-like opinions without crossing the line (i.e., when opinions are grounded in firsthand knowledge gained from practical experience, not formal expertise).

Practical Scenarios: When Lay Witnesses May Offer Opinion

• Eyewitness Accounts: A lay witness can offer opinions about the speed of a vehicle, the identity of a person they know, or the emotional state of someone they observed. These opinions are rooted in common sense and direct observation.
  
  
• Business Practices: Business owners or employees with firsthand knowledge of standard operating procedures can provide lay opinions about routine matters within their industry. For instance, a restaurant owner may testify about typical food preparation procedures without being considered an expert.
  
  
• Medical Conditions: A lay witness can testify about obvious, observable medical conditions (e.g., someone appeared to have difficulty breathing or seemed unconscious), but diagnosing a specific medical condition requires expert testimony from a medical professional.

Other Jurisdictions Differ, Including U.S. State Courts

Many US states have adopted rules that are similar or identical to the Federal Rules of Evidence, particularly Rule 701 (lay witness opinion testimony) and Rule 702 (expert witness testimony). However, states may interpret or apply these rules differently, leading to variations in what types of testimony are admissible in state courts.  For example,  New York has not formally adopted the FRE, but its courts follow a similar approach regarding lay and expert testimony. New York courts may allow a lay witness to offer opinions in certain situations where the witness has specialized knowledge from experience, but this remains limited. For instance, a New York lay witness might testify about common business practices in their industry without being formally qualified as an expert, as long as the opinion is based on personal experience and not technical or specialized knowledge.

Technically different states follow different standards for the admissibility of expert opinions, namely:

• The Daubert Standard: Under Daubert (adopted by federal courts and many states), the judge acts as a gatekeeper to ensure that expert testimony is scientifically reliable and relevant. This standard tends to be stricter in ensuring that the expert's methodology is sound and applicable.
  
  
• The Frye Standard: Some states, including California (at least historically), follow the Frye standard, which requires that the expert’s testimony be based on scientific methods that are “generally accepted” in the relevant field. Frye is often seen as a more lenient standard than Daubert in some respects.

Under California law, a lay witness may provide opinions that are rationally based on their perception and helpful to understanding the testimony or determining a fact. However, California courts may allow more flexibility in certain types of lay opinions, especially when it comes to areas like business practices or common knowledge.

The difference between Daubert and Frye standards primarily impacts expert testimony, but it also affects how strictly courts will distinguish between lay and expert opinions. A state following the Frye standard might allow lay opinions on subjects that Daubert jurisdictions would restrict to experts, depending on the situation.

Conclusion

While lay witnesses cannot offer expert opinions, they are permitted to provide certain types of opinion testimony based on their personal observations and experiences. The key is that their opinions must be rational, helpful to the trier of fact, and not based on specialized knowledge. This rule ensures that courts maintain the balance between reliable expert testimony and useful lay observations, all while upholding the integrity of the legal process.

Understanding the distinction between lay and expert testimony is vital in preparing for trial. Lawyers must ensure that lay witnesses stay within the bounds of what they are allowed to testify about, while also leveraging their observations effectively to support their case. As always, careful consideration of the rules of evidence will guide which opinions are admissible and which must be left to the experts.

When it comes to intellectual property infringement cases, having the right damages expert can make all the difference in a successful outcome. At my firm, Boschan Corp., we specialize in IP infringement damages and are here when you need a seasoned expert to support your case. As a trusted partner in forensic accounting, we’re ready to help. Visit our website: boschan.com for more information or call us today at (424) 248-8866 to clear conflicts and get started.