An Overview of Opinion and Expert Testimony
Article VII (FRE 700 Series), otherwise known as the Opinion and Expert Testimony rules, provides guidance for the admissibility of a witnesses opinion and conclusions during their testimony.
A simple explanation and a reason why these rules exist is so that the court can tell the difference between bias and opinion from facts. Therefore, these rules lay out what is acceptable as testimony from lay (everyday people) and expert witnesses.
This article will go over the 5 rules that are laid out as:
- Rule 701. Opinion Testimony by Lay Witnesses
- Rule 702. Testimony by Expert Witnesses
- Rule 703. Bases of an Expert’s Opinion Testimony
- Rule 704. Opinion on Ultimate Issue
- Rule 705. Disclosing the Facts or Data Underlying an Expert Opinion
Lay vs Expert. What’s the difference?
A witness can fall into two categories: lay or expert. Therefore, it’s good to know the differences between them.
- A lay witness is your everyday person who is testifying the facts of what occurred, and not what they believe as an expert. For example, a lay witness can simply be the one who witnessed the crime of a bank robbery or the one who witnessed the victim falling inside a convenience store.
- An expert witness is one that is qualified by a particular trait such as knowledge, skill, experience, training, or education and one that relies on scientific, technical, or specialized knowledge. They are allowed to infer what they believe using this knowledge and associated evidence when they are testified during trial. For example, a civil engineer can be entered in as an expert witness and can use research or domain knowledge to infer that a stop light was unsafe at a particular intersection.
Rule 701: Opinion Testimony by Lay Witness
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These rules allow certain opinions made by a lay witness to be heard. It explicitly defines what a lay witness is allowed to admit during testimony. However, in order for the testimony to be admitted, it must pass all three rules. The rules are:
- The witness must perceive these opinions out of their own senses (i.e., They came up with the conclusion using their senses)
- The witnesses opinion must advance the case or provide clarity to the case
- The witnesses opinion CANNOT include scientific or specialized knowledge.
If it passes all three rules, the opinion is allowed under Rule 701.
Rule 702: Testimony by Expert Witnesses
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These rules allow opinion testimony by a witness who is qualified to answer under their expert knowledge, skill, experience, training, or education. If they are not an expert in the specified field, they are not allowed to make opinion testimony under the subject.
In order for opinion testimony for an expert witness can be entered, it must pass the following tests:
- The witness must be an expert in their admitted field (i.e., A witness must be an expert in their field(s) before they can answer the question)
- The testimony must advance the case or provide clarity
These tests only apply to Mock Trial. In the real world, it must pass a few additional tests concerning the validity of the facts and data.
Rule 703: Bases of an Expert’s Opinion Testimony
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In Mock Trial, Rule 703 is a continuation of Rule 702. Specifically, Rule 702 answers “can the person give an opinion?”. Rule 703 answers “can the person tell you why they can give an opinion?”
These rules allow opinion testimony by an admitted expert witness. The rule states that the expert witness must form their opinion from facts or data within the scope of their knowledge. To further define:
An expert witness may form an opinion from facts or data from these sources:
- Personal Observation (field of work)
- Information at Trial
- Other Sources (academic papers not cited by the expert, interviews)
For example, an expert witness that is entered as an expert in mechanical engineering can form opinions based on their personal experience as a mechanical engineer, information that was presented during trial, and third-party academic papers or interviews.
Rule 704: Opinion on Ultimate Issue
This rule is often misunderstood and confused. There are different rules for different types of cases. We will break it down into what to do for a civil case and a criminal case.
Ultimate Issue – The question(s) the jury has to answer based on what they’ve heard or seen in trial.
In both civil and criminal cases, an attorney cannot object when a witness is asked to testify about the ultimate issue.
What to do in a Civil Case when it comes to Ultimate Issue
- Nothing. An opinion about the Ultimate Issue is not objectionable.
What to do in a Criminal Case when it comes to Ultimate Issue
- An expert witness cannot make an opinions about the motive regarding the ultimate issue
- For example, the expert witness cannot say “In my expert opinion, the defendant had the motive/mindset/intent to commit the crime.” This is objectionable.
Rule 705: Disclosing the Facts or Data Underlying an Expert Opinion
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This rule basically states that an expert may state an opinion without having to disclose the facts or data.
However, if the expert witness does make an opinion and they are asked to disclose the facts or data, they have to disclose it. This will typically occur during cross examination where the opposing counsel may ask to clarify their opinions using facts and data.