Pseudoscience in forensic practice

DEFINITION: Use in forensic settings of disciplines that possess the superficial appearance of science but lack its substance.

SIGNIFICANCE: On a daily basis, law-enforcement officials confront a host of challenges that often force them to make critical decisions under extreme time pressure and highly stressful circumstances. These decisions involve complex questions of innocence versus guilt, the profiling of criminal suspects, lie detection, the validity of eyewitness testimony, and the interpretation of crime scene evidence, to name just a few. The accuracy of such techniques has the potential to determine crucial life-changing decisions, even capital punishment. As in many professions, individuals in law enforcement must evaluate techniques with a critical eye before using them. Like all disciplines that interpret data to make real-world decisions, forensic science can easily fall prey to the seductive charms of pseudoscience

Given the challenges of law-enforcement investigations, it is not surprising that forensic scientists have turned to psychology for assistance in evaluating the scientific support for the techniques they use. In the 1870s, Francis Galton, a cousin of Charles Darwin, experimented with a word-association test (in which a test examiner says a word, such as “money,” and waits for a response from the subject) as a tool for lie detection. In the early twentieth century, Hugo Münsterberg performed experiments that demonstrated the fallibility of eyewitness testimony. Since that time, psychological researchers have spearheaded the development of scientifically grounded procedures to enhance the accuracy of forensic techniques. Nevertheless, the field of law enforcement continues to grapple with the pressing task of discriminating legitimate from illegitimate practices.

Central Characteristics of Pseudoscience

Pseudoscience differs from bona fide science in that pseudoscience does not “play by the rules” of science, even though it mimics some of the outward features of science. Philosopher of science Mario Bunge has suggested the categories of “research fields” and “belief fields” to distinguish science from pseudoscience, arguing that scientific practices are distinguished by scientific support as opposed to intuition or faith. For instance, experience alone is not sufficient for officers to believe that their procedures produce accurate confessions; these procedures must be validated by scientific evidence.

In a scientific discipline, data must be reproducible—that is, replicable—across multiple studies, ideally studies conducted by independent investigators. In addition, most sciences display connectivity, meaning that they build on previous findings in a cumulative fashion. In contrast, most pseudosciences lack replicability and connectivity.

Science and pseudoscience are not always easy to distinguish, because they lie at opposite ends of a continuum, differing in degree rather than in kind. Nevertheless, a number of indicators can help locate practices, including those used in forensic settings, on the fuzzy spectrum between science and pseudoscience. Seven especially crucial indicators are described below.

Lack of Falsifiability and Overuse of Ad Hoc Maneuvers

Philosopher of science Karl Raimund Popper proposed that falsifiability is the key criterion distinguishing science from nonscience—that is, scientific claims can be shown to be wrong if exists to contradict them. Statements such as “God created the universe” may be true or false, but they are not falsifiable using scientific methods because they cannot be refuted with observable evidence. As Popper observed, when research generates findings that seemingly falsify a given claim, pseudosciences often invoke ad hoc maneuvers—that is, escape hatches or loopholes—to explain away these negative findings.

In the case of fingerprint analysis, for example, some proponents claim an accuracy rate as high as 99.9 percent. They assert that a given fingerprint can be perfectly matched to an exemplar print, to the exclusion of all other possible sources of that print. When the technique fails, they often point to such special circumstances as distorted or insufficient prints or misuse of a fingerprint apparatus to explain why the findings did not support the claims. The repeated use of such ad hoc explanations after the fact to explain away negative findings renders a good deal of fingerprint analysis more pseudoscientific than scientific. In some cases, the limited use of ad hoc explanations can provide directions for future research, but pseudosciences invoke such explanations more often than not, rendering their claims virtually unfalsifiable.

Evasion of Peer Review

Mature sciences rely on a procedure called peer review as a safeguard against error. In peer review, submitted journal articles that evaluate scientific claims are read by outside experts (at least one, and typically three or more) who are entrusted with the task of subjecting the work to relatively impartial scrutiny. In many cases, the peer-review process results in outright rejection of articles; in others, articles are either rejected with an invitation to resubmit following substantial revisions or accepted provisionally.

Peer review is not a perfect filter against poor-quality research, but it is often an essential safeguard. Many pseudosciences bypass this safeguard, preferring to evaluate claims on their own. For example, graphology, the examination of handwriting to infer personality characteristics (not to be confused with forensic handwriting examination or analysis), has been used to profile child molesters and sadistic criminals although virtually no evidence exists to support the validity of this technique. Different and often contradictory schools of graphology have continued in isolation for centuries, ignoring the extensive scientific evidence that shows graphology to be an invalid means of assessing personality characteristics. Despite the overwhelming scientific literature debunking their claims, most graphology proponents continue to advance strong assertions without the restraint and objectivity afforded by the peer-review process.

Lack of Self-Correction

In the long run, science is self-correcting: Incorrect claims tend to be revised or weeded out, whereas correct claims tend to survive. In contrast, in pseudosciences, faulty claims tend to persist for lengthy periods of time, resulting in intellectual stagnation. For example, so-called truth serums are drugs, typically barbiturates, that supposedly elicit truthful information from reluctant individuals. Research has shown, however, that such drugs work in much the same way alcoholic beverages do: They reduce people’s inhibitions, making them more likely to disclose both false and true information. The continued use of truth serums to elicit confessions and to unearth supposedly buried memories despite contrary evidence illustrates a lack of self-correction.

Bite-mark analysis was accepted in the judicial system in the 1970s despite any studies showing it to be accurate. Expert witnesses vouched for the practice, though they had no research to back it up, but once it had been accepted, it set legal precedent. After more than two dozen people were wrongly convicted based on bite-mark analysis, researchers rejected the practice in the early twenty-first century. However, as of 2024, some courts continued to accept expert testimony on the subject.

Confirmation Bias

Some psychologists, such as Carol Tavris, have argued that the scientific method is a safeguard against confirmation bias—the tendency of human beings to seek out evidence that supports their own hypotheses while ignoring, minimizing, or distorting evidence that does not. Most pseudosciences lack protections against confirmation bias. For example, the interrogation process used by many law-enforcement investigators lacks this safeguard. Investigators often form conclusions about a target prior to obtaining sound evidence, and the process of interrogation may become more about confirming those conclusions than about obtaining impartial information. Such presumptions can lead interrogators to close their minds toward alternative hypotheses and make them likely to seek out support selectively for their beliefs.

Research has shown that the presumption of guilt can influence investigators to adopt an interrogation style that elicits guilty behavior from suspects. Saul M. Kassin and Gisli Gudjonsson have described how suspicion of guilt on the part of interrogators can shape their behavior and lead suspects to act anxiously or defensively, thereby inadvertently confirming the interrogators’ suspicions. If questioners increase their bodily movement during an interrogation, the suspect is likely to mimic them and in turn appear nervous and “guilty.” As with any belief, interrogators’ confidence in their beliefs or “hunches” that they are right about suspects can make it difficult for them to attend to data that do not support their beliefs.

Overreliance on Testimonial and Anecdotal Evidence

Informal testimonials and anecdotes suggesting that a technique is effective can sometimes provide justification for investigating that technique further in systematic studies, but they are never sufficient for concluding that a technique is effective. Many pseudosciences rely on informal personal evidence to validate their claims. For example, in more than 75 percent of cases in which postconviction analysis of (deoxyribonucleic acid) evidence has demonstrated that the convictions were in error, eyewitness misidentification was a primary cause of the initial guilty verdicts. In such cases, law-enforcement officials relied too heavily on anecdotal for proof of guilt. Individuals’ subjective experiences are neither recorded nor preserved in memory exactly as the events occurred, and recollections can be contaminated at many steps between the witnessing of an event and the relayed testimony given at the police station or in the courtroom.

Extravagant Claims

Good scientists are aware that their claims are almost always provisional and might be overturned by later evidence; they are also careful not to overstate assertions in the absence of compelling evidence. In contrast, advocates of pseudoscience frequently advance extreme claims that greatly outstrip scientific evidence.

For example, some proponents of the or “lie detector” test make excessive claims regarding the accuracy of the device in detecting lies, asserting an accuracy rate of close to 100 percent. However, as psychologist David T. Lykken has observed, voluminous evidence suggests that polygraphs probably perform better than chance but are nowhere near as accurate as promoters claim. Because they measure physiological arousal rather than lying per se, they are especially prone to mislabeling innocent subjects as guilty. As with any tool or method, such extravagant claims should be seen as indicators that proponents of a given practice have overstated its ability and that the practice is operating outside the bounds of good science.

Ad Antequitem Fallacy

As the history of science shows, claims that have been around for a long time are not necessarily correct. For example, even though the practice of astrology is more than thirty-five hundred years old, there is no scientific support for astrologers’ claims. Many pseudosciences fall prey to the ad antequitem fallacy: the error of concluding that because a claim is old, it must be valid. For example, hair comparison and blood type matching have been relied on in criminal cases since the nineteenth century, but the use of these techniques is based on relatively scant scientific validation. Scientific research has exposed these practices as lacking in specificity in identifying given individuals as having been present at crime scenes.

By keeping the indicators described above in mind, consumers of the forensic literature, including jurors, lawyers, judges, and police officers, can better distinguish science from pseudoscience. Moreover, knowledge of such indicators may help to bridge the wide gap between the law-enforcement and scientific communities and help ensure that forensic practices are based on solid research evidence.

Bibliography

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