For any plaintiff to succeed in a malpractice suit, the courts require him or her to prove that the defendant had a duty to adhere to a particular standard of care, that there was a breach of this duty, and that the breach of the duty was the direct or proximate cause of the plaintiff’s injuries. These elements must be proved by a preponderance of the evidence. Zwiren v Thompson , 578 S.E.2d 862 (Ga 2003), provides excellent insight into the element of proximate causation. The facts are simple. The patient went to the defendant plastic surgeon, who performed an unnamed procedure on the plaintiff, and a year later a malpractice suit was filed asserting negligence by the defendant. At the close of trial, the judge issued the following instructions to the jury.

In order for the Plaintiff to show a medical cause and effect relationship, Plaintiff must present expert medical testimony showing that, within a reasonable degree of medical certainty, as proven by a preponderance of the evidence, that the injury in question was proximately caused by the negligence of the Defendant. Expert testimony on the issue of causation cannot be based on speculation or possibilities. It’s not sufficient for the expert testimony to show the negligence, if any, is only a possible cause of the Plaintiff’s injury, or that the alleged neglect merely might have caused the damages. If you find the Plaintiff has not proven to a reasonable degree of medical certainty by a preponderance of the evidence that the alleged damages were proximately caused by the Defendant’s neglect, then you would return a verdict for the Defendants.

The jury decided in favor of the defendant, and the plaintiff appealed. The appellate court reversed the trial court because the judge used the following phrase in his instruction to the jury, “within a reasonable degree of medical certainty.” Now it was the defendant’s turn to appeal. The Supreme Court of Georgia reversed the appellate court and reinstated the trial court’s verdict. In doing so, the court gives us a clear picture of the standard of evidence that is to be used in civil cases and what constitutes proximate cause.

The court stated that in civil cases, the standard to be used is “preponderance of the evidence” rather than “within a reasonable degree of medical certainty.” This standard is defined as “that superior weight of evidence upon the issues involved, which, while not enough to free the mind wholly from a reasonable doubt, is yet sufficient to incline a reasonable and impartial mind to one side of the issue rather than to the other.” OCGA § 24-1-1(5). “The standard requires only that the finder of fact be inclined by the evidence toward one side or the other.”

The court then discussed proximate cause. It stated that proximate cause is defined as “that which in the natural and continuous sequence, unbroken by other causes, produces an event, and without which the event would not have occurred.” In determining the factors that make up proximate cause, the court noted that they are “always to be determined on the facts of each case upon mixed considerations of logic, common sense, justice, policy, and precedent.”

In medical malpractice cases when one wishes to prove proximate cause by a preponderance of the evidence, one must do so through the testimony of an expert witness “because the question of whether the professional negligence caused the plaintiff’s injury is generally one for specialized expert knowledge beyond the ken of the average layperson.” The role of the expert then is to use his or her “specialized knowledge and training … [and] present to the jury a realistic assessment of the likelihood that the defendant’s alleged negligence caused the plaintiff’s injury.” It is through direct and cross examination of the expert witness that the expert professes his opinion on causation. The expert is required to “express some basis for both the confidence with which his conclusion is formed, and the probability that his conclusion is accurate.” The court in its summary of causation and the expert’s role in defining it stated that “Perhaps in the world of medicine nothing is absolutely certain. Nevertheless, it is the intent of our law that if the plaintiff medical expert cannot form an opinion with sufficient certainty so as to make a medical judgment, there is nothing on the record with which a jury can make a decision with sufficient certainty so as to make a legal judgment.” (cits. omit.)

The court then specified the expert witness’s duties regarding the element of proximate cause by stating that the expert’s testimony must provide a causal connection that is “more than mere chance or speculation,” and “that it must provide more than a mere or bare possibility that the alleged negligence caused the plaintiff’s injury.” Merely stating that it was “more likely that there was a possibility that the injury could have been avoided” and similar speculative statements is not a sufficient basis on which to find proximate cause. The court noted that “Instead of speaking in terms of possibilities, the expert’s testimony must show as an evidentiary threshold that the expert’s opinion regarding causation is based, at the least, on the determination that ‘there was a reasonable probability that the negligence caused the injury’.” The court continued by noting that “while certainty is not required, plaintiff must show a probability rather than merely a possibility that the alleged negligence caused the injury or death.” In other words, the expert must opine that whatever the defendant’s action or inaction was, it must be more than mere possibility, chance, or speculation that it caused the injury claimed.

The phrase “within a reasonable degree of medical certainty,” although sufficient on its face and surely expressing the expert’s confidence in his or her testimony, is accurate, but not required. A preponderance of the evidence “requires only that an expert state an opinion regarding proximate causation in terms stronger than medical possibility”; it must at least rise to the level of reasonable medical probability. The court then redirected its attention to the original jury instruction and, striking it, inserted the following instructions for prospective use.

In order for the plaintiff to show that the defendant’s alleged negligence was the proximate cause of the plaintiff’s injury, the plaintiff must present expert medical testimony. An expert’s opinion on the issue of whether the defendant’s alleged negligence caused the plaintiff’s injury cannot be based on speculation or possibility. It must be based on reasonable medical probability or reasonable medical certainty. If you find that the expert’s testimony regarding causation is not based on reasonable medical probability or reasonable medical certainty, then the plaintiff has not proven that the plaintiff’s injury was proximately caused by the defendant’s alleged negligence, and you would return a verdict for the defendant.

What you don’t know is that this was a 4-to-3 decision. The 3 dissenters agreed that the majority was wrong, since the law was quite clear. To prevail, a plaintiff is required to show that the injury in question was proximately caused by the defendant’s negligence, not by a reasonable degree of medical certainty but, rather, by a reasonable probability. Go back and reread the original jury instructions. The following phrase was repeated twice: “within a reasonable degree of medical certainty, as proven by a preponderance of the evidence.” This was the reason for the appeal: that the language was confusing. The appellate court stated that although it was not a perfect instruction, the language error was minor enough not to warrant a new trial. The Supreme Court disagreed.

The minority pointed out the clear meaning of the 2 terms. “Preponderance of the evidence” means the “superior weight of evidence, which, while not enough to free the mind wholly from a reasonable doubt, is yet sufficient to incline a reasonable mind to one side of the issue rather than to the other.” This is to be contrasted with a degree of medical certainty, which means a “state of being certain, as in the certainty of death,” “a state of being free from doubt,” and as something about which there is an “absence of doubt.” The minority believed that the contradictory definitions in the same sentence were confusing to the point that the instruction unfairly impacted the plaintiff. In the minority’s opinion, the appellate court got it right, and the plaintiff should have been granted a new trial. It’s sort of like that old saw, “say what you mean or you will never mean what you say.