I Won't Testify Against Another Physician: Plaintiff vs Defense Expert Work

By John Mahoney · August 19, 2026

It is the most common reason doctors decline expert work, and it rests on a misunderstanding of what the field actually is.

The objection, stated fairly

Most physicians who refuse this work are not being lazy or squeamish. They are expressing a real professional value: loyalty to colleagues who practice under impossible conditions, and a suspicion that the malpractice system punishes bad outcomes rather than bad care.

That suspicion is not baseless. Which is exactly the argument for participating rather than abstaining.

Roughly half the field is defense work

Defense retention is not a niche. Every case with a plaintiff expert has a defendant who needs one.

Someone has to explain to twelve people with no medical training why care that produced a terrible outcome was nevertheless reasonable. Why a differential that missed the rare diagnosis was appropriate given what was knowable at 3 a.m. Why a complication is a recognized risk rather than a deviation. Why the retrospective clarity a plaintiff's attorney is describing did not exist in the moment.

The physician best equipped to make that argument is one who has stood in that exact position — under time pressure, with incomplete information, making the same call.

If you believe the system too often mistakes bad outcomes for bad care, defense work is where that belief becomes useful. Declining to participate does not protect colleagues. It leaves the explaining to someone else.

The case for doing both

New experts often assume they must pick a lane. The physicians with the longest careers in this work generally do not.

The reason is practical. An expert who has only ever worked one side gets impeached with that fact in every single deposition: Doctor, in eleven years you have never once concluded that a physician met the standard of care, have you? There is no good answer. The pattern becomes the testimony.

Working both sides makes that question a non-event. It also keeps the reasoning honest, which is the real point — if your conclusion tracks who hired you, you are not an expert, you are an advocate with a medical degree, and eventually someone will demonstrate that on the record.

Meritless cases die faster when good physicians review them

Here is the part that reframes the objection entirely.

Cases without merit are screened out by experts who say so. When a qualified, honest physician reviews a file and tells the retaining attorney there is no deviation, that case usually ends — before it consumes years of a colleague's life.

Plaintiff attorneys do not want unsupportable cases; they are expensive to lose. They rely on expert review to tell them which claims are real.

So the physician who refuses all plaintiff-side review is not preventing suits against colleagues. They are ensuring that the screening gets done by whoever is willing to do it, which may be someone less qualified, less current, or less scrupulous.

Rigorous experts on both sides are what make the system approximate justice. Abstention just cedes the ground.

Genuine deviations exist

The honest version of this argument has to include the other half.

Some care is genuinely below standard, and the patients harmed by it have no path to remedy that does not require a physician willing to say so. Not a hired gun — a careful practitioner willing to state that a specific act fell outside what a reasonable colleague would have done.

Refusing that role categorically is a position. It is worth being clear-eyed that the position has a cost, borne by someone.

What the boundary actually is

The line worth holding is not plaintiff versus defense. It is honest versus captured.

Practically, that means: form your opinion before you learn which conclusion would help. Decline cases outside your genuine scope. Tell the retaining attorney when their case has no merit and expect to be paid for that review. Keep your fee schedule identical regardless of side. Refuse to shade a conclusion because of who signed the retainer.

An expert who does all of that has nothing to defend on cross, and nothing to apologize for at a specialty meeting.

The reframe

You are not being asked to testify against physicians. You are being asked to state, accurately, what a reasonable physician in that situation would have done — and to do it whether that helps the plaintiff or the defense.

That is not disloyalty. It is the same judgment you already exercise at morbidity and mortality conference, peer review, and every time a resident asks whether a decision was right.

The only difference is that this time, someone is paying you for it, and the answer has consequences beyond the room.