Standard medical malpractice requires proving that the defendant's treatment fell below the applicable standard of care and caused the plaintiff's injury. An informed consent claim asks a different question: did the provider give the patient enough information to make a genuinely informed decision about whether to undergo the treatment at all? The California Supreme Court established the modern informed consent framework in Cobbs v. Grant, 8 Cal.3d 229 (1972), holding that a physician owes a duty to disclose to the patient all information material to the patient's decision, meaning all information that a reasonable patient would consider significant in deciding whether to undergo the proposed procedure. Cobbs replaced the earlier professional standard, under which adequacy of disclosure was measured against what a reasonable physician would have disclosed, with a patient-centered standard that puts the decision where it belongs: with the patient.
The Elements of the Informed Consent Claim
Under California law, an informed consent claim requires proof of four elements: the physician had a duty to disclose information material to the patient's decision; the physician failed to disclose that information; a reasonable patient in the plaintiff's position would have refused the procedure or chosen a different treatment option if the information had been disclosed; and the undisclosed risk that materialized caused the plaintiff's harm. The first two elements are typically established through medical expert testimony. The third element is governed by an objective patient standard, not by what the specific plaintiff would have decided, which is an important distinction for both pleading and trial strategy.
The Materiality Standard: What Must Be Disclosed
A risk is material and must be disclosed if a reasonable patient would attach significance to it in deciding whether to consent to the proposed treatment. Materiality is determined by the combination of the probability that the risk will materialize and the severity of the harm if it does. A low-probability risk that results in permanent disability or death is material; a high-probability risk of a minor, transient complication may not be, depending on its significance to the patient's decision. Unusual risks with very low probability of occurrence but catastrophic consequences are the center of most informed consent disputes: the surgeon who fails to disclose a 0.5 percent risk of paralysis in a spinal procedure, where paralysis is the outcome, has almost certainly violated the informed consent obligation regardless of whether that probability was small.
Medical expert testimony is typically required to establish both what risks were material and what a reasonable physician should have known about them at the time of the procedure. Plaintiff counsel should work with the expert to establish the medical literature on the relevant risk, the standard disclosure practices for the procedure type, and any evidence that the defendant specifically knew of this patient's heightened risk profile that would have made the materiality analysis different for this particular patient.
Causation: The Objective Patient Standard and Its Strategic Implications
The causation element in an informed consent case is the most frequently contested at trial. The defendant will argue that the plaintiff would have consented to the procedure anyway, because the procedure was medically necessary or because a reasonable patient with the plaintiff's medical condition would not have refused it. California uses an objective standard for the causation inquiry: would a reasonable patient in the plaintiff's position, with the plaintiff's medical history and condition, have refused the procedure if the undisclosed risk had been disclosed?
The objective standard is a double-edged analytical tool. It prevents plaintiffs from prevailing simply by testifying that they personally would have refused, which most plaintiffs will claim after the outcome is known. But it also requires the defendant to show that a reasonable patient would still have consented, not merely that the plaintiff had no reasonable alternative, which is a different and harder burden than it first appears. In cases involving elective procedures, the reasonable patient causation argument is substantially stronger for the plaintiff, because a reasonable patient who was fully informed of a material risk of a serious outcome in an elective procedure has a credible argument that the procedure would not have been chosen. In cases involving emergency or medically necessary procedures, the defendant's causation defense is correspondingly stronger.
The Consent Form Defense
Defendants almost universally rely on the written consent form as evidence of disclosure. The consent form typically lists a range of potential complications, often in general terms, and the patient's signature is offered as proof that the specific risk was disclosed and accepted. California courts have held that a signed consent form is evidence of disclosure but is not conclusive. A form that lists complications in general terms, such as infection, bleeding, or nerve damage, without specifically identifying the risk that materialized and its specific probability, may not constitute adequate disclosure of a material risk. The adequacy of the form's disclosure is itself a fact question that medical expert testimony addresses.
Plaintiff counsel should obtain the specific consent form used in the patient's procedure and compare it against medical literature on the procedure's known material risks. A consent form that omits a known and well-documented risk, or that buries it in a list of minor complications without identifying its significance, supports the argument that the form did not constitute adequate informed consent for the specific risk at issue. For the broader medical malpractice standard-of-care framework and the expert testimony requirements for both standard-of-care and informed consent claims, the medical-malpractice category covers the range of med-mal theories in detail. Where an informed consent failure leads to the patient's death rather than a surviving injury claim, the wrongful death damages analysis is covered in the wrongful-death category. For case-law developments on informed consent materiality and the objective patient causation standard in California and federal courts, the case-law-settlements archive tracks the significant opinions.