Selection of Experts in an Auto Crashworthiness Case

By Mark P. Robinson, Jr. and Kevin F. Calcagnie


There are those who believe that most jurors in a complex automotive crashworthiness case pay little or not attention to expert witnesses, having made up their minds before the experts ever testify. There are others who believe that the experts for each side cancel each other out, much like reciprocals in a mathematical equation, resulting in a net effect of zero. While these theories may apply to a certain percentage of jurors, for the most part they listen to and are influenced by the evidence presented through experts. Experts can make or break an automotive crashworthiness case, and selection of the right experts can be as important to a successful result as the selection of jurors.

Experts must have exceptional professional qualifications, credibility and experience, along with the right combination of personal characteristics such as demeanor, speaking ability and personality. These qualities are essential in any litigation and will not be discussed here. This article will instead focus on the beginning of the selection process – identifying the areas of expert testimony that are typically necessary in preparing and presenting an automotive crashworthiness case. There are several categories of subject matter requiring expert testimony common to crashworthiness cases. These cases are frequently complex and require testimony from a variety of scientific disciplines.

Depending on the circumstances, the typical case will usually require testimony on several, and sometimes all, of the following:

  1. Accident reconstruction
  2. Biomechanics
  3. Human factors
  4. Materials and failure analysis
  5. Occupant kinematics
  6. Radiology
  7. Safety and design engineering

These are not mutually exclusive and there may be substantial overlap between one or more areas. A single individual may be qualified to testify in more than one category. For example, an automotive engineer may be qualified to testify as to both accident reconstruction and design safety. Likewise, two or more experts from completely different backgrounds may testify on some of the same subject matter areas. A biomechanic and a radiologist may both be qualified to testify as to the mechanism of a particular injury based on the physical evidence. A safety engineer and a human factors expert may both be qualified to render opinions regarding the necessity of warnings.

This is probably not an all-inclusive list, but it does cover the majority of areas of expert testimony usually necessary for a plaintiff to meet the burden of proof in a crashworthiness case. It also provides a checklist for identifying the types of experts that should be retained, as well as the potential issues that will be raised by the defense.


In any automotive crashworthiness case expert testimony will be required to reconstruct the accident. Resolution of the critical issues in the case will be dependent upon proof of precisely how the accident vehicle moved and how it became damaged. The entire sequence of events from pre-collision to impact to post-collision movement must be analyzed, in terms of vehicular movement, direction of force, speeds, and changes in velocity. The impact itself must be analyzed to determine which portion of the vehicle contacted another vehicle or fixed object, and at what point in time, and to determine specifically how the subject vehicle was damaged. This is accomplished by analyzing the accident site and damage to vehicles, including, but not limited to, scrapes, scratches, dents, paint transfers, contact marks and gouges.

Accident reconstruction will be probative on the issue of comparative fault, but is even more significant to the question of causation. The key issue in most crashworthiness cases is speed. The defense usually attempts to place the speed as high as possible in order to argue superseding cause – in other words, that the speed of the vehicle was so high, and the forces so great, that an alternative design would not have prevented serious injury. (Endicott v. Nissan, 73 Cal.App.3d 917, 926, 141 Cal.Rptr. 95 [1977])

For example, in an occupant restraint system case, the defense will argue that studies show in most collisions above 35 miles per hour serious injury can be sustained irrespective of seatbelt use. Speed can be critical because of the formula F=MV2. (Force equals Mass multiplied by the square of the Velocity). As speed increases geometrically, force increases exponentially. Doubling the speed will quadruple the force involved, and increasing the speed by 50 percent will more than double the force involved.

It is therefore essential to demonstrate the true speed of the vehicle or vehicles involved as precisely as possible. This is not a simple task as eyewitness testimony is frequently inaccurate, and skids are not always available to analyze with speed-from-skid formulas. Expert testimony cannot be based on speculation and conjecture. (Hyatt v,. Sierra Boat Company, 79 Cal.App.3d 325, 145 Cal.Rptr. 47 [1978]) Accurate speed estimates may require an analysis of the degree of crush exhibited by the vehicles. Most top-notch accident reconstruction experts use complex computer models derived from crash testing data, which utilize variables such as stiffness of the vehicles involved, weight, angle of impact, and degree of offset.

In addition to speed, accident reconstruction will usually be needed to resolve a variety of case-specific issues such as which component part ruptured a fuel tank, how many times a vehicle rolled over, or which roll caused the roof to crush in. Keep in mind that defense counsel will have their own reconstructionist whose job it will be to come up with a scenario most favorable to the defendants. A good accident reconstructionist is typically an engineer, knowledgeable in the basic laws of physics relative to motion, force and velocity, and has a background in analyzing motor vehicle accidents. Some accident reconstructionists may have experience in automotive design as well, which assists in proving how and why particular damage was sustained.


Aside from the question of reconstruction of vehicular movement, many crashworthiness cases will involve questions relating to how the occupants moved during the course of the collision. Another fundamental law of physics is that an object in motion tends to stay in motion. This is evident when a vehicle has decelerated rapidly and the occupants continue moving forward relative to the vehicle, causing them to strike portions of the interior of the vehicle such as the dash, windshield, pillars, or steering wheel. In these so-called “second impact” cases, where the occupant sustains injury due to contact within the vehicle, the issues of when, where and how the injured party’s body moved within the vehicle during the accident sequence can be pivotal on the issue of causation.

The defense will frequently contend that movement of the plaintiff’s body was such that the alternate design features suggested by plaintiff would not have made any difference. In a restraint system case, where the defect is the absence of a pelvic restraint, the defense will contend that the shoulder harness alone functions as well as a three-point lap and shoulder restraint system, and that even with a three-point system the plaintiff would have struck the interior and sustained severe injury. Therefore, it will be necessary for the plaintiff to demonstrate that under the circumstances of the accident a shoulder belt alone will not prevent serious injury, and that a child or small adult will submarine under the shoulder harness. The plaintiff must also demonstrate that a lap belt would have minimized occupant excursion such that no contact would have occurred.

Occupant kinematics also come into play in comparative fault issues. In one successful plaintiff’s case involving a defective seat back, the plaintiff sustained a spinal cord injury when her vehicle was rear-ended, throwing her into the rear seat area. The defendant argued that the plaintiff was at fault for not wearing her seatbelt. However, the plaintiff’s experts were able to demonstrate that even if she had been wearing the seatbelt, because of the failure of the seat back which caused it to twist inboard and rearward, her body would still have escaped the belt.

An expert in occupant kinematics should be able to address these types of issues, by demonstrating the precise movements of the plaintiff within the vehicle during the collision. This analysis can be based on a thorough examination of the physical evidence, including strike marks on the interior of the vehicle, loading marks on the seatbelts, and marks, bruises and lacerations on the plaintiff. In addition to physical evidence, crash test data may also provide the basis for such an analysis. There is a large body of literature available on occupant kinematics derived from testing, including vehicle-to-barrier tests using instrumented anthropomorphic dummies. (Although some tests have been conducted involving live anesthetized primates, California Evidence Code ß1159 prohibits their introduction into evidence in any product liability action involving motor vehicles.)

This data provides a reliable method for predicting how a human being will move in a variety of crash modes. It is also useful in creating a demonstrative animation to explain the expert opinions on occupant kinematics.


Closely related to the subject of occupant kinematics, the subject of biomechanics focuses on identifying the precise mechanism of injury with particular attention to medical evidence and the injury itself. Like occupant kinematics, biomechanical issues arise in the context of causation when there is a dispute as to which of two or more potential mechanisms caused the plaintiff’s injuries. The plaintiff may have a defective vehicle, but if a link between the injury and the design feature in question cannot be demonstrated, there is no case.

For example, in a typical rollover/roofcrush case involving a neck injury, the plaintiff may contend that the plaintiff sustained the injury due to the roof crushing down and striking the plaintiff’s head. However, the defense will invariably argue that the roll caused the plaintiff to dive toward the roof before it crushed, and that the injury was sustained during the diving impact, thus negating the lack of roof structure integrity as a cause.

Resolving this question requires a complex analysis involving not only occupant kinematics, but the injury itself and the specific factors necessary to bring about such an injury. What forces in terms of strength and direction were necessary to cause a fracture of this type? Is the fracture caused by axial compression or is there a flexion component? Were the G-forces in the rollover sufficient for a dive to the roof to cause a fracture of this type? Could the head of the belted occupant have ever struck the roof at all if there had been no intrusion into the passenger compartment? Are there injuries to the head which are consistent with a diving injury?

An expert knowledgeable in injury causation, a biomechanic, can answer these questions. Experts in biomechanics can have educational and employment backgrounds in a variety of subjects such as engineering, medicine, anatomy and physics. Some are physicians and others are engineers, while some are both. The role of the biomechanic is to evaluate both physical evidence, as well as medical records and documentation of plaintiff’s injuries, to determine the specific nature of the injuries sustained. By combining this with the evidence of conditions existing at the time of the collision and empirical data regarding forces necessary to produce particular types of injuries, the biomechanics expert can show the likely and probable causal mechanism of plaintiff’s injury. This will be instrumental in, and often essential to, the plaintiff in demonstrating the link between the plaintiff’s injury and the defective design or manufacture of the vehicle.


Occasionally, the expert testimony on biomechanical issues may be dependent upon an interpretation of radiological images. In certain cases, a major point of dispute may arise over exactly what the x-rays or CT scans show, and what they do not. In addition to disagreement between the plaintiff and defense experts as to how the injury came about, there is often disagreement as to what specific injury in fact occurred. For example, a defense tactic which is becoming increasingly popular in crashworthiness cases involving a second impact brain injury, is to contend that the injury is not caused by impact trauma. Rather, the defense contends that the plaintiff has sustained a diffuse axonal injury as a result of sudden deceleration, and that any traumatic injury was insignificant with respect to the actual brain damage. This permits the defense to argue that the speeds and dynamics of the accident itself were so great that plaintiff would have sustained injury irrespective of any proposed design feature that may have prevented a head strike, such as a better occupant restraint system or improved passenger compartment integrity.

In such a case, interpretation of radiological images becomes critical, and it may be unwise to rely on cursory and perfunctory radiology reports in the plaintiff’s records. However, frequently biomechanics experts are neither qualified nor comfortable rendering such opinions, preferring to rely on radiologists to examine x-rays and CT scans to determine the precise nature of the damage sustained.

A radiologist may be needed not only to support the opinion of the biomechanics expert, but to rebut the defense biomechanic. Depending upon the nature of the case, the plaintiff’s attorney may choose to use the radiologist as part of the case in chief, or merely as a consultant upon whose report the biomechanic relies (see Williams v. Volkswagenwerk Aktiengesellschaft, 180 Cal.App.3d 1244, 226 Cal.Rptr. 306 [1986], saving the radiologist for rebuttal if needed.


In order to prove that a product is defective, a plaintiff is not required to rely on expert testimony. (Campbell v. General Motors, 32 Cal.3d 112, 126, 184 Cal.Rptr. 891 [1982]) However, from a practical standpoint a successful crashworthiness case necessitates expert opinions to assist the jury in understanding issues relating to the nature of the defect, the degree of risk involved, the foreseeability of harm, and principles of design safety. Likewise, although the plaintiff does not have to prove a safer alternative design was feasible (Bernal v. Richard Wolf Medical Instruments Corp., 221 Cal.App.3d 1326, 1330, 272 Cal.Rptr. 41 [1990]), the jury will consider the economic and mechanical feasibility of safer alternative designs as part of its determination of whether or not a vehicle is defective in design. (Barker v. Lull Engineering, 20 Cal.3d 434 (1978); B.A.J.I. 9.00.5) Therefore, the plaintiff’s attorney should retain at least one expert in the field of automotive design safety, since it is a sure bet that the manufacturer will have outside experts, as well as in-house engineers defending the safety and the design of the subject vehicle.

The design expert should have a background in engineering, vehicle design and manufacturing processes, as well as safety and testing, preferably with the components of the vehicle in issue. This will enable the expert to evaluate the design feature in question, render criticism of the defect or defects, and discuss feasible alternatives. Design experts should be qualified to render opinions regarding what a reasonably prudent manufacturer should have done, and characterize the manufacturer’s conduct with regard to safety. (See, e.g., Hasson v. Ford Motor Company, 32 Cal.3d 388, 403, 185 Cal.Rptr. 654, 650 P.2d 1171 [1982]) This testimony should cover the issues relating to the defect, as well as negligence, notice and standard of care. The design expert can also be utilized to comment on testing, including what the manufacturer should have known from the testing it did conduct, as well as what the manufacturer could have discovered had it conducted adequate tests of the design in question.

Another role of the design expert may be to determine the validity of the manufacturer’s interpretation of test data, as well as its applicability to the issues in the case. In one successful crashworthiness case involving a defective occupant restraint system which failed to include a lap belt, the manufacturer’s primary defense was that the vehicle had performed better than the vast majority of vehicles produced by other manufacturers in crash testing pursuant to Federal Motor Vehicle Safety Standard 208. Even though the anthropomorphic crash test dummies struck the interior of the vehicle with their heads, they produced much lower HIC’s (Head Injury Criteria) and therefore in theory demonstrated a lower risk of head injury than vehicles with three-point systems where the dummies’ heads did not make contact. However, the plaintiff’s design engineer was able to demonstrate that the manufacturer’s reliance upon the test data was misplaced. The restraint system in question, unlike other systems tested, permitted the dummies to rotate outboard during frontal collisions into barriers, giving a false reading on the instrumentation and therefore invalidating the test results.

In addition to analyzing the manufacturer’s test documentation, the design expert should be familiar with industry literature showing what safer alternative designs were available and used by other manufacturers, as well as the extent of available industry knowledge from testing conducted by others.


Proving defects in crashworthiness cases is not as simple as saying the manufacturer should have used more metal and less plastic. Just as proof of causation requires expert testimony regarding the nature, extent and mechanism of damage to the plaintiff, proof of a defect may necessitate expert testimony on the same issues with respect to damage sustained by components of the vehicle. Likewise, just as a biomechanics expert may rely upon an analysis by a radiologist, the design engineer may benefit from an expert in analyzing the specific materials used in the defective component, and the precise mode of their failure. In a crashworthiness case, how and why a part or parts failed may be a key indicator of whether or not a particular vehicle was defective in design. An expert may be needed to testify as to whether a part broke as a result of an overload, fatigue or an imperfection in its manufacture. Another typical question is whether a part was designed such that it was capable of withstanding foreseeable impact forces.

For example, in a case involving a frontal collision in which a belted passenger sustained a spinal cord injury, it was contended that the plaintiff’s shoulder harness locking mechanism had not worked properly. Microscopic analysis of the retractor mechanism interior showed that the teeth on the plastic locking wheel had broken or chipped away, indicating that the retractor had not locked immediately, and had allowed a portion of the belt to spool out. This explained the absence of belt marks on the plaintiff and the chance fracture of a lumbar vertebral body due to the excessive pressure imparted by the lap belt. The plaintiff was able to establish that had a lightweight metal been used instead of the plastic which chipped away, the locking mechanism would have in all probability functioned as intended.

In addition to questions of defective design, many crashworthiness cases involve defects in manufacture which are a cause of a failed component and resulting injury. These defects may also require expert analysis as to how and why the material broke or failed. In another crashworthiness case, a woman sustained a severe head injury in a rear-end collision due to interior intrusion of the sheet metal from the side and rear of the vehicle. Analysis by a metallurgist and a welding expert demonstrated that several of the welds in the sheet metal were “cold welds” where the metal had not properly fused together. The effect was to cause a weaker structure than intended by the manufacturer, which permitted a significant increase in the deformation and intrusion into the occupant compartment during the impact.

Experts who testify specifically on the issues of materials and failure analysis can be used to supplement and support the opinions of design safety engineers. They should have familiarity with the materials used as well as manufacturing processes, since their testimony may be needed to address issues related to the failure, as well as inadequacy of materials used and the availability of better materials. They can also be utilized to evaluate quality control procedures and adequacy of testing performed by the manufacturer.


In some crashworthiness cases, particularly those involving an allegation of failure to warn or comparative fault, expert testimony on human factors is beneficial, if not essential, to countering certain defenses. A routine defense in crashworthiness litigation is that the plaintiff was wearing the seatbelt in an improper position, or was improperly seated, thereby defeating the belt’s effectiveness. The manufacturer will argue that the plaintiff was wearing the lap belt too high, that the seat was reclined too much, that the plaintiff was turned in the seat, or any one of a number of alleged misuses. The defense uses this to argue to comparative fault as well as product misuse.

A human factors expert can demonstrate how the alleged misuse is the result of confusing and often ambiguous instructions given in owner’s manuals concerning use of occupant restraint systems. Testimony on human factors can also show how inadequate and ineffective warnings regarding the consequences of failure to follow instructions to the letter, can often result in severe injuries.

In order to decrease the manufacturer’s relative fault, the defense may also argue that the vehicle was being operated recklessly, that the driver was traveling too fast for conditions, or that the driver overreacted to a particular situation. Human factors testimony can counter this type of argument by showing that the driver reacted reasonably under the sudden circumstances of the particular accident.


In addition to the usual cast of experts in an automotive crashworthiness case, consideration should be given to less frequently utilized areas of expertise which are occasionally needed. These are the various specialties that one does not ordinarily think of until receiving the adversary’s expert designation.

One such expert is a forensic toxicologist. In many serious injury accidents a driver is under the influence of alcohol and the defense will normally want to place as much comparative fault on the driver as possible, by arguing alcohol was a contributing cause of the collision. (49 C.F.R. 571.208 (1993)) A forensic toxicologist can address this issue and determine the validity of blood alcohol readings, as well as the degree of impairment to the driver’s ability to perceive and react.

Automotive crashworthiness cases often involve serious brain injuries. If the cause of the injury is in dispute, a neurologist may be needed in addition to a biomechanics expert and a radiologist. For example, if there are multiple blows or injuries to the plaintiff’s head, there may be an issue as to which caused the major brain injury. While the radiologist can identify injured areas of the head and abnormalities on the x-rays and CT’s, a neurologist can assist in determining the injured area of the brain which resulted in permanent impairment, and the cause of the injury, based on physical manifestations and symptoms during plaintiff’s initial treatment.

Another expert which may be needed is a forensic pathologist. If there is a question about where the plaintiff’s body came in contact with the interior of the vehicle, it may be helpful to obtain an analysis of debris found on seatbelts, dashboards, and headliners. Sometimes, a microscopic analysis of dents or scuff marks in these areas reveals evidence of skin, blood or hair.

In fuel system crashworthiness cases involving post-collision fires, the defense will sometimes retain experts in fire cause and origin, to attempt to reconstruct the progress of the fire. This is done to attribute the majority of fuel leakage to sources other than those caused by obvious defects such as sharp components in close proximity to the fuel tank.

If the vehicle has been in a prior collision and repaired, which is not an infrequent occurrence, the defense will contend that the prior damage weakened or diminished the ability of the vehicle to withstand the second accident. Some manufacturers have even moved for summary judgment, arguing that this is a significant modification and an unforeseeable misuse. To counter this defense, it may be advisable to retain an auto body repair expert to testify regarding the extent of repair work and its actual effect on the vehicle’s structure.


In an automotive crashworthiness case, selecting experts should be an ongoing process. As new theories are developed and new issues arise or new defenses are raised, the plaintiff’s attorney should identify areas where expert testimony will be needed to prove the case.

The experts selected should complement each other without being cumulative, and they should provide mutual support without surrendering their independence. Most of all, the sum and scope of their expertise should cover all bases without forcing an individual expert to stray beyond established areas of expertise. (Butkowski v. General Motors Corp, 497 F.2d 1158, 1159 (2nd Cir. 1974)); Perkins v. Volkswagen of America, Inc., 596 F.2d 681, 682 (5th Cir. 1979)) Selecting the right combination of experts does not guarantee the success of a case, but it will improve the odds considerably.