Recent Changes in the Admissibility of Biomechanical Expert Testimony in Delaware

Delaware's Supreme Court recently decided a trio of cases concerning the admissibility of biomechanical expert testimony. Biomechanics is the study of "the mechanical bases of biological, especially muscular, activity; also: the study of the principles and relations involved." [1] The decisions, Eskin v. Carden,[2] Mason v. Rizzi,[3] and Potter v. Blackburn[4] have changed the manner in which biomechanical expert testimony can be offered into evidence in Delaware. In these cases, the Delaware Supreme Court, for the first time, held that biomechanical expert testimony is admissible when offered to show a relationship between the force of a collision and the resulting injuries. [5] The Court did, however, place substantial limitations on those who would proffer such evidence. The Court held that trial judges cannot admit biomechanical expert testimony unless the method of evaluation used is properly calibrated in such a way as to take into consideration the particular medical history of the party against whom the evidence is being offered, so as to be sufficiently reliable. [6]

I. Biomechanical Expert Testimony

A. Early Applications of Biomechanical Testimony

Attorneys in Delaware first employed biomechanical expert testimony in products liability litigation. For example, in General Motors Corporation v. Dillon, plaintiff sued General Motors and Union Park Pontiac for damages purportedly stemming from a single-vehicle collision, allegedly caused by a defective steering column. [7] Plaintiff claimed that the car's "energy absorbing steering column" detached from the dashboard and caused him to crash into several parked cars. [8] Defendants countered with the expert testimony of mechanical and biomechanical engineer, Dr. Edward Moffatt, Ph. D. , who testified that the steering column would only collapse when subjected to pressure exceeding 1,400 pounds, a force that is greater than any human could exert. [9]

In Mazda Motor Corporation v. Lindahl, the decedent's family sued Mazda for negligence in the design of "yielding seats," which plaintiff claimed was the cause of her husband's death. [10] Plaintiff attempted to offer into evidence the testimony of seat design expert, Louis D'Aulerio, who would have testified that the negligent design of the seat caused decedent to partially eject from the car. Defendants moved to disqualify Mr. D'Aulerio on the grounds that he was not competent to testify on the issue of causation, as he was neither a medical expert nor a biomechanical engineer. [11] The Superior Court granted defendant's motion. Defendants also moved for a Directed Verdict on the grounds that plaintiff failed to offer sufficient evidence demonstrating proximate cause. The Superior Court disagreed stating that while biomechanical expert testimony may have been helpful to the jury, plaintiff had presented adequate evidence on the issue of causation. [12]

The Supreme Court reversed, holding that plaintiff failed to prove her prima facie case of negligence when she failed to offer expert testimony on the issue of causation. Further, because plaintiff's claim was based in part on the crashworthiness doctrine, it was incumbent on plaintiff to "establish that the injuries actually received in an accident with a defective product are greater than the injuries that would have been received in an accident with a non-defective product." [13] The court went on to state that when the issue of proximate cause requires a higher level of understanding of the underlying principles involved, outside the realm of which the jury is expected to be familiar, the absence of expert testimony bars a jury determination. Because plaintiff offered no evidence establishing a relationship between the seat collapse and decedent's injuries, thereby leaving the jury to improperly speculate on the issue of causation, the Superior Court improperly denied defendant's Motion for a Directed Verdict. [14]

B. The Use of Biomechanics in Low-Impact Collision Litigation

In recent years, biomechanics has gained increased prominence in the area of personal injury litigation on the issue of the forces involved in a vehicular collision. Traditionally, personal injury attorneys paid little attention to the forces stemming from a vehicle collision. Where property damage and injuries were more extensive, though, plaintiffs would show the jury enlarged photographs depicting the seriousness of an accident, implicitly drawing a correlation between the significant property damage and the severity of plaintiff's injuries. [15] Alternatively, defense attorneys litigating "fender-benders" made use of photographs of accident scenes where there was little to no vehicle damage to assert that the forces exerted in the collision were insufficient to cause plaintiff's injuries. [16]

In response to the increased use of these arguments, the Delaware courts began to require that parties attempting to make use of such claims or defenses do so via expert testimony. [17] This in turn has induced many personal injury litigants to call biomechanical engineers as expert witnesses. Typically, biomechanical engineers are called to testify that the forces present in a particular accident could (or could not) have caused the injuries complained of. Their opinions are based on an analysis of the dynamics involved in a particular collision, as well as studies documenting test subjects' reactions to varying levels of force. [18] Because the use of biomechanical expert testimony is a relatively recent phenomenon, the law pertaining to the admission of such evidence became quite unsettled.

II. Early Delaware Case Law

A. Davis v. Maute

In Davis, the Delaware Supreme Court held that parties in personal injury litigation cannot contend, whether directly or by implication, that a relationship exists between the degree of property damage and the severity of a party's injuries, without also offering expert testimony on the issue. [19] In Davis, defendant Franz Maute ran a red light, causing an accident with plaintiff Rosetta Davis. The plaintiff alleged that she suffered severe personal injuries as a result of the accident. The defendant conceded the issue of liability, leaving only the issues of causation and damages to be decided by a jury. [20]

At trial, plaintiff's expert medical witnesses testified that the accident caused permanent soft tissue damage to plaintiff. Conversely, defense counsel made several statements referring to the accident as a "fender-bender." The defense also enlarged several photographs of the plaintiff's vehicle to demonstrate there was only minor damage to plaintiff's car. The combined actions of defense counsel thus impliedly argued that the collision itself could not have caused plaintiff's injuries. [21] The jury ultimately awarded plaintiff $8,766, which the judge subsequently increased to $12,000 in granting plaintiff's Motion for Additur. Plaintiff appealed on the grounds that defense counsel made prejudicial statements relating to the cause of plaintiff's injuries, and also that the photographs were improperly admitted. [22]

The Supreme Court deemed defense counsel's references to the collision as a "fender-bender" an inappropriate attempt to implicitly argue that the collision could not have given rise to the plaintiff's injuries. [23] With respect to the enlarged photographs of plaintiff's vehicle, the court similarly found that the photos were improperly used to convey a message to the jury that since the collision resulted only in minor property damage, the plaintiff's injuries were negligible. [24] The Court also held that while the photographs might serve some valid defense purpose, pursuant to Del. R. Evid. 403 the court must employ a balancing test to determine whether the risk that the jury might draw improper inferences substantially outweighed the photographs' probative value. [25] Given that the defendant conceded the issue of liability, and because the Superior Court failed to issue a limiting instruction to the jury to avoid drawing correlations between the damage to plaintiff's car (or lack thereof) and the extent of her injuries, the Supreme Court held that the photographs were erroneously admitted into evidence. [26]

B. Kelly v. McHaddon

The Delaware Supreme Court in Davis held that an expert witness is needed when parties

make the argument that there is a reasonable correlation between the degree of property damage and the extent of a party's injuries. The Court did not, however, address the qualifications that an expert must possess in order to testify on such an issue. It was not until the Superior Court decided Kelly v. McHaddon that a Delaware court considered the issue of whether a biomechanical engineer is qualified or sufficiently competent to testify as to the relationship between property damage and physical injuries. [27]

In Kelly v. McHaddon, the Superior Court of Delaware granted plaintiff's Motion in Limine, excluding the testimony of a biomechanical engineer set to testify for the defense. [28] Catherine Ford, Ph. D. , would have testified that plaintiff's injuries were not a result of a December 13, 1997 collision with the defendant. The defense argued that the damage to plaintiff's vehicle and the injuries sustained by plaintiff as a result of the accident were minor. Further, defense argued that the force of the impact did not rise to the level of that which would cause permanent injury. [29] Plaintiff responded with a plea to the court to honor its "gatekeeping" duties, and exclude the controversial biomechanical expert testimony. [30]

The issue was one of first impression for the Delaware Courts. Judge Slights noted that while he could find no decision holding that biomechanical expert testimony is inherently unreliable, when such evidence lacks certain indicia of reliability or trustworthiness, the expert witness requirement in Davis is not met. [31] The Court also reviewed the various jurisdictional treatments of biomechanical testimony, and found one particular line of reasoning to be the best approach: a party may offer the testimony of a biomechanical expert witness pertaining to the potential loading in a particular accident and the general effect those forces would have on the human body, but the expert witness cannot testify as to the cause of the specific injuries resulting from the collision. [32]

In effect, Kelly added several important considerations for trial judges, beyond the mere requirement that there be expert testimony. First, the testimony of the expert must be reliable, both in terms of the qualifications of the expert as well as the methodology chosen by the expert in coming to his conclusion. Moreover, the court held that because biomechanical engineers are not medical doctors, they are not qualified to testify about a party's specific injuries. [33] One unresolved issue that remained after Kelly, though, was whether biomechanical expert testimony can ever be offered when not supported by the testimony of a medical doctor. The court in Kelly allowed Dr. Ford to testify on issues not pertaining to medical causation, reasoning that the risk of juror confusion did not outweigh the relevancy of the evidence because the defense offered Ford's testimony contemporaneously with Dr. Errol Ger's, who relied upon the former's findings. For this reason, the court held that the jury would not be confused or forced to unnecessarily speculate on the issue of causation. [34]

III. Recent Delaware Cases

A. Eskin v. Carden

On December 3, 1998, Robert Chickadel struck Barbara Carden's vehicle from behind. After the first collision, Mr. Chickadel put his vehicle into reverse and then struck Ms. Carden's vehicle a second time. Later that day, Carden went to the Emergency Room with pain in her lower back and legs. Nine months later, she underwent back surgery. Carden subsequently filed suit, and Marla Eskin, the executrix of Robert Chickadel's estate, conceded liability for the accident, leaving only the issue of Carden's injuries to be litigated. [35]

Prior to the trial, the Delaware Superior Court granted plaintiff's Motion in Limine excluding the expert testimony of Lawrence Thibault, D. Sc. [36] Thibault, an expert in the area of biomechanics, would have testified that the forces exerted in the collision could not have caused the injuries that plaintiff complained of. Thibault claimed that the forces, or "loading," within the collision were even less than those plaintiff incurred in normal activities (i. e. : walking or lifting). [37] The Superior Court held Thibault's testimony inadmissible because it had no probative value, and because the evidence was not "tied in" with the medical facts of the case. [38] At the conclusion of the trial, the jury awarded plaintiff $580,000. 00. Defendant appealed the trial judge's grant of the Motion in Limine.

The Delaware Supreme Court affirmed the holding of the Superior Court, but upon very different grounds. For the first time, the Delaware Supreme Court addressed the admissibility of biomechanical expert testimony pertaining to the correlation between the loads resulting from a collision and the cause of a party's injuries, an issue about which biomechanical experts could not previously testify. [39] Unlike in Kelley, the Court in Eskin held that biomechanical expert testimony that "bridges the gap between the general forces at work in an accident determined by physical forces analysis . . . and the specific injuries suffered by the particular person who was affected by those forces" is admissible. [40] But while the Supreme Court seemingly opened the door for the increased use of biomechanical expert testimony, they placed a number of substantial hurdles in the path of those who would make use of such evidence. Testimony on the issue of causation is admissible only where the trial judge has first made a finding that the evidence is relevant and reliable, and that its relevance is not substantially outweighed by the prejudicial effect stemming from the danger that the jury would be confused or misled. [41] The Eskin Court also held that biomechanical expert testimony is admissible for impeachment purposes when used to counter a medical expert's testimony. [42]

In determining whether proffered expert testimony has sufficient indicia of reliability and trustworthiness, the Court instructed that expert testimony must provide the jury with "definitive evidence" that the forces involved in a "particular" collision caused, or could not have caused, the specific injury in question. [43] In coming to such a conclusion, the trial judge therefore must find that the methodology employed by the expert witness sufficiently takes into consideration the specific medical history of the individual. Without a showing that the conclusions drawn by the biomechanical expert witness can appropriately be applied to a specific individual, the testimony has no relevance.

Additionally, the Delaware Supreme Court reiterated that absent a "special nexus" between the evidence of a general response or common behavior and the facts of a given case, evidence pertaining to the generalized response has the potential to be extremely prejudicial to the opposing side. [44] Therefore, if the party proffering the evidence cannot show that the studies employed by the biomechanical expert adequately took into consideration the unique medical condition of an individual, there is a high risk of danger to the party against whom the evidence is offered. A jury may incorrectly believe that the generalized response of the average person would be the same response that plaintiff would have had in the collision. On the other hand, if a particular individual has no pre-existing medical conditions, and the studies and tests performed on the "average individual" adequately reflect the projected response of the individual in question, it is possible that the biomechanical expert witness' testimony could be admissible on the issue of causation.

In Eskin, plaintiff had previously undergone back surgery. The studies and literature used by Thibault in coming to his final conclusions did not, however, address the anticipated responses of accident victims with pre-existing back injuries. Consequently, the proposed testimony of the biomechanical expert witness lacked the required degree of reliability. [45] The Eskin Court also found that the probative value of the evidence was substantially outweighed by the danger that the jury would give undue deference to the opinions of Dr. Thibault. The jury would have erroneously believed that the plaintiff's reaction to the collision would have fallen within the measured statistical range for normal individuals, when in fact plaintiff was uniquely susceptible to injury. [46] Therefore, the Superior Court properly granted plaintiff's Motion in Limine.

B. Mason v. Rizzi

On May 8, 1998, Plaintiff Maria Rizzi and Defendant Judith Mason were involved in a low-impact vehicle collision that did not result in any property damage. Defendant admitted liability for the accident, which left only the issues of causation and the nature and extent of plaintiff's damages (alleged soft-tissue and cervical disc injuries). [47] Plaintiff had previously suffered a disc herniation, leaving her particularly vulnerable to physical injuries.

The Superior Court granted plaintiff's pre-trial Motion in Limine, excluding the expert testimony of biomechanical engineer, Peter Cripton. Defendant had wanted to admit into evidence Cripton's expert opinion that the forces exerted on plaintiff in the accident were no greater than those experienced in daily activities. Cripton would have also testified that the loads placed upon plaintiff could not have caused her injuries, as the forces were relatively minor. [48]

The trial judge gave two justifications for the exclusion of Cripton's testimony. First, the court stated that the testimony was not relevant because there was no corroborating medical testimony on the issue of the relationship between the forces involved in the accident and plaintiff's injuries. [49] The court held that without medical testimony to substantiate Cripton's theories, the prejudice to the plaintiff would outweigh what little probative value Cripton's statement possessed. [50] The second reason given by the court for the exclusion of Cripton's testimony was that the studies used by Cripton in coming to his conclusions were based on the average person, having no previous medical condition. [51] In Mason, the plaintiff had previously undergone surgery for a back condition. Consequently, Cripton's conclusions possessed little relevant value. The trial judge held that if the studies performed on the normal person were presented to the jury, there was a risk that the jury would be misled into believing that plaintiff's injuries would have been akin to those of the average person. [52] Defendant appealed the Superior Court's grant of the Motion in Limine. [53]

The Delaware Supreme Court began with the premise that the admission of biomechanical expert testimony is "contextual." [54] Justice Steele cautioned trial judges that prior to the admission of such evidence, they must thoroughly examine the purposes for which the biomechanical expert's testimony is being offered. Trial judges should look to see that the research used by the biomechanic in drawing their conclusions is reliable and able to be validated. [55] In Mason, the trial judge properly found that Cripton's testimony was not reliable, largely because the studies he used did not take into consideration plaintiff's prior back injury, and therefore the testimony wasn't "sufficiently tied to the facts of the case." [56] Cripton's testimony would have been based on the average person's generalized response to the forces of the accident. Barbara Carden was not the average person, and therefore the studies performed on the average person were inapplicable to her. Justice Steele did not, however, accept the trial court's finding that in order to admit biomechanical expert testimony, it must be corroborated with other medical expert testimony. [57] Biomechanical expert testimony is admissible, even when its not supported by corroborating medical testimony, or used by the medical expert in coming to his or her own findings. [58]

Justice Steele gave a helpful example as to when biomechanical expert testimony would be admissible. [59] When a medical expert testifies that a patient reported that her head struck the dashboard in a collision, and the physician uses the statement to confirm that the cause of her injury was the force of the collision causing her to strike the dash, a biomechanic could testify that no individual of plaintiff's size or general condition could have been thrust into the dashboard. There is no reliance on such information by a medical expert, however, the conclusion can be found to have been reliably formed, and may therefore be relevant to defendant's case. The trial judge should look to see that the studies used by the biomechanical expert were statistically significant with respect to the plaintiff's particular body shape and size. Also, the judge would need to determine that there were no prior medical conditions that may have made plaintiff particularly susceptible to injury, thereby rendering biomechanical studies on the average person irrelevant. If the trial judge can make such findings, there would be little chance that the jury could be confused or misled because the statistical data measuring the range of responses elicited by the average person would encompass the plaintiff's probable reaction.

C. Potter v. Blackburn

In the most recent case dealing with this issue, the Delaware Supreme Court, in Potter v. Blackburn, held that a medical expert was not qualified to testify as to the relationship of the forces involved in a collision and the cause of the plaintiff's specific injuries, when the basis of such a conclusion is an estimate of property damages. [60] In Potter, the plaintiff claimed that she suffered a rotator cuff injury resulting from a collision caused by defendant. In response to plaintiff's expert witnesses who testified that the accident caused plaintiff's injuries, defendant offered the testimony of Dr. Errol Ger. Dr. Ger testified that based upon his interview and evaluation of plaintiff, as well as inspection of a photograph of plaintiff's vehicle, plaintiff's injuries were not caused by the collision. [61] Both sides moved to disqualify the other's medical experts on the ground that they were not qualified to testify as to the cause of plaintiff's injuries. The Superior Court denied both motions. [62] Plaintiff appealed, claiming that Dr. Ger's opinion was based solely on a photograph of plaintiff's car, which incurred damages of approximately $800. 00. The Superior Court's denial was premised on the belief that Dr. Ger's opinion was based on more than just a single photograph -- Dr. Ger had interviewed and examined plaintiff. [63] On appeal, though, plaintiff raised a new argument, claiming that Dr. Ger's opinion was based on the inconsequential damage plaintiff's vehicle sustained. However, because plaintiff raised the issue for the first time on appeal, the Supreme Court did not address the validity of the new argument. [64]

Plaintiff's second ground for appeal surrounded the trial judge's grant of Defendant's Motion in Limine, excluding a portion of Dr. Ger's testimony. On cross-examination Dr. Ger was asked whether his opinion would be different had he known that the total property damage to defendant's vehicle exceeded $3,000. 00, to which Dr. Ger answered in the affirmative. [65] The Supreme Court affirmed the Superior Court's decision. The Court held that Dr. Ger's remarks related to the significance of defendant's property damage, concerned an area about which he was not sufficiently competent to testify. [66]

The Supreme Court cited to Eskin and Mason in support of its holding that Dr. Ger was not qualified to testify about forces in a collision based on the level of resulting property damage. [67] When a party offers testimony to draw a correlation between property damage incurred (or lack thereof) and the cause of a particular individual's injuries, Davis requires that such a showing be made via expert testimony. Medical experts are competent to testify about the cause of parties' injuries (as their "expertise [is] limited to medicine"), however, they cannot base their opinions about the cause of the injuries, solely on the degree of property damage originating in a collision. [68] Biomechanical engineers, on the other hand, through the use of "physical force analysis (whether it be ëphysics' or ëengineering')," may be sufficiently competent to draw such conclusions and render an opinion on the relationship between the three competing factors. [69]

In many ways, the Supreme Court in Potter takes the issue of biomechanical expert testimony full circle. In Davis, the court addressed the admissibility of evidence that drew a correlation between property damage and resulting injuries. The Court held that evidence of that relationship was admissible only when offered in conjunction with the testimony of an expert. In Kelly, the court held that while biomechanical engineers are competent to testify about the forces created within a collision and the general impact those forces would have on the human body, they are not competent to testify about the medical cause of an individual's injury. Judge Slights unequivocally stated, "biomechanical engineers are not doctors." However, in Eskin and Mason, the Supreme Court held that biomechanical engineers, under circumstances which provide sufficient guarantees of reliability and validity, may testify about the relationship between the forces involved in a collision and a party's subsequent injuries. And in Potter, the court held, in effect, that doctors are not biomechanics. Their expertise is limited to the field of medicine, and they are not therefore competent to testify about the "force of impact based on damage to a vehicle," thereby effectively eliminating medical experts' ability to testify about the relationship between the extent of property damage and the nature of a party's injuries in accordance with the requirements set forth in Davis.

IV. The Uncertain Future of Biomechanical Expert Testimony

The recent Delaware Supreme Court decisions in Eskin, Mason and Potter clarified confusing law on the admissibility of biomechanical expert testimony, but also created more questions. On the one hand, the Court, for the first time, formally recognized biomechanics as a legitimate field of study and indicated that biomechanical expert witness findings are not per se unreliable. [70] However, in the same breath, the Court also placed significant limitations on the use of such testimony by requiring trial courts to make a finding that the testimony possesses indicia of reliability and trustworthiness. In coming to such a conclusion, the trial judge must be assured that the studies and literature upon which the expert bases his conclusions on, adequately take into consideration an individual's body type and pre-disposition to injury.

The primary issue that still remains unclear is when the expert must utilize a specialized set of studies. The Court failed to clearly indicate exactly when a party who suffers from pre-existing conditions, does so to such a degree and extent that the individual's experience in the collision is unable to be compared to that of the average person. Does a prior back surgery, regardless of the procedure's seriousness, rule out the admissibility of comparative biomechanical studies? What if the back surgery occurred 5, 10, or 15 years ago? And what about other forms of previous medical conditions -- does a plaintiff's sprained ankle require that an expert witness re-create entire studies consistent with plaintiff's minor medical condition?

Another area that remains unresolved is the admissibility of biomechanical testimony in cases where the issue of liability is in contention. In both Eskin and Mason (as well as Davis and Kelly), the defendant had conceded liability for the accident, leaving only the issue of causation and damages for a jury determination. It is unclear whether biomechanical evidence might have a different application when the jury is determining the issue of negligence. Similarly, it is unclear what effect, if any, the most recent Supreme Court cases will have in other areas of law as the line of cases from Davis to Potter involved low-impact collisions only.

The one thing that the Supreme Court has been very clear on, though, is that the admissibility of biomechanical expert testimony is largely a fact-specific issue, to be determined on a case-by-case basis by the trial judge. The trial judge is charged with the responsibility of scrutinizing the proffered testimony to determine "whether the expert and the ëfield of expertise' itself can produce an opinion that is sufficiently informed, testable and in fact verifiable . . . [such that the trial judge is] satisfied that the generalized conclusions of the biomechanical expert are applicable to a particular individual." [71] Because the Court declined to establish a bright-line rule, attempts to offer biomechanical evidence will have to be addressed by the trial court, based on the specific facts present in the case.

Somers S. Price, Jr. is a partner at Potter Anderson & Corroon LLP who has almost thirty years of experience in products liability cases, having represented Fortune 500 corporations, including major motor vehicle manufacturers, in many trials in the Delaware courts. Roxanne Houtman is a rising third-year law student at the Syracuse University College of Law. The views expressed in this article are those of the authors and may not represent the views of Potter Anderson & Corroon LLP or its clients.