The Graves’ claims centered on a software design defect theory involving “spaghetti code,” defined as a condition when computer code becomes unstructured and creates “a rather tangled  mess.”   Id. Three  experts  were  utilized  to  support  the  Graves’  theory,  initially identifying three potential causes: hardware error, software error, and complaint error.  Id.  All three  experts  opined  that  software  error  was  deemed  the  most  probable  cause  after  the possibilities of hardware and complaint error were ruled out by them.  Id. at 654.  CAS moved to exclude all three experts, contending that their testimony was not reliable because each relied on reports of other alleged failures to support their conclusion that software error was the cause. Id.at 654-55. The trial court excluded the three experts and granted summary judgment.

The Graves court began its exclusion analysis by acknowledging that an expert, in certain circumstances, can base his conclusion on a form of differential diagnosis—that is, by “eliminating the likely causes until the most probable one is isolated.”  Id. at 656.  The Court limited the admissibility of a differential diagnosis opinion, however, by holding that the opinion “must provide a reasonable, objective explanation for the rejection of possible alternative causes in order for the opinion to be admissible under Rule 702.” Id.   Based upon that holding, the Court segued into the use of the substantial similarity test.   The Graves court noted that the experts “improperly relied on [FDA] reports of other failures to bolster their conclusions that software error was to blame.” Id. at 657.

In reaching that conclusion, the Court articulated the relationship between the substantial similarity test and the requisite reliability of an expert’s opinion.  It began its analysis with the rule: “[e]vidence of other similar incidents is admissible where there is some special relationship between the accidents tending to prove or disprove some fact in dispute.”  Id. It then turned to the test: “[a] plaintiff bears the burden of demonstrating that the products are similar, the alleged defect is similar, the defect caused the other accidents, and there are no other reasonable secondary explanations.”  Id.  Applying this test, the Court noted that “[w]hile the products in the FDA report are similar to the one here, the record contains no evidence suggesting any further connection to or whether a software error was even involved in these other cases.”   Id.   The Court concluded that “[i]n order to deem these other incidents substantially similar, we would have to automatically equate an alleged failure with a software defect of the kind claimed by the Graves without any evidentiary basis for doing so.”  Id.  The Court stated that it would not make that evidentiary leap. Because the underlying incidents were not proven to be substantially similar, expert opinions based on them were not reliable.  Accordingly, the Court affirmed the exclusion of the expert witnesses and the granting of summary judgment.

The legal underpinning for the Graves decision derives from the significant case of Watson v. Ford Motor Co., 699 S.E.2d 169 (S.C. 2010).  The Watson case addressed the application of the substantial similarity test in the context of a “sudden acceleration,” design defect claim involving a Ford Explorer.  The plaintiffs alleged that electromagnetic interference (EMI) caused the Ford Explorer’s cruise control to malfunction, resulting in sudden and uncontrollable acceleration of the vehicle.  According to the opinion, “EMI is an unwanted disturbance caused by electromagnetic radiation that interferes with an electric circuit.”  Id. at 173.

Watson and the Estate of Carter (“the Plaintiffs”) brought design defect claims alleging that the “Explorer’s cruise control system was defective because it allowed electromagnetic interference (EMI) to affect the system.”  Id. In an effort to bolster their design defect claims, the Plaintiffs sought to introduce evidence of other incidents where a Ford Explorer allegedly accelerated in a sudden or unintended manner.  Over the objection of Ford, the evidence was admitted at trial.  The jury returned a verdict against Ford, awarding “$15 million to Watson and $3 million to the Estate of Patricia Carter.”  Id.

On appeal, Ford argued, among other grounds, that the trial court erred by admitting evidence of other incidents. The South Carolina Supreme Court agreed and established the test later cited in the Graves decision above.   In analyzing the other incident evidence, the Court noted that the Plaintiffs introduced a deposition of a “former Ford employee who investigated a number of claims of unintended acceleration of Explorers driven in Britain.”   Id. The former employee testified to an e-mail that “referenced ‘35 incidents that have been categorized as unexplainable’ in which the vehicles suddenly accelerated.” Id. The Plaintiffs also presented testimony  from  three  witnesses  that  had  experienced  “sudden  acceleration”  in  their  Ford Explorers when their “cruise control would not disengage.”  Id.  Based upon its review of that evidence, the Court held that the trial court abused its discretion in admitting it.

The Court listed a number of reasons why the other incident evidence did not meet the substantial similarity requirements.  “First, the products were not similar because most of the other incidents involved Explorers that were made in different years from the Watson Explorer and were completely different models with the driver’s seat located on the right side of the vehicle.”  Id. The Court also noted that the plaintiffs “failed to show a similarity of causation between the malfunction in th[eir] case and the malfunction in the other incidents.”   Finally, honing in on the requirement that the alleged defect be the same, the court noted that the Plaintiffs “only presented the testimony of the other drivers and did not present any expert evidence to show that EMI was a factor in the malfunction in the other incidents.” Id.

Based upon the inadequacies in the other incident evidence, and the Plaintiffs’ failure to show that the other incidents were caused by the same alleged design defect, the court ruled that the evidence was not relevant: “[T]his evidence was not relevant because [Plaintiffs] failed to show that evidence of these incidents made the existence of the EMI defect in this case more probable.”   Id. at 179.  The court also pointed out that this type of evidence is “highly” and “extremely” prejudicial, and for that reason, the plaintiff must “establish a factual foundation to show substantial similarity.” Id. at 179-80. The Court noted that, “counsel highlighted this improper evidence in closing arguments and thereby possibly induced the jury to speculate as to other causes of the accident not supported by any evidence.”  Id. at 180.  Based upon the trial court’s error in admitting the other incident evidence, and other evidentiary failures, the Court reversed the judgment for Plaintiffs and entered judgment for Ford.

Emily, the three year old daughter of Steven K. Funkhouser, died after receiving severe burns while playing unattended in the Funkhouser’s Ford Windstar.  Mr. Funkhouser filed a product liability lawsuit against Ford Motor Company for failure to warn of the risk of fire while the vehicle is not in operation.  The plaintiffs alleged that the daughter was playing inside the family’s 2001 Ford Windstar, while the keys were not in the ignition and the car was turned off. Id. at 311.  A fire engulfed the passenger side of the van, and severely burned Emily, which ultimately led to her death. Id.

According  to  plaintiff’s  expert,  the  fire  was  caused  by  “heat  energy  generated  by abnormal and undesired electrical activity within the lower portion of the center instrument panel in the vicinity of the wiring harness, cigarette lighter and the controls for the vehicle’s heating and air conditioning system.”  Id.  Further, the expert opined that the source of ignition was most likely electrical activity coming from one of the wires or connectors in that vicinity.  Id.  He also concluded that Ford possessed information that should have put it on notice that these particular Ford Windstar minivans were unreasonably dangerous for the use for which they were sold.  Id. at 311.  Funkhouser sought to introduce evidence of seven other Windstar fires, but the trial court excluded the evidence.

The evidentiary battleground centered upon the cause of the seven other Windstar fires. The Court noted that, “[i]n the present case, all Funkhouser can show is that the incidents occurred under substantially the same circumstances; he cannot show that the fires were caused by the same or similar defects.”   Id. at 314.   Based upon that weakness in the other incident evidence, the Court held that the trial court properly excluded the other Windstar fires. Id.

Funkhouser further challenged the trial court’s evidentiary ruling, however, by arguing that application of the substantial similarity test to a failure to warn claim “actually results in an evidentiary threshold that is higher than what is required to prove the merits of his claim.”  Id. Funkhouser argued for a relaxed test in a failure to warn claim because “liability under a failure to warn claim does not require a showing of any defect, only a showing that the manufacturer knows or has reason to know that its product is dangerous.”  Id. Accordingly, he argued that the proper test should allow a plaintiff to interchange the words “defect” and “dangerous.”

After enunciating the substantial similarity test, including its causation prong, the court rejected Funkhouser’s argument for a relaxed similarity test and concluded that removing the “defect requirement from the causation prong would allow a plaintiff to attribute notice and actual knowledge to a manufacturer based on the mere existence of a generalized danger.”  Id. The court recited the common rejoinder that “a manufacturer is not an insurer of its product’s safety.”   Id. Therefore, in order for the subject evidence to be admissible, the court held that Funkhouser was required to show that the other Windstar fires were caused by “the same or similar defect.”  Id. at 315.

Similar to the Graves court’s refusal to allow an expert witness to opine that a product’s software was defective based upon an FDA report showing similar products had failed, the Funkhouser court tracked the same line of reasoning.  It noted that, “Funkhouser is asking this Court to invert the test and infer similar causes, i.e., defects, from the existence of similar effects, i.e., fires.” Id. at 314.  As a matter of logic, the Court noted that “[t]his inversion simply does not work: although a faulty cigarette lighter may cause a key-off dashboard electrical fire, not all key-off dashboard electrical fires are caused by a faulty cigarette lighter.”  Id.  Accordingly, the court concluded that the seven prior incidents along with the accompanying expert testimony were properly excluded.

Finally, Stokes v. Ford Motor Co., 300 P.3d 648 (Mont. 2013), is a significant case because it demonstrates that the foundational requirement of substantial similarity can serve as a powerful grounds for the exclusion of other incident evidence.  In Stokes, plaintiff took an aggressive position with respect to the discovery of voluminous other incident information.  The court entertained, but ultimately denied, a motion for discovery sanctions.  At the trial of the case, however, the court excluded all of the other incident evidence because the plaintiff failed to provide the proper foundation. The Montana Supreme Court affirmed.

In Stokes, Peter Andrew Carter, an Australian resident, rented a “2002.5” Ford Explorer while in Montana on business.  Stokes, 300 P.3d at 650.  On November 7, 2007, while driving on the highway, Carter collided with another car at a speed between 76 and 83 miles per hour.  Id. The impact resulted in the vehicle rolling five times over a distance of 286 feet.  Id.  Carter was partially ejected from the vehicle and killed.  Id.  Dennis Stokes, the personal representative of the Carter estate, filed a wrongful death and survival claim against multiple defendants. Id.

Stokes alleged that the Ford Explorer was defectively designed because a safer design alternative existed “to protect the driver during [a] rollover.”  Id. at 650.  Stokes alleged that the subject  Ford  Explorer  should  have  contained  a  Safety  Canopy  System  (SCS),  which  was available three months before the Explorer at issue was manufactured.  Id. at 650-51. Although the SCS was available as an option feature, it was not implemented in the subject Ford Explorer as standard equipment.  Id. at 651.

At  the  trial  of  the  case,  Stokes  sought  to  introduce  other incident  evidence  that  he “independently obtained,” consisting of a summary compilation of over 3,000 crashes which was offered to establish that Ford had actual notice of Explorer rollovers.  Id. at 653.  Ford objected to the introduction of the evidence, noting that “there has to be some base level showing of substantial similarity” for the introduction of this evidence. Id. Stokes failed to provide the foundation that his other incident evidence was substantially similar, and the court excluded the evidence. Id. at 653-54.

The Montana Supreme Court began its consideration of that ruling by noting that “[e]vidence of other similar instances may be admitted to show notice or knowledge of the existence of a danger or a defect.”  Id. at 654.  Further, “[t]he test of admissibility for evidence of the accidents in a product liability case is whether the circumstances surrounding the product involved in other accidents were substantially the same or similar to the accident at issue.” Id. Important to the foundational requirement, the court also stated that “[a] concerted effort should be made by [the trial] court to allow the admission of evidence of only those accidents where both the product and the circumstances surrounding the accident were similar to the case at bar.” Id.