Don't fall for defense fallacies.

In crash injury cases, defense experts often impress jurors with seemingly reasonable testimony. Expose their logical fallacies to discredit their conclusions.

The most common method used by defense experts to gain jurors' confidence in crash injury cases is to present opinion-based testimony as scientific fact. This allows the expert to sidestep the medical opinion of the plaintiff's treating physician and gives jurors permission to disregard the physician's opinion on the ground that he or she is poorly informed on the subject of crash injury science.

One of the primary differences between treating physician testimony and defense expert testimony is that the physician describes his or her findings and offers an opinion supported by training and experience. Although clinical judgment may be based in logical thought, the physician is typically not accustomed to explaining his or her thought processes in a way that will appeal to laypeople.

The defense expert, on the other hand, who jurors know does not have a doctor-patient relationship with the plaintiff, will look for ways to present the logic or common sense of his or her opinion. Otherwise, jurors might be inclined to believe the expert is motivated only by a paycheck from the defense attorney.

Defense experts who typically use this technique include accident reconstructionists and biomechanical engineers who state that the plaintiff "should not" have been injured in the crash because it generated insufficient force to cause injury. In this way, the defense expert does not have to know anything about the plaintiff; rather, the expert implies knowledge about all other crash victims, who, presumably, were not injured in similar crashes.

The jury is left with the notion that the plaintiff is either the most injury-prone person in the world or a liar. The second choice is frequently more appealing to jurors than the first for a variety of reasons that have been evaluated at length.(1)

This article explores the seemingly logical bases for defense experts' specious conclusions. The apparent logic of the opinion fools jurors into believing the testimony, even when it is contradicted by the opinion of a well-qualified physician with extensive experience with the plaintiff. The defense expert's opinion appears to provide insight into the facts of the case but does not actually apply directly to those facts.

The expert is able to accomplish this trick by using logical fallacy as a rhetorical tool. A logical fallacy is an argument that gives a reason in support of a conclusion when the reason does not, in fact, support the conclusion.

At the heart of almost all these specious defense opinions is a misuse of epidemiologic concepts, so some knowledge, or at least an awareness, of epidemiology is essential for understanding many proofs of the fallacies. "Epidemiology" is loosely defined as the study of the occurrence of disease and injury in populations. When an expert says an injury "should not" have occurred in a given crash, the expert is stating an inferred knowledge of all outcomes of similar crashes--knowledge that can only be gained through epidemiologic study.

The epidemiologist makes an observation-for example, a study of rear-impact collisions in 37 states shows that 50 percent of women are injured in crashes with less than $1,000 of vehicle damage, and 23 percent are injured in crashes with less than $500 in damage? The biomechanical engineer, on the other hand, devises an experimental study to understand the observation--for example, high-speed cineradiography (motion picture X-ray) of human volunteer crash testing shows that the lower cervical spine hyperextends in a low-speed rear-impact collision before the head strikes the head restraint,(3) potentially accounting for the injuries seen in low-speed crashes.

An inappropriate use of the biomechanical literature would be to conclude that because the volunteers in the cineradiography study were not significantly injured, the observed injuries in the epidemiological study were not real.

Critical thinking, a necessary skill for an effective judge or juror, requires that alternatives be explored before a single explanation for an observed phenomenon is accepted. To expose the defense expert's logical fallacies, the plaintiff attorney and expert must explain why a person can be significantly injured in a low-speed crash.

The logical fallacies commonly seen in specious defense testimony fall into the following seven major categories.

Fallacies of distraction

These fallacies are intended to distract jurors' attention from the lack of a reliable basis for the assertion. Some are used by defense counsel in cross-examination or summation. [See the sidebar accompanying this article.] Others, including the "false dilemma," are used by defense experts.

In the false dilemma fallacy, a limited number of options is given, while in reality there are more options. A hallmark of this fallacy is the improper use of the word "or."

Example: A crash will either produce significant damage and cause injury, or it will produce little or no damage and cause no injury. In the crash at issue, there was no damage, so no injury was possible.

Proof of the fallacy: Point out that crashes with little or no damage can and do cause injury. One study of rear-impact crashes in 37 states showed that 23 percent of women and 18 percent of men are injured in crashes with less than $500 in vehicle damage.(4) Another study reported on 237 subjects who were injured in rear-impact crashes with little or no vehicle damage. Forty-six percent of the group suffered neck and lower back injuries, and 21 percent had neck and arm complaints.(5) Other researchers reported that 80 percent of rear-impact injuries they studied occurred at impact speeds below 13 mph.(6)

Fallacies of authority

These fallacies focus on the person making the argument instead of discussing reasons to believe or disbelieve the conclusion.

Appeal to authority. An appeal to authority is inappropriate when the expert offering the opinion is not qualified to give an opinion on the subject. This fallacy is most often seen when defense medical or biomechanical experts offer opinions regarding epidemiologic issues.

Example: The defense neurosurgeon testifies that the crash could not have caused the plaintiff's cervical disk herniation, based on the defense biomechanical engineer's opinion that the force generated in the crash was insufficient to cause the injury.

Proof of the fallacy: Identify the opinion as epidemiologic rather than medical or biomechanical. This can be tricky when the opinion sounds biomechanical, as in the example. A biomechanical opinion, however, would be to state that a disk can herniate when subjected to 10 foot-pounds of force. The opinion becomes epidemiologic when the expert states that a disk never herniates when subjected to 10 footpounds of force, as this inference regards the entire population.

Anonymous authorities. The authority being cited is not named. This fallacy is often seen in defense biomechanical reports and in medical reports and testimony, which use vague wording like "studies show ... "and "it has been frequently shown in the medical literature.... "

Example: The plaintiff has symptoms of a closed head injury, yet it is well established that these injuries do not occur in crashes with less than 70g of acceleration, and the subject crash had only 2g of acceleration.

Proof of the fallacy: Question the expert about the source of the authority. If the expert gives the source, show its scientific flaws. In the example, the unnamed source is a study of experimentally induced brain hemorrhages in ferrets.(7) If the expert cannot or will not name the source, have the testimony stricken as speculative.

Fallacies of induction

Inductive reasoning infers from the properties of a sample to the properties of a population as a whole--in other words, it draws conclusions about a large group based on information obtained from a small group.

Even without any expertise in statistics, most people understand the fallacy of, for example, taking the weight of a single randomly selected person as an accurate measure of the average weight of all people. The flaws in this reasoning are obvious because random variation dictates an inherent variability in the population. A sample that is too small may contain the most extreme values in a population. The most important characteristic of a sample is that it faithfully represent the qualities of the population from which it is drawn and to which its characteristics will be generalized.

Hasty generalization. The sample size is too small to support the conclusion.

Example: Five people in the crash test weren't injured, so no one should ever be injured.

Proof of the fallacy: Identify the size of the sample and the population to which the inference is applied. Then demonstrate that the sample size is too small to encompass the wide variability of human responses to trauma.(8)

Unrepresentative sample. The sample used in an inductive inference is significantly different from the population for which the inference is intended.

Example: Human volunteer crash tests involving similar speeds have never produced a significant or chronic injury, so the plaintiff's significant, chronic injury is unlikely to be related to the crash.

Proof of the fallacy: Show how the sample is different from the population as a whole and the plaintiff in particular. The characteristics of the crash test population (for example, male, healthy, prepared for the collision) can be compared to the pariculars of the plaintiff's crash.(9)

False analogy. The expert presents two events as being similar and claims that because one event has a particular property, it can be inferred that the other event has the same property.

Example: The subject crash was reconstructed to show that the plaintiff sustained 6g of peak head acceleration. A peer-reviewed publication has shown that simply "plopping in a chair" generates greater force on the head than the crash did, yet no injury is ever expected to be caused by plopping in a chair. Thus, the plaintiff could not have been hurt in the crash.

Proof of the fallacy: Identify the two events being compared and the property being ascribed to both. Show that the two events are different in a way that will affect whether they both have the property.

In the example, plopping in a chair is a controlled movement that does not produce differences in acceleration between the head and torso. In contrast, a motor vehicle crash causes uncontrolled movement that produces significant differences in acceleration, and thus shear force (force created when two body parts are moved in opposite directions), between the head and torso. One study compared the acceleration impulse (the duration of acceleration multiplied by its magnitude) of an average low-speed rear-impact crash to that of plopping in a chair and found that the crash generates an impulse 200 times greater than the plop.(10)

Exclusion of evidence. Important evidence that would undermine an inductive argument is excluded from consideration.

Example: In a report of a defense medical exam, the expert states that there is no objective indication of injury and concludes the plaintiff has not suffered any permanent harm as a result of the crash.

Proof of the fallacy: Present the missing evidence and show how it would change the expert's conclusions. In some cases, the defense medical expert includes significant examination findings in the report but ignores them when drawing conclusions. In other cases, some findings--such as complaints of pain with limited range of motion-are left out of the report.

Often, the report includes irrelevant findings and overlooks essential measures of function in other areas. It is important to understand the findings that prove the plaintiff's injuries to use them when cross-examining the defense witness regarding his or her examination methods.

Fallacy of generalization

A generalization is a statement that may be true part of the time, but not always. Defense experts in crash injury cases often testify that "it is highly unlikely" or "nearly impossible" that injury would occur in the plaintiff's crash. These statements imply epidemiologic knowledge that is either incorrect or unknown, and the expert may not be qualified to infer the conclusion from existing data.

Example: Most people are not injured when they are in a crash involving a change in velocity of less than 6 mph. It is highly unlikely that the plaintiff was injured in the subject crash, which involved a 5 mph change in velocity.

Proof of the fallacy: Identify the generalization and show that it is not always true. Then demonstrate that the plaintiff's medical condition suggests that the generalization should not apply. The studies cited above show that injuries do occur in some cases,(11) and other research shows that even serious injury can occur at low accelerations.(12) A biomechanical engineer is not qualified to determine whether the case is an exception to the generalization because this opinion would be medical testimony regarding the plaintiff's condition. Therefore, the expert may not be allowed to testify on the subject.

Fallacies of causation

People often conclude that one thing causes another. But the relation between cause and effect is complex, particularly with regard to crash-related injuries. Many injuries associated with trauma, such as cervical disk herniation, can occur in a number of different ways. For example, a rotator cuff tear can occur as a result of a crash, but it is more often associated with age-related changes in the shoulder.

The causal fallacy of "coincidental correlation" is common in crash injury defense. An assumption is made that because one event follows another, the second event must have been caused by the first. Typically, a defense expert assumes that an injury must have occurred in a traumatic incident other than the crash.

Example: The plaintiff sought treatment for neck pain in the month before the crash, so all of his or her current symptoms are related to the precrash incident.

Proof of the fallacy: Show that the correlation is coincidental by demonstrating that the injury would have occurred even if the precrash incident had not. The medical records help establish the difference between the precrash and postcrash condition. Proof of a neck condition before the crash is not proof that the current condition predated the crash.

Fallacy of irrelevant conclusion

In this fallacy, the expert misses the point of the disputed issue. His or her argument purports to prove one thing but instead proves a different conclusion.

Example: The plaintiff claims a neck injury, but head restraints prevent hyperextension of the neck. The vehicle was equipped with a head restraint, so the crash could not have caused the injury.

Proof of the fallacy: Show that the expert's conclusion is not the one that the expert set out to prove. Here, the expert proved that the plaintiff's neck did not hyperextend but not that it was not injured.

Fallacy of the parts versus the whole

In this fallacy, the expert mistakenly assumes that the whole is nothing more than the sum of its parts. However, things joined together may have different properties as a whole than they do separately. Experts using this fallacy argue that if A occurs, then B occurs, and if A does not occur, then neither does B.

Example: Fracture and dislocation of the cervical spine rarely occur without disk herniation. The plaintiff does not have a fracture and dislocation, so he could not have herniated a cervical disk in the crash.

Proof of the fallacy: Show that even though the premise may be true, the conclusion is false. In particular, show that the consequence B may occur even though event A does not occur. In the example, show that although more than 90 percent of cervical fractures and dislocations also include disk herniations, 99 percent of cervical disk herniations do not include a fracture and dislocation, as these conditions are not prerequisites for herniation.

Any attorney who handles auto cases, especially those involving low-speed collisions, is likely to encounter at least some of these arguments at trial. To successfully counter the questionable science and semantic trickery frequently used by the defense, the attorney must be able to readily recognize the logical fallacies described here.

Considering options

Critical thinking requires that alternatives be explored before a single explanation for an observed phenomenon is accepted.

Notes

(1.) See, e.g., Valerie P. Hans, What Jurors Think About Connective Tissue Injuries, TRIAL, July 2000, at 18.

(2.) CHARLES M. FARMER ET AL., RELATIONSHIP OF HEAD RESTRAINT POSITIONING TO DRIVER NECK INJURY IN REAR-END CRASHES (Ins. Inst. for Highway Safety 1998).

(3.) Koji Kaneoka et al.,Motion Analysis of Cervical Vertebrae During Whiplash Loading, 24 SPINE 763 (1999).

(4.) FARMER ET AL.,supra note 2.

(5.) Allan F. Tencer & Sohlail K. Mirza, Is There a Relationship Between Pre-existing Spinal Degeneration and Whiplash-Associated Symptoms in Victims of Rear-end Auto Impacts? Cervical Spine Research Society 27th Annual Meeting (Dec. 16-18, 1999).

(6.) I. Olsson et al.,An In-depth Study of Neck Injuries in Rear-end Collisions, 1990 INT'L RES. COUNCIL ON THE BIOMECHANICS OF IMPACT CONF. 1.

(7.) David C. Viano et al., Biomechanics of Brain and Spinal Cord Injury: Analysis of Neuropathologic and Neurophysiologic Experiments, 1 J. CRASH PREVENTION & INJURY 35 (1999).

(8.) For a more thorough discussion of this fallacy, see Michael D. Freeman et al.,A Review and Methodologic Critique of the Literature Refuting Whiplash Syndrome, 24 SPINE 86 (1999).

(9.) See id.

(10.) See id. at 96.

(11.) See, e.g., FARMER ET AL., supra note 2; Tencer & Mirza, supra note 5.

(12.) Michael D. Freeman et al., Serious Spinal Injury Resulting from Low-level Accelerations: A Study of Roller Coaster Injuries (on file with author).

RELATED ARTICLE: Fallacies defense attorneys use

Experts aren't the only ones who use logical fallacies in auto cases. Here are a few that defense attorneys may trot out in cross-examination of plaintiff experts or during summation.

Appeal to consequences. The attorney points to the disagreeable consequences of holding a particular belief to show that the belief is false. This fallacy is essentially a threat.

Example: If the jurors awards this plaintiff money for this "little fender bender," they are contributing to the abuse of the legal system.

Proof of the fallacy: Identify the consequences alluded to by counsel (as well as the language intended to minimize the seriousness of the injury) and point out the differences between the current case and one that would legitimately be viewed as an abuse of the system. Point out that your client's case involves a real injury and reasonable medical costs.

Appeal to popularity. A proposition is held to be true because it is widely believed by some sector of the population. This fallacy is sometimes also called the "appeal to emotion" because emotional appeals often sway the population as a whole. It can also be formulated as a call to common sense. It calls for the jurors to speculate regarding factual issues.

Example: It is common sense that you can't get hurt in a no-damage crash, and photos of the vehicles show there was no damage in the collision.

Proof of the fallacy: Either present evidence that shows the argument is untrue or prevent the defense from making the argument because it calls for the jury to speculate. The fact that 23 percent of women and 18 percent of men are injured in rear-impact crashes with less than $500 in damage proves the fallacy. (Charles M. Farmer et al., Relationship of Head Restraint Positioning to Driver Neck Injury in Rear-end Crashes, Insurance Institute for Highway Safety (Sept. 1998).) In several cases, photos showing no damage to vehicles have been kept out of trials because they call for jurors to speculate that there is a relationship between vehicle damage and injury.

Attack on the plaintiff expert. Defense attorneys frequently use this fallacy when dealing with plaintiff testimony from a chiropractic physician.

Example: Defense counsel asks the chiropractor whether he or she performs surgery, prescribes medication, or has hospital privileges, aware that the expert will answer "no." The clear implication is that the expert is unqualified, in contrast to the defense expert, a board-certified neurosurgeon.

Proof of the fallacy: Point out this attack to the jury and show that the chiropractor has more experience and training for diagnosis and treatment of the plaintiff's injuries than the defense expert does, and considerably more experience with the plaintiff. Also, explain that the very characteristic that the defense cites as a strength of its expert-qualification as a neurosurgeon--is useless because the medical issues at hand are not neurosurgical.

Straw man. Typically used by defense counsel in cross-examining the plaintiff's expert, this fallacy consists of an attack on a position that the plaintiff has not actually taken.

Example: Defense counsel asks, "Doctor, are you saying that every person who is in a little fender bender will end up with neck surgery?"

Proof of the fallacy: Demonstrate that the doctor's argument has been misrepresented and describe his or her true, stronger argument. In the example, the witness would answer, "I am not commenting on what occurs in other crashes to other individuals; rather, I am confining my comments to the injuriousness of the subject crash and the injury susceptibility of the plaintiff."

Michael D. Freeman is a forensic trauma epidemiologist in the Department of Public Health and Preventive Medicine at the Oregon Health Sciences University School of Medicine in Portland. He can be reached by e-mail at drmfreeman@ earthlink.net.