To recover damages in a medical malpractice lawsuit, Wisconsin law requires the injured party to prove that the physician accused of negligence failed to provide the same standard of care that would have been provided by reasonably prudent physicians who practice in the same field of medicine and in the same locality. Expert testimony is nearly always required to establish both the prevailing standard of care and the negligent failure to meet that standard.

But does the medical expert need to rely on medical literature and other scientific data when he or she expresses an opinion about the prevailing standard of care? The Wisconsin Court of Appeals recently decided that the state’s version of the Daubert test allows medical experts to base their opinions on their own experience rather than published studies.

The malpractice case

The lawsuit alleged that a baby suffered nerve damage during its birth, causing a permanent disability in the baby’s left arm. The lawsuit was filed against the obstetrician who provided prenatal care to the mother. The obstetrician also delivered the baby.

Evidence at trial established that the baby’s shoulder became stuck (a condition known as shoulder dystocia) after the baby’s head emerged. After the baby was born, he was diagnosed with an injury that inhibits the growth and use of his left arm. The baby’s family attributed that injury to the obstetrician’s use of excessive traction to dislodge the shoulder during the baby’s delivery.

The plaintiff’s expert witness testified that the obstetrician erred in three ways. First, the obstetrician estimated the baby’s likely weight at birth by tracking the mother’s weight gain during her pregnancy. The expert testified that the obstetrician should have performed an ultrasound to estimate a more accurate birth weight. Knowing the baby’s actual birth weight (one pound and four ounces more than the obstetrician’s estimate) would have alerted the obstetrician to the heightened risk of shoulder dystocia.

Second, the expert testified that the obstetrician should have followed up an abnormal one-hour glucose test with a three-hour test to determine whether the mother had gestational diabetes. That condition can result in an elevated birth weight which again increases the risk of shoulder dystocia.

Finally, the expert testified that the obstetrician should not have performed a vacuum-assisted birth, given the mother’s weight and the baby’s birth weight. The expert opined that vacuum-assisted births are the largest risk factor for shoulder dystocia.

The jury concluded that the obstetrician was negligent. It awarded damages of almost $900,000.

Medical opinions compared to other expert evidence

Wisconsin has adopted a version of the familiar Daubert test, which permits the testimony of a qualified expert if it will be helpful to the jury, if the testimony is the product of reliable principles and methods, and if the witness has applied the principles and methods reliably to the facts of the case. The question in Siefert v. Balink was whether the expert based his testimony on reliable principles rather than personal preferences about the medical procedures an obstetrician should follow.

The defense founded its objection to the expert’s testimony on the expert’s failure to ground his opinions in medical literature. The Wisconsin Court of Appeals rejected that argument. The court relied on federal cases that recognize a distinction between medical evidence and other kinds of scientific evidence. The kinds of double-blind experiments that underlie statistical proof in other fields of science are often unavailable to medical experts given ethical prohibitions against experimentation on humans.

In addition, medicine is an uncertain science that addresses complex human organisms. It does not lend itself to the same level of certainty as physical sciences. Rather, it calls upon physicians to make sound judgments based on experience in addition to training.

Admissibility of the expert’s opinion

The expert based his opinion about known and generally accepted factors that determined the standard of care (birth weight, maternal obesity, and glucose testing) on his professional experience. The expert was not required to rely upon medical literature or on laboratory experiments in addition to his own experience as a basis for that opinion. The trial court noted that the Daubert standard is intended to shield the jury from “junk science” and determined that the expert’s training and experience assured that his opinions were not the product of junk science.

The court of appeals accepted the trial court’s reasoning. Although one part of the expert’s opinion was contradicted by medical literature that supported the obstetrician’s decision to regard the one-hour glucose test as normal, the expert was assessing the glucose test in light of the mother’s obesity and his own experience. It was up to the jury to weigh competing evidence and decide whether to believe the expert. The fact that an expert’s opinion can be impeached does not mean that the opinion is based on an unreliable methodology or that the methodology is not reliably applied to the facts of the case. Debatable evidence that is supported by experience should be assessed by the jury, not excluded from evidence.