Scientific Expert Testimony Crucial, Must Offer Objective Explanation

Every tort has elements established by either common or statutory law which must be proven in order for the plaintiff to prevail. For example, negligent conduct without resulting damages does not constitute an actionable negligence claim in the eyes of the law. Product liability claims are no different. Plaintiffs must show that they were injured by a product but also that the injuries were caused by a product in an unreasonably dangerous, defective condition. If one element is not proven, then the plaintiff cannot prevail. In cases involving complex, scientific issues, expert testimony is often necessary to prove the design defect. Recently, the South Carolina Supreme Court addressed the difficult burden plaintiffs face in proving these necessary legal elements.

In Graves v. CAS Medical Systems, Inc., Op. No. 27168 (S.C. Dec. 12, 2012), the plaintiffs filed suit against CAS Medical Systems following the death of their 6-month old daughter. The girl was one of three triplet daughters ordered to be connected to an in-home monitor manufactured by CAS to track breathing and heart patterns. By design, the monitor would sound a loud alarm if the girl stopped breathing or her heart rate slowed. Despite being monitored by the machine, the girl died one night of Sudden Infant Death Syndrome (SIDS). The plaintiffs allege that the monitor’s alarm never sounded.

Subsequently, the plaintiffs sued CAS, alleging that the monitor’s software design caused the monitor to fail. As an over-simplified summary of their theory, they alleged that the software was “jumbled,” causing the alarm signal to occassionally get lost on the way to its destination. There was no dispute that the harware functioned properly. To support their claim, the plaintiffs retained three software experts to testify that a defect caused an alarm failure. None of the experts did much actual testing of the hardware, relying instead on so-called differential diagnosis theory. Because the plaintiffs were not woken by the alarm, it must not have sounded, at least according to the experts. Because the hardware was not defective, then the software was to blame. Sounds like good logic.

At trial, CAS moved to have the experts’ testimony excluded on the grounds that it did not meet the reliability factors for scientific testimony. In turn, CAS moved for summary judgment because without the expert testimony, the plaintiffs could not prove a design defect. The Court agreed that the experts’ testimony was not reliable and granted CAS’ motion for summary judgment.

On appeal, the Supreme Court agreed with the trial court in finding that the experts’ testimony was unreliable. The Court indicated that when relying on differential diagnosis, the expert must provide a reasonable, objective explanation for the rejection of alternative causes. Apparently, the “because they said so” explanation was insufficient. As the Court noted, there was substantial evidence that complaint error was a real possibility. The monitor’s internal record keeping system noted that the alarm sounded. The girl’s pediatrician opined that the plaintiffs slept through the alarm due to the extreme exhaustion of raising triplet infants. Moreover, the monitor successfully recorded the girl’s declining heart rate and breathing cessation. None of this evidence appears to have been accounted for by the experts.

Without the expert testimony, the Court held that the plaintiffs’ could not prove the injury was caused by a defective condition – an essential element of a product liability claim. The plaintiffs had to offer some evidence beyond a potential failure to show that it was unreasonably dangerous. Because the allegations involved complex software issues, expert testimony was necessary. Without it, the plaintiffs could not support their claim.

We here at Abnormal Use know not whether the monitor’s software was in fact defective, but neither do those experts. There simply was not enough evidence. While some extenuated logic could deduce that the software was defective because the alarm was not heard, it doesn’t account for alternative explanations. Further, simply because something was not heard does not mean it didn’t sound. Expert testimony must still account for some objective criteria – or plaintiffs run the risk of overlooking essential elements of their claims.

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