How to Give Expert Testimony: What New Experts Need to Know When Testifying at Trial

One of the key roles of an expert in legal cases is testifying in court. As a newer expert, you will want to develop your effectiveness at giving expert testimony.

Carolyn Casey, J.D.

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— Updated on June 22, 2022

How to Give Expert Testimony: What New Experts Need to Know When Testifying at Trial

There are a few guidelines to learn about the mechanics of delivering your expertise in a courtroom setting. Following these tips will also help you present yourself as a credible authority to the jury during your expert testimony.

Questions About Your Profession

Often cases involve complex topics that are not easy for layperson juries to get their head around. As the trier of facts, they must understand all facts including those of a technical nature.

Your role is to explain complex topics that you understand as a professional to a jury. A lawyer brings you on board because of your specialized knowledge of an issue in their case. In discussions with the lawyer, ask what the technical issue is that they want you to testify on at trial. Confirm your knowledge, professional experience, and credentials in your conversations.

An understanding of the subject matter and required credentials will help when opposing counsel asks about your profession and qualifications. It is standard practice for the opposition to probe you on your profession and experience. Don’t let it rattle you. Simply answer the questions—you know you have the expertise, so tell them about it.

Stick to the Facts During Your Expert Testimony

Your role as a subject matter expert is to provide clarity on the facts of the case. You’re there to help the jury understand a topic that is complicated and technical.

It’s important to avoid straying into implying or stating a legal conclusion. This is not the expert’s job.

A contested will and the issue of the mental capacity of the person who executed a will are instructive on the line between factual opinions and legal conclusions. A qualified medical expert can testify on the will’s author’s mental capacity to understand the nature of their property. Then, they can formulate a plan for how they want it distributed. However, an expert stating that the person “had the capacity to make a will” would be a forbidden legal conclusion.

Preparing for Cross-Examination

Opposing counsel will ask you questions aimed at discrediting you and your testimony. This is the whole point of cross-examination. The opposition is trying to poke holes in your opinions. By doing so, the opposing counsel raises doubt in the jury’s mind about what you said. The opposing lawyer may also try to get you to say things that contradict your testimony. The opposition may also bring out information that undermines your qualification to testify.

First, take time to prepare. Study the opposition’s experts’ depositions and any testimony. Understand their point of view, methods, and conclusions. Review and refresh your memory on your own analysis or reports. If there’s a lag of time between when you testify and the cross-examination, review your own testimony too.

With this done, you will be able to respond accurately to questions on your analysis and testimony. If the opposing lawyer brings up something you said in a deposition or testimony, you won’t be caught off guard. You’ll know the context of your prior statements. When challenged, stay calm and speak firmly as you explain your reasoning and opinion. Convey your authority, but don’t come off as condescending. The jury is watching and listening. Hints of you talking down to the lawyer in your answers might cast you in a negative light. The jury might unconsciously turn against you or start to disregard your testimony.

Understanding the opposition’s point of view and expert opinions can help you anticipate cross-examination questions. When asked, succinctly state why you disagree with the opinions. Explain your view in a non-combative tone.

Keep Things Simple in Your Expert Testimony

When you are an expert, you have built up a body of knowledge and insight in a certain area. You have years or even decades of professional study and discussion of the topic with similarly trained professionals. You have a language and shorthand way of conveying information to those “in the know,” to your colleagues and network.

When you testify, it’s best to assume the jury is unfamiliar with the technical topic in your expert testimony. Lay some groundwork for them with the basics on the subject. Define any terms as you use them so it’s easy for laypeople to follow you and understand your testimony. Simplify complexity by breaking concepts down into smaller parts that are easier for the jury to absorb. The last thing you want is to lose their attention or leave them in a confused fog during your expert testimony.

Dress Code

There’s no need to be a fashionista to choose your attire for your expert testimony. But how you dress does require thought as it can affect how you and your expert testimony are perceived.

Overall, a good rule of thumb is to dress as you do while working in your profession. Balance overdressing with underdressing.

If you are a doctor, you might wear what you normally wear when you see patients in your office. If you are a professor, consider wearing what you wear when presenting a paper at a conference.

You usually can’t go wrong with wearing a suit if you are in doubt. This will convey your professionalism and respect for the proceedings. Business casual is also often perfectly acceptable. But remember to always wear closed-toe shoes.

Be Aware of Your Body Language

How you testify is as important as what you say as an expert witness. Aggressive gestures or an overly loud voice can shut juries down from listening to you. Keep eye contact for a few seconds with a juror or two as you speak to develop trust. In cross-examination, a jury will be aware of you crossing your arms in a defensive posture. This body language may make them think you aren’t telling the truth or that you are unreasonable.

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