Computer Expert Testimony Inadmissible Without Objective Reasons for Eliminating Alternate Causes in Death from Software in Design Defect Case

When a premature baby was sent home, her doctor ordered that her vital signs be tracked using a monitor manufactured by the defendant. The monitor was supposed to sound an alarm if the baby’s heart rate became fast or slow or if her breathing rate slowed. The baby died of Sudden Infant Death Syndrome (SIDS) while hooked up to the monitor. The monitor correctly tracked the baby’s decreased breathing rate and erratic heart rate. However, her parents and other family members claimed no alarms sounded.


The parents sued the manufacturer of the monitor for a strict liability design defect arguing that the monitor’s software contained a defect which caused the alarms not to sound. Three computer experts were to testify that the monitor failed due to software error. One neonatologist was to testify that the parents could have resuscitated their baby had the monitor worked correctly. The manufacturer moved to exclude all of the plaintiffs’ proposed expert witnesses arguing that the computer experts were unreliable and the neonatologist was not qualified as an expert. The trial court granted this motion. The manufacturer then filed a motion to dismiss which the trial court granted. The parents appealed.


The Supreme Court of South Carolina modified and affirmed the appellate decision. Specifically, the court found that the trial court abused its discretion when it held the neonatologist was not qualified as an expert. However, even if the neonatologist’s testimony had been admitted, the trial court was correct in granting the defendant’s motion for summary judgment because the claim could not survive without the computer experts’ testimony because the design defect claim was too complex to be within the ken of the ordinary juror.


A court considers three factors when determining whether to admit expert testimony. First, the court considers whether the subject matter requires an expert at all, that is whether it is beyond the ken of the ordinary juror. Second, the court considers whether the witness has the requisite knowledge and skill to qualify as an expert in the subject matter. Third, the court considers whether the substance of the testimony is reliable.


The trial court correctly held that the plaintiffs’ computer experts’ testimony that a software defect caused the monitor’s alarm to fail was unreliable. There are two different tests for the reliability of expert testimony: the four-factor test for scientific testimony and an ad hoc evaluation for nonscientific testimony. The court held that regardless which test applied, the plaintiffs’ computer experts’ testimony failed.


All three computer experts explained that they came to their conclusions using the reasoning to the best inference methodology, where potential causes of the harm are identified and then either excluded or included based on their relative probabilities. Three things could have caused the monitor to fail to alert the parents of their daughter’s condition. First, the hardware could have been defective. Second, the software could have been defective. Third, the parents could have slept through the alarm, which is also described as “complaint error.” Subsequent testing of the specific monitor at issue eliminated hardware error. While the plaintiffs’ experts could address the probability of software error, they failed to provide objective criteria for eliminating complaint error.


The trial court abused its discretion in holding that the plaintiff’s medical expert was not qualified to render an expert opinion regarding SIDS. An expert need not be a specialist in the particular branch of the field at issue. The medical expert had been a practicing neonatologist for thirty years and regularly encountered SIDS in her practice. She also kept current with the literature on SIDS.


The parents’ claim nonetheless failed because it was too complex to be within the ken of the ordinary juror. Therefore, they were required to produce expert testimony regarding the design defect. Once the plaintiffs’ computer experts’ were excluded due to lack of reliability, the plaintiff’s failed to meet this requirement.


See: Graves v. CAS Medical Systems, Inc., 2012 WL 3793263 (S.C., August 29, 2012) (not designated for publication).