Do you need an expert witness to sue for medical malpractice in Washington?

By Michael Shemtoub, trial attorney, Beverly Law. Updated November 2026.

What RCW 7.70.030 and 7.70.040 require you to prove

Washington’s medical negligence law is in chapter 7.70 RCW. Under RCW 7.70.030, no award can be made for an injury caused by health care unless the plaintiff proves at least one of three things: the provider failed to follow the accepted standard of care, the provider promised the patient that the injury would not occur, or the patient did not consent to the care.

For the first path, RCW 7.70.040 lists two elements:

• Breach. The provider failed to exercise the degree of care, skill and learning expected of a reasonably prudent provider in the same profession or class, in Washington, at that time, acting in the same or similar circumstances.
• Causation. That failure was a proximate cause of the injury.

Both elements turn on medical practice and medical cause, which is why experts sit at the center of nearly every Washington case.

When Washington courts require an expert, and who can serve

The Washington Supreme Court set out the rule in Harris v. Groth (1983). Expert testimony is generally required when an essential element is “best established by an opinion which is beyond the expertise of a layperson,” and medical facts must be proven by experts unless they are “observable by [a layperson’s] senses and describable without medical training.”

In McLaughlin v. Cooke (1989), a vasectomy case, the court agreed that no expert testified the doctor breached the standard of care in performing the vasectomy itself. The jury verdict stood on the claims about care after surgery, because the patient’s expert testified that the doctor’s failure to remove a hematoma sooner was a proximate cause of the complications.

The rule can decide a case before trial. In Young v. Key Pharmaceuticals (1989), the court held that “a defendant may move for summary judgment on the ground the plaintiff lacks competent medical evidence to make out a prima facie case of medical malpractice.” The plaintiff must then answer with evidence, such as an expert’s affidavit.

The expert need not always be a physician. Harris held that a nonphysician is not automatically barred from testifying as an expert in a malpractice case, and that the trial court decides whether the witness is qualified. In Young, though, a pharmacist’s affidavit was not competent evidence of the standard physicians owe in dosing medication. In Frausto v. Yakima HMA, LLC (2017), the court held that an advanced registered nurse practitioner may be qualified to testify on causation if the trial court finds the ARNP meets Evidence Rule 702.

The narrow exceptions for obvious mistakes

In Young, the court said that where deciding negligence “does not require technical medical expertise, such as the negligence of amputating the wrong limb or poking a patient in the eye while stitching a wound on the face,” testimony by a physician is not required. McLaughlin described the same idea: no expert is needed if the conduct is “such a gross deviation from ordinary care that a lay person could easily recognize it.”

Causation follows a similar rule. Frausto said expert testimony on causation is always required except in the few situations where understanding it “does not require technical medical expertise.” McLaughlin added that if a reasonable person can infer the causal link from the facts and the medical testimony given, the evidence can be enough.

Birth-injury claims rarely fit the exception. How a fetal heart tracing should have been read or when a cesarean delivery should have been called are questions of technical medical judgment, so a family should plan on expert review of both the care and the cause of the child’s condition.

Informed consent claims under RCW 7.70.050

A claim that a provider failed to obtain informed consent has its own elements under RCW 7.70.050. The provider did not tell the patient a material fact about the treatment, the patient consented without knowing it, a reasonably prudent patient in similar circumstances would not have consented if told, and the treatment caused injury.

The statute says certain material facts “must be established by expert testimony,” including the recognized alternatives and the recognized serious possible risks and complications. In a recognized health care emergency, when the patient cannot consent and no authorized person is readily available, consent to required treatment is implied.

In Smith v. Shannon (1983), the Supreme Court split the question in two. Expert testimony is “necessary to prove the existence of a risk, its likelihood of occurrence, and the type of harm in question.” Once those facts are in evidence, the jury decides without an expert whether a reasonable patient would have found the risk significant.

Why striking the certificate of merit did not remove the expert

Enacted in 2006, RCW 7.70.150 required a plaintiff to file, when starting the case, a certificate of merit signed by a health care provider qualified as an expert, stating that there was “a reasonable probability that the defendant’s conduct did not follow the accepted standard of care.” In Putman v. Wenatchee Valley Medical Center (2009), the Supreme Court held the requirement unconstitutional. It unduly burdened the right of access to courts by limiting plaintiffs’ ability to conduct discovery, and it violated the separation of powers by conflicting with the judiciary’s power to set court procedures. The Legislature’s records list the section as repealed in 2023.

A separate rule in RCW 7.70.100 once required 90 days’ notice before a malpractice suit could begin. In Waples v. Yi (2010), the court held that the notice requirement conflicted with Civil Rule 3(a), which governs how a lawsuit is commenced, and so violated the separation of powers. Today RCW 7.70.100 addresses mandatory mediation before trial.

Neither ruling changed what a plaintiff must prove. The burden in RCW 7.70.040 remains, and a defense motion under Young can test it once the case is underway.

Time limits in brief

Under RCW 4.16.350, a malpractice suit must be filed within three years of the act or omission, or one year from when the patient or the patient’s representative discovered or reasonably should have discovered that the injury was caused by it, whichever expires later. The statute still prints an eight-year outer limit. In Bennett v. United States (2023), the Washington Supreme Court ruled that the eight-year repose period breaks article I, section 12 of the state constitution, the privileges and immunities clause. The plaintiff there alleged a brain injury whose cause was not diagnosed until the eight years had run.

The rules for a child’s own claim and for public hospitals are on our Washington birth injury deadline page.

What this means for your case

• Request the complete records, including fetal monitoring strips, labor and delivery nursing notes and the newborn chart.
• Write down what you were told about risks and options before the delivery, and when. An informed consent claim turns on what was disclosed.
• Do not wait for a final diagnosis to start. Expert review and the three-year clock run at the same time.
• Expect the defense to test the expert evidence. A case without qualified support on both breach and causation can be dismissed before trial.

Beverly Law reviews Washington birth-injury cases. Learn more on our Washington birth injury page, or call (310) 552-6959 for a free consultation in English or Spanish. You owe no fees or costs unless we win.

Common questions

Related pages

Washington birth injury lawyers · Birth injury statute of limitations in Washington · Birth injury damages in Washington · Beverly Law in Washington · Personal injury statute of limitations in California, Texas and Washington · More injury law FAQs

Important: This page is general information, not legal or medical advice, and reading it does not create an attorney-client relationship. Every case is different; talk to a lawyer about yours. Last reviewed: November 10, 2026.