When legal cases go to trial, most of the evidence that comes before the judge and jury is provided by witnesses. However, the rules of evidence do not treat all witnesses the same way.
One of the most important distinctions in a trial is the distinction between fact witnesses and expert witnesses. This is a difference that can become muddled in some circumstances, but it’s important for attorneys to keep the difference straight. Here’s what you need to know.
Fact witnesses can only testify about their personal knowledge
A fact witness, also known as a general witness or lay witness, is someone with personal knowledge related to the case at hand. Fact witnesses can only testify about their personal knowledge: what they saw and heard firsthand.
While it’s often claimed that fact witnesses cannot offer opinions, the reality is a little more nuanced (and varies by jurisdiction). Under Federal Rules of Evidence 701, lay witnesses can offer opinions as long as those opinions are rationally based on the witness’s perception, helpful to clearly understand the witness’s testimony or determine a fact in issue, and not based on scientific, technical, or other specialized knowledge. For example, a lay witness can testify that someone seemed anxious, in the layman’s sense of the term, but they can’t offer an opinion on an anxiety disorder without being qualified as an expert.
Expert witnesses can testify about their professional opinions based on specialized knowledge
An expert witness is someone with scientific, technical, or other specialized knowledge who can help the fact-finder understand the evidence. Many expert witnesses, including medical expert witnesses, have advanced degrees and formal training in a particular subject. However, anyone with “specialized knowledge” can theoretically be qualified as an expert in something, whether they acquired that knowledge through formal education or another source.
Unlike lay witnesses, expert witnesses are allowed to offer opinions based on their specialized knowledge as applied to the facts of the case. Because expert testimony can be so powerful, the courts put significant guardrails on expert witnesses’ qualifications. At the federal level, those guardrails were articulated by the Supreme Court in Daubert v. Merrell Dow Pharmaceuticals and Kumho Tire Co. v. Carmichael and codified in the current version of Rule 702. To qualify a witness as an expert, the court must determine it is more likely than not that:
- The expert’s scientific, technical, or other specialized knowledge will help the trier of fact to understand the evidence or determine a fact in issue;
- The testimony is based on sufficient facts or data;
- The testimony is the product of reliable principles and methods; and
- The expert’s opinion reflects a reliable application of the principles and methods to the facts of the case.
Most states have similar requirements for expert witnesses, although again, the rules vary from state to state.
The line between fact witnesses and expert witnesses can be blurry at times
Some types of cases involve multiple witnesses who have scientific, technical, or other specialized knowledge, not all of whom may be formally qualified as experts. In medical malpractice cases, for example, many of the fact witnesses (including the defendant) are medical professionals with specialized training and experience. Those fact witnesses may not be asked for expert opinions, but they may be asked questions about their medical decision-making or other facts that involve their medical knowledge. Often, plaintiff and defense lawyers will disagree on whether a particular question calls for an expert opinion or merely the witness’s personal knowledge.
Having the right expert witness can make all the difference
Because expert witnesses have the unique ability to provide opinions based on their specialized knowledge and analysis of the evidence, their testimony can carry a great deal of weight in the eyes of the jury. That’s why it’s so important to have highly qualified and highly credible experts in support of your case. Since 1986, the team at Rieback Medical-Legal Consultants has been providing top-notch medical experts to assist with the many levels of legal cases that require medical expert testimony.
If you need an expert for a potential or current case, give us a call or contact us online today. Our office is located in Fort Lauderdale, FL, and we offer our services to attorneys nationwide.