Merely breaching established standards is not enough to support a medical malpractice lawsuit. Once a breach of standards has been established by expert testimony, the plaintiff must establish that the breach was the proximate cause of the injury. For example, assume that the patient is brought to the emergency room with severe injuries from a motorcycle accident. After a prolonged stay in the intensive care unit (ICU), the patient ultimately loses his leg. Upon discharge from the hospital, the patient has an attorney investigate the care he received in the ICU. The attorney finds that the patient was repeatedly given the wrong dosage of his antihypertensive medication, and, as a result, his blood pressure was out of control. Although this is a clear breach of the standard of care, the attorney also must prove, by expert testimony, that the incorrect dosage of medication caused the loss of the leg. Showing that the standard of care was breached and that the patient has an injury is not enough. The attorney must demonstrate that but for the incorrect dosage of medicine, the patient would still have his leg.

Causation is a problematic defense. Juries are not sympathetic to a physician who acts negligently and then claims that the patient’s injuries are not due to the substandard care. Since there is usually an element of punishment in a verdict against a physician, jurors tend to focus on the negligent behavior and ignore whether the negligence actually caused the injury. They believe the physician should not escape punishment because the patient was lucky enough to escape injury. Causation defenses work best when the physician’s behavior is below the acceptable standard but is not obviously dangerous. A physician who misses a shadow on a lung film may successfully argue that the tumor was too far advanced for an earlier diagnosis to matter. A physician who refuses to continue caring for a pregnant woman because her insurance lapses at 34 weeks will have difficulty convincing a jury that this was unrelated to her baby’s brain injury.