Medical Malpractice: Using Medical Expert Witnesses

Expert witness testimony is essential to most medical malpractice cases.

By , Attorney ● University of Michigan Law School
Updated by Stacy Barrett , Attorney ● UC Law San Francisco
Updated 12/28/2022

Medical malpractice claims are a type of personal injury claim with their own special rules and procedures. Unlike a person suing over a car accident or slip-and-fall, a medical malpractice plaintiff almost always has to hire an expert witness.

If you're thinking about filing a medical malpractice claim, here's what you need to know about using expert witnesses:

  • Medical malpractice experts are typically doctors, nurses, and other medical professionals whose training and experience qualify them to testify about a particular medical specialty.
  • They testify about the medical standard of care and the cause and seriousness of the plaintiff's injuries.
  • Medical experts interpret complex and technical medical information for insurance adjusters, lawyers, judges, and jurors.
  • Dozens of states require plaintiffs to get an expert opinion before they can even file a medical malpractice lawsuit.

Why Is Medical Expert Testimony Needed?

Medical malpractice plaintiffs typically have to prove four elements:

  • the plaintiff was under the care of the defendant
  • the defendant was negligent (provided sub-standard care)
  • the defendant's sub-standard care caused the plaintiff's injury, and
  • the plaintiff suffered specific types of harm as a result of the injury (damages).

A medical expert helps a plaintiff prove these elements. Most importantly, an expert is necessary to establish what the standard of care was under the circumstances and how the defendant failed to meet the standard. Only an expert can say that a medical professional failed to act with the skill and care that a similarly-trained professional would've shown under the circumstances. Expert testimony is also critical to proving that the doctor's sub-standard care caused the plaintiff's injuries.

Of course, defendants almost always hire their own experts to say that they provided care that was in line with the medical standard and deny claims that their actions (or inactions) caused harm, resulting in a "battle of the experts." The outcome of a medical malpractice lawsuit often comes down to which expert the judge or jury finds most credible.

Who Is Qualified to Be a Medical Expert?

Each state has its own medical expert requirements. An expert typically must come from the same field of medicine as the defendant. For example, if a case involves a surgical error, you'll need a surgeon to testify, not a primary care physician.

The best experts are doctors, nurses, and other professionals who are actively practicing medicine. Not only are they more up-to-date on the standard of care, but judges and jurors tend to find active experts more credible than experts who make a living testifying in court. Some states have special rules designed to prevent "career" experts, requiring that the majority of an expert's time be dedicated to practicing medicine.

Other expert qualifications may include:

  • board certification
  • publication in a professional journal
  • prior experience writing affidavits of merit and testifying in court, and
  • teaching experience.

Not all expert witnesses in medical malpractice cases are providers. Some cases may require a pharmacist to weigh in on drug interactions or a biomedical engineer to testify about a medical device, like an IVC Filter. A medical malpractice attorney will be able to find and hire the right type of expert for your case.

The Medical Expert's Testimony

A medical expert helps answer two critical questions in a medical malpractice case:

  • Did the defendant provide care that was consistent with the skill that a similarly-trained professional would've shown under the circumstances?
  • If not, did the doctor's sub-standard care cause the plaintiff's injury?

Standard of Care

A medical expert testifies about what a competent doctor would've done in the same situation as the plaintiff and defendant. For example, let's say a patient alleges that his doctor missed a cancer diagnosis. A medical expert would likely testify about tests a similarly-trained doctor would have run when presented with the same symptoms. If the defendant didn't run those same tests, the expert would say that the defendant didn't meet the standard of care.

Experts typically rely on their own training and experience as a basis for their opinion about the standard of care as well as medical publications and medical board guidelines.


An expert must also testify about whether the doctor's failure to meet the standard of care caused the patient's injury. Proving causation in a medical malpractice case can be difficult. Was the bad outcome caused by the doctor's sub-standard care or because of the disease or condition the doctor was trying to treat?

For example, let's say a patient claims that her baby's birth injury was caused by her obstetrician's negligence. Because of the complex interplay between maternal and fetal factors and the shared responsibility of the delivery team, it can be difficult to establish the cause of a birth injury. Only an expert—or a team of experts from different fields of medicine—would be able to potentially link the injury to the obstetrician.

How Soon Do I Need a Medical Expert?

Over half of the states in the United States require plaintiffs to get a medical expert's opinion before they can file a lawsuit. Plaintiffs in these states must either submit an affidavit of merit with their lawsuit or get the approval of a medical malpractice review panel before they can file.

Plaintiffs and defendants must disclose the substance of their experts' testimony to each other and to the court before trial. If either side fails to do so before the court's deadline, the court will either dismiss the plaintiff's case or enter a default judgment against the defendant unless the case falls into the rare category of medical malpractice cases that don't require an expert opinion.

Medical Malpractice Cases That Don't Require Experts

Some errors are so obvious that a jury doesn't need a medical expert to understand that the medical provider violated the standard of care. Classic examples include a surgeon who leaves an instrument in a patient's body or a psychiatrist who sexually assaults a patient.

In these types of cases, a rule called "res ipsa loquitur" (Latin for "the thing speaks for itself") may apply. When res ipsa loquitur comes into play, the plaintiff doesn't need an expert witness. For the rule to apply, the plaintiff must prove:

  • the plaintiff was harmed while under the care of the medical professional
  • the harm wouldn't have happened unless the professional was negligent, and
  • the plaintiff didn't contribute to the harm.

As a practical matter, it's not wise to assume that you don't need an expert because the provider's fault seems obvious to you. Talk to a lawyer before you conclude that res ipsa loquitur applies to your case.

Learn more about res ipsa loquitur in medical malpractice cases.

Do I Need a Lawyer's Help Finding an Expert Witness?

You can effectively represent yourself in some types of personal injury cases, like minor workers' compensation claims or property damage claims. Medical malpractice cases aren't that type of case.

Of course, you technically can file a medical malpractice lawsuit without a lawyer, but malpractice cases are complex. You need a deep understanding of legal and medical issues to win and you have to navigate more rules and deadlines than a typical injury case requires.

As noted, in dozens of states, you need a medical expert before you can even file a malpractice lawsuit. A lawyer can advise you on whether it's worth investing in an expert and help you find a qualified expert that judges and jurors trust. Experienced medical malpractice lawyers know how to find a medical expert in any specialty. Some work with medical expert witness services and others rely on experts they've successfully worked with in the past.

Talk to a Medical Malpractice Lawyer

Dealing with any medical issue is challenging. But feeling like the treatment that was supposed to make you better, actually made you worse, is devastating. A lawyer can help you figure out what went wrong and what to do about it.

Don't delay. Each state sets a deadline—called the "statute of limitations"—for filing medical malpractice claims. If you wait too long, the court won't hear your case and you'll miss your opportunity to get compensation for your losses.

If the expense of hiring a lawyer is holding you back, keep in mind that most medical malpractice lawyers get paid a percentage of what you win, under what's called a "contingency fee agreement." If you lose, you won't have to pay a lawyer's fee.

Learn more about how to pay for a medical practice lawyer and how to find the right lawyer for your medical malpractice case. You can also connect with a lawyer directly from this page for free.

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