Informed Consent: When Not Warning You Is Malpractice

A patient can be told, correctly, that a surgery went exactly as planned — and still have a valid malpractice claim. Informed consent is not a formality attached to a procedure; it is its own independent duty, and failing it is malpractice regardless of how skillfully the procedure itself was carried out.

Quick answer: Informed consent is a separate duty from competent treatment — a flawlessly performed procedure can still be malpractice if a material risk was never disclosed. States use one of two tests for what counts as material: the reasonable physician standard (what practitioners customarily disclose) or the reasonable patient standard from Canterbury v. Spence (what a reasonable patient would want to know). The claim also has its own causation requirement — that adequate disclosure would have changed the treatment decision — and it is legally distinct from battery, which applies where no consent was given at all.

A Duty Separate From Competent Treatment

Our guide to the four elements of a medical malpractice claim covers the standard duty to provide competent care. Informed consent imposes a second, independent duty: before a patient agrees to treatment, the provider must disclose enough information for that agreement to be a genuinely informed choice.

This means the two duties can fail independently of each other. A surgeon can perform a procedure to the highest technical standard and still be liable for informed consent malpractice if a material risk went undisclosed and then materialized. Conversely, full and adequate disclosure does not excuse a negligently performed procedure — the two claims can coexist, or either can stand alone.

Two Tests for What Must Be Disclosed

The reasonable physician standard

Asks what a reasonable practitioner in the same field would customarily disclose under similar circumstances — essentially a professional-custom test, structurally similar to the ordinary standard-of-care analysis in other malpractice claims. Under this standard, expert testimony about customary disclosure practices plays a central role.

The reasonable patient standard

Established in Canterbury v. Spence, 464 F.2d 772 (D.C. Cir. 1972), this test instead asks what a reasonable patient in the plaintiff’s position would consider material to the decision whether to proceed — independent of what physicians customarily disclose. The court’s reasoning was that the right to decide belongs to the patient, not the profession, so the measure of adequate disclosure should be patient-centered rather than defined by physician custom.

States are genuinely split on which test governs, and the choice matters practically: under the reasonable-patient standard, a plaintiff can potentially prevail even where the defendant’s disclosure matched what other physicians in the field customarily provide, if a reasonable patient would still have wanted more.

The Claim’s Own Causation Problem

Even where inadequate disclosure is established, the claim requires a further showing: that adequate disclosure would have changed the treatment decision. Courts differ on whether this is measured:

• Subjectively — would this specific patient, given their own values and circumstances, have declined or chosen differently
• Objectively — would a reasonable patient in this position have declined or chosen differently

Defendants frequently argue that no reasonable patient would have declined treatment given the alternative — an untreated serious condition — which can defeat the claim even where the disclosure itself was genuinely inadequate. This causation hurdle is often the harder part of the case, not the disclosure failure itself.

Not the Same as Battery

Battery applies where a procedure was performed with no consent at all, or on a fundamentally different body part or procedure than what was authorized — operating on the wrong knee, or performing a more extensive procedure than the one consented to, without an emergency justification. Informed consent malpractice instead applies where consent was actually given, but the disclosure preceding it fell short of what the law requires.

The distinction matters because the two theories carry different elements, different defenses, and in some states different damages treatment. A claim pleaded under the wrong theory can fail even where the underlying facts would have supported the other one — worth flagging to an attorney early rather than assuming the two are interchangeable.

The Narrow Exceptions

• True emergencies, where obtaining consent is not practically possible before treatment is medically necessary
• Therapeutic privilege, recognized in a limited number of states, allowing narrow withholding of specific information reasonably believed likely to seriously harm the patient’s decision-making or health — a disfavored, narrowly construed exception rather than a general escape hatch
• Patient waiver, where a patient affirmatively declines to be informed of specific risks

What Actually Decides These Cases

• The signed consent form, though a generic or boilerplate document carries less weight than it may appear to
• Contemporaneous chart notes describing the actual conversation, which frequently matter more than the form itself
• Standard informational materials the practice or hospital used for that specific procedure
• Testimony from both sides about what was actually discussed
• Expert testimony on what risks were material given the patient’s specific condition and circumstances

Practical Steps

1. Request the complete record, including the signed consent form and any pre-procedure notes, not just the discharge summary.
2. Write down what you actually remember being told, and by whom, as soon as possible — memory of a specific conversation degrades quickly and is powerful evidence while fresh.
3. Identify the specific risk that materialized and whether it was ever mentioned to you in any form.
4. Confirm which disclosure standard your state applies — reasonable physician or reasonable patient — since it changes what evidence is actually relevant.
5. Get a qualified medical expert’s opinion on whether the risk that occurred was one a provider in that specialty should have disclosed.
6. Consult an attorney before assuming this is the same claim as ordinary treatment negligence — the two can and often do coexist, but they are proven differently.

Sources & Further Reading

• Canterbury v. Spence, 464 F.2d 772 (D.C. Cir. 1972) — the landmark reasonable-patient materiality standard for informed consent disclosure
• Restatement (Second) of Torts § 892 — the general framework distinguishing consent from its absence, underlying the battery/malpractice distinction discussed above
• State informed consent statutes and case law, which vary in which disclosure standard applies and in whether therapeutic privilege is recognized
• See our guides to the four elements of a medical malpractice claim for the underlying negligence framework this duty sits alongside, and misdiagnosis and diagnostic error claims for the separate diagnostic-duty theory that most often gets confused with an informed consent claim