Behavioral Science Evidence in Criminal Trials Research Paper

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Expert witnesses are by no means always scientists, but they must know something the judge or jury do not. The judge will decide whether or not that is the case. For the behavioral sciences, this approach tends to favor the clinical end of the spectrum; even there, however, lawyers have been known to be skeptical of the value of such evidence in a criminal trial. Such reservations are often founded on ignorance of the culture, purpose, and circumstances that form the background against which experts make behavioral assessments. Courts should be aware of the requirements of diagnoses for clinical purposes. The length of observation period normally necessary for diagnostic purposes is unlikely to be available in the context of preparation for trial. A relatively short period of contact possibly makes it easier for a mental illness to be faked. In any event, a retrospective analysis of how an observed condition would have affected past events inevitably involves much speculation.

Behavioral sciences such as psychology, sociology, or anthropology do not fit comfortably within conventional perceptions of expert scientific evidence. There is, within these disciplines, extensive disagreement about questions of central importance, such as methodology. This makes it more difficult to persuade judges that witnesses specializing in these areas of scholarship have an expert opinion of evidential value. Even more problematically, to some extent behavioral sciences represent a challenge to the power of a tribunal of fact, whether judge, juror, or magistrate, to determine the ultimate issue, the matter to be determined in reaching a verdict. Frequently the central or ultimate issue in a criminal trial requires a determination of how an individual, often the defendant or victim, responded to a particular situation. This decision by the trier of fact tends to be based to some extent on intuitive or heuristic judgments about human behavior. Many lawyers would defend such decision-making as an essential element in the role of the lay jury as the representative of popular sentiment, bringing community moral and practical judgments into the criminal court. This role, and the way in which it has traditionally been performed, insofar as it consists of assessments of human reactions and motivations, occupies the very area of expertise claimed by behavioral science. Unlike “hard science,” therefore, where courts defer to specialist knowledge, behavioral science is seen as trespassing on the fundamentals of the jury’s responsibility and rationale. Lay finders of fact and behavioral experts are effectively pitted in competition against each other in terms of their ability to understand and evaluate human nature.

Admissibility Of Behavioral Science Evidence

Where a potential witness can contribute expertise indubitably outside the experience of the tribunal of fact, such as a psychiatrist or clinical psychologist in relation to the defenses of diminished responsibility or insanity, the expert may, even in jurisdictions which prohibit expert opinion on the ultimate issue, give evidence as to the presence or absence and nature of the condition in question and whether it satisfies legal requirements. In most cases, however, behavioral science evidence occupies a problematic middle ground between acknowledged scientific expertise, such as clinical diagnosis, and the kind of “common sense” or everyday perceptions and generalizations of human behavior that are considered properly to be the province of the jury. Given that, essentially, the common law approach to the admissibility of expert opinion evidence is one of laissez-faire insofar as the question is left to the trial judge in the particular proceedings (Roberts and Zuckerman 2010, pp. 482–493), the admissibility of behavioral science evidence is determined on a case-by-case basis. However, courts are jealously protective of the role of the finder of fact as the arbiter of everyday life. In the Court of Appeal of England and Wales, Lord Justice Lawton famously observed:

The fact that an expert witness has impressive scientific qualifications does not by that fact alone make his opinion on matters of human nature and behaviour within the limits of normality any more helpful than that of the jurors themselves; but there is a danger that they may think that it does….Jurors do not need psychiatrists to tell them how ordinary folk who are not suffering from any mental illness are likely to react to the stresses and strains of life. (R v Turner [1975] 1 All ER 70, 74)

A concern to protect the role of the jury in interpreting events and applying their own standards of reasonableness may prompt courts to distinguish “normal” behavior, preempting expert opinion evidence, from “abnormal” mental states. This sharp distinction is a legal invention. In psychiatry, the difference is a matter of degree rather than kind, and as medical knowledge advances, the blurry line between them shifts over time. “Medical expertise lies along a line between the predictive technological know-how of the physical science and the loose generalizations of social science practice” (Smith 1985, p. 69). Nevertheless, legal jurisdictions may develop their own typologies of mental states indicating which will be deemed pathological or normal as far as the law of that jurisdiction is concerned. This will determine whether the jury require expert help to decide what the effect of the disorder might have been. And, while psychological research on memory in “normal” adults would be generally excluded from evidence, child development will usually be regarded as an established scientific discipline upon which a specialist could assist the court. Explaining developmental aspects of children’s memories and how a particular child compares with the norm does not usurp the function of the jury, as long as the expert does not say that a particular child is telling the truth; that would be for the court to decide.

As “gate-keepers” determining whether or not particular expert evidence is admissible in a given case, judges arbitrate between areas of psychology in which it is possible to draw on specialist expertise over and above the everyday experiences of lay jurors. Obscure or recently identified conditions are more likely than familiar ones to be regarded with hostility. The judge has to accept both that the claimed expertise exists as a discipline and that the particular witness is sufficiently acquainted with it. A second aspect of the “gate-keeper” role is the possibility that the judge will exercise some kind of reliability standard in deciding whether or not the opinion evidence should be admitted. In England and Wales, however, there has been concern that a “culture of acceptance” of purportedly scientific evidence could be creating miscarriages of justice. A generous approach is likely to be founded on the belief that cross-examination by opponents is an effective tool to unmask any bogus science or scientist. True, the anxiety in England and Wales about “junk science” expressed in recent case law, the academic literature, and a significant official report (Law Commission 2011) has arisen in the context of “hard,” nonbehavioral scientific evidence on such matters as the reliability of “earprint” evidence (R v Dallagher [2002] EWCA Crim 1903), or shaken baby syndrome (R v Harris [2006] 1 Cr App R 5, [2005] EWCA Crim 1980). However, the Law Commission’s recommendations for an explicit reliability standard to regulate the admission of all expert opinion evidence in criminal proceedings would, if implemented, apply to “soft” science, too. This approach has caused problems in the United States, where judicial attempts to evolve a workable reliability test have been accused of favoring dated theories and militating against the admission of reliable and pertinent behavioral science evidence.

Defining Reliability Standards

An influential reliability test, deriving from Frye v US, 293 F 1013 (DC Cir 1923), is that the discipline commands “general acceptability to the scientific community.” A general acceptance criterion could be thought to discriminate against any developing science, and is likely to exclude any discipline where there is substantial controversy among practitioners. An Australian test, inquiring “whether the subject matter of the [expert’s] opinion forms part of a body of knowledge or experience which is sufficiently organized or recognized to be accepted as a reliable body of knowledge or experience” (R v Bonython (1984) 38 SASR 45) is along similar lines. The alternative American test, advocated by Daubert v Merrell Dow Pharmaceuticals, 113 S Ct 2786 (1993), aims to enable the courts to be more responsive to scientific innovation, while at the same time demanding that sufficient reliability is demonstrated. Trial judges are enjoined by Daubert to consider factors such as whether the technique in question has been subjected to peer review, whether it has been generally accepted, and whether the theory or technique can be or has been tested. Another factor that may be considered is the falsifiability of the opinion, which means that its plausibility depends upon whether the theory or concept on which it rests is capable of being shown to be false. Any proposition incapable of being verified in this way should, on the Daubert test, be treated with great suspicion by the courts.

The difficulty for the social and behavioral sciences, economics, sociology, and psychology, is that they do not fit easily into this portrait of a body of knowledge consisting of a set of propositions which have been demonstrated to hold in all circumstances. The English Law Commission proposes a new test for reliability which would force judges to decide whether or not the purported science is soundly based. Trial judges should consider a number of factors in making this judgment, the most significant for behavioral science being: whether or not any relevant hypothesis has been sufficiently scrutinized, the nature of the data on which the opinion is based, where the expert’s opinion relies on the results of any measurement or survey, and whether the opinion takes proper account of matters such as the degree of precision or margin of uncertainty in data collection (Law Commission 2011).

Reliability Standards And Behavioral Science Evidence

Evidence given by experts in behavioral or social sciences is not easily accommodated within a Daubert-style test for admissibility. Falsifiability is not an appropriate technique in the social sciences. Controlled experiments are virtually impossible: “we correctly refuse to abuse a child for the sake of research” (Graham 1998). Aware of such practical and ethical constraints, many American judges have, sidestepped Daubert on the grounds that the test does not apply to “soft” science. They have proceeded to admit evidence of false confessions and suggestible personalities, post-traumatic stress disorder (PTSD), and repressed memory syndrome (Slovenko 1998). Meanwhile, Canadian courts have allowed expert evidence on “learned helplessness” to be adduced to dispel any jury myths about battered women (see R v Lavallee (1990) 55 CCC (3d) 97).

The reception of “syndrome evidence” has not met with universal approval. For instance, controversy surrounds the reception in rape trials of evidence of rape trauma syndrome. This is offered to demonstrate that the complainant’s behavior is consistent with her allegation that she was raped. Critics suggest that the alleged syndrome is based on inconclusive research and could consequently cause great prejudice to the defendant. It has not been established whether rape trauma syndrome is a subset of posttraumatic stress disorder. It lacks specificity, in that many kinds of behavior appear to fall within its compass; the victim may be afraid to be indoors, or she may be afraid to go out of doors, depending on where the rape took place. Notwithstanding considerable skepticism, evidence of rape trauma syndrome has been admitted in some courts in the United States. Some American judges, however, allow it only as rebuttal evidence after the defense has argued that the complainant’s behavior indicates fabrication. Given the adverse effect on the fact finder where a rape complainant displays no emotion, expert evidence to preempt the complainant’s superficial serenity from being misconstrued may be advisable (Frazier and Borgida 1992). It appears, however, that expert evidence on general aspects of rape trauma syndrome has less impact on a jury than expert testimony linking rape trauma syndrome to specific features of the case (Brekke and Borgida 1988).

It has been argued that courts are being bombarded with an escalating number of novel afflictions, such as “urban survival syndrome,” which could be derided as “trash syndromes.” Over-willingness to accept syndrome evidence could lead to miscarriages of justice (Mosteller 1996). Repressed memory syndrome has been a particular target for criticism; it has been said that according to the falsifiability criterion, claims for repressed memory are not based on valid science. Yet there are psychiatric disorders, such as multiple personality disorder and attention-deficit hyperactivity disorder, listed in professional diagnostic manuals and commanding respect as legitimate medicine, which could equally be said to lack scientific validation (Richardson et al. 1995). One of the problems here is that techniques and theory developed for one purpose are being considered for use in a very different context. Conditions such as child sexual abuse accommodation syndrome or theories of repressed memory, developed originally for therapeutic purposes and therefore characteristically evaluated within their scientific communities in terms of alleviation of symptoms, are being scrutinized by judges for a level of objectively established reliability never sought or claimed for them. Courts which understand this, and mindful of the presumed ability of cross-examination to expose any overstated claim, tend to allow such evidence on the basis that Daubert permits a flexible approach and does not require general acceptance in the scientific community. To apply the Daubert test strictly would deprive fact finders of relevant bodies of knowledge. Yet to abandon any admissibility threshold or critical screening process in relation to expert evidence on behavioral issues would expose courts to the risk that plausible “junk science” would warp decision-making in criminal proceedings.

One might attempt to distinguish evidence presented as scientific knowledge, requiring compliance with Daubert, from specialist knowledge based on experience. The “experiential” category would include, for example, lip-reading expertise (R v Luttrell [2004] 2 Cr App R 31, CA), knowledge of black market drug prices (R v Hodges [2003] 2 Cr App R 247, CA), and handwriting comparisons. In cases involving testimony regarding battered woman syndrome, the evidence would have the beneficial effect of countering potential jury prejudice, but would not be masquerading as proven science. This is, effectively, the pragmatic strategy of many American courts (Renaker 1996). But if “junk science” is to be excluded, judges are left searching for a true test of genuine experience and knowledge. American and British judges appear to have found no alternative, where “soft science” is concerned, to reliance on their own intuitive assessment of the alleged field of expertise. Thus, while an American court may allow evidence of “psychological autopsies,” retrospectively assessing the alleged murder victim’s state of mind and tendency to suicide on the basis of medical records and interviews with family and friends (State v Huber, 62 Ohio Misc.2d 237), English courts remain unpersuaded: R v Gilfoyle [2001] 2 Cr App R 57, CA.

The work of criminal profilers, although heavily featured in film and television drama and, arguably, of use during police investigation, seems to be another area on which judicial opinion is divided – as is the expert community itself. From an objective point of view, psychological profiling seems to be an area of behavioral science far too undeveloped for use in a criminal trial. Profiling does not enjoy universal support among the ranks of psychologists, some of whom regard it as little more than a professional sideline with dubious scientific credentials (Gudjonsson and Copson 2000). It is likely that decision makers who became aware of earlier criminal or other discreditable behavior by an accused person will be readier to convict (Tanford and Penrod 1984; Wagenaar et al. 1993), and so such evidence is particularly problematic when offered as an indicator of guilt as part of the prosecution case (Roberts and Zuckerman 2010, Chap. 14). Conversely, defense profile evidence was excluded from a rape trial on the ground that there was no proof that rapists have particular mental characteristics, or that psychiatrists could, by examination of a person, determine the presence or absence of these supposed characteristics: State v Cavallo, 88 NJ 508; 443 A (2d) 1020, (1982).

Behavioral Science Having Significant Legal Effect

The most well-known area in which the findings of behavioral scientists have influenced criminal trials concerns eyewitness evidence. Where identification is a contested issue in a trial, the ability of an eyewitness to link the accused person to the offense is a potentially invaluable asset to the prosecution. Direct observation by an individual of the perpetrator committing the offense is just about the best evidence that can be presented to the court. The true value of such evidence is, however, in considerable doubt following the findings of psychological experiments testing eyewitness reliability. According to these experimental simulations, accuracy of description varies between 65 % and 75 %, and decreases somewhat over time (Shepherd et al. 1982). Given that most developed legal systems demand prior identification in the relatively clinical conditions furnished by an identification parade before the witness can identify the defendant in court, the more significant data relate to the accuracy of recognition. Here, little reassurance can be offered to criminal lawyers. Although recognizing someone is easier than describing them, the accuracy of recognition is also alarmingly low. Across the multiplicity of studies, it varies between 35 % and 60 %. Although practical difficulties affecting the observation, such as lack of light or a short-lived event affording only a fleeting glimpse, exacerbate the problem, good observation conditions and prolonged observation periods make little difference to overall accuracy. High levels of error in recognition remain.

Identification parades provide only limited safeguards against wrongful identifications. If a parade is held at which the real actor is not present, there is a one-third likelihood of the eyewitness selecting a volunteer (Pigott et al. 1990). It appears that the eyewitness, anxious to choose someone, will select the line-up member who, compared with the other members of the line-up, most resembles the culprit (Wells 1993). If there is a familiar face in the line-up, it may be confused for that of the offender, the witness forgetting the context of a previous acquaintance. This is known as the “transference effect.” Similar mistakes can be made where the person the witness saw resembled someone familiar, such as a well-known TV personality. There are extra layers of unreliability in identifications across races (Shepherd et al. 1974) and, more debatably, across genders and age groups (Jalbert and Getting 1992). In 1984, a black man was convicted of rape in the United States on the basis of an identification by the white female victim, who picked him out from a line-up. In 1995, DNA evidence established that another man had carried out the attack (Memon and McDaid 2000). The witness had been confident of the accuracy of her recognition throughout. Research indicates that eyewitness confidence is no guarantor of accuracy (Deffenbacher and Loftus 1982). The forensic impact of such confidence may be profound, however. Jurors’ common sense presuppositions support the existence of a significant link between witness confidence and accuracy (Wells et al. 2002), and so an eyewitness who insists on the reliability of their memory may exert a very powerful influence on the outcome of the trial.

One way for the problem of eyewitness inaccuracy to be accommodated in a trial setting is to allow an expert witness to explain to the jury that identification evidence may be considerably less reliable than it appears, and to draw attention to any factors in the particular case that would cast doubt on the accuracy of the recognition in question. Uninstructed, jurors seem to be impressed by identification evidence, particularly if there is more than one witness. Judicial warnings apparently do little to moderate juror enthusiasm for eyewitness evidence (Cutler and Penrod 1995), so courts in some US states have attempted to amplify its effect by allowing expert testimony to explain the unreliability of identifications. Whether greater judicial attention should be devoted to the voluminous psychological literature on the accuracy of identification turns partly upon the extent to which it is possible to extrapolate directly from laboratory findings to real-life situations. In one naturalistic study, eyewitnesses interviewed following an armed robbery and fatal shooting in the street achieved strikingly high rates of accuracy. In follow-up interviews, accuracy did not decrease, but new information, also accurate, was offered. The recall of those who suffered the most stress was not adversely affected by their trauma (Yuille and Cutshall 1986). In any event, it would be unwise to dismiss all eyewitness evidence as equally unreliable. Certain individuals may have a good track record for recognition (Cutler and Penrod 1995). It is possibly misleading to claim that eyewitness confidence is no indicator of accuracy whatsoever, since the issue may be more complicated than some research literature allows. Eyewitnesses may legitimately feel confident about the accuracy of some of the details they recall while being less confident about others (Stephenson 1984). Also, there is a significant difference between a confident delivery and actually believing that one’s identification is undoubtedly correct (King 1986). However, most of the relevant research focuses on subjects’ beliefs in the correctness of their identifications rather than upon the personality or demeanor of particular eyewitnesses.

Another vital evidential issue illuminated by behavioral science research concerns the probative value of admissions made by suspects under criminal investigation. Admissions of guilt are regarded as key items of evidence for the prosecution, but have come under critical scrutiny from researchers. The result is increasing recognition of the extent to which the readiness to confess to a crime may be influenced not only by improper pressure from police officers, but by personality traits peculiar to the individual which may cause him or her to make false admissions. This may occur without any impropriety on the part of investigators. The vulnerability of some suspects, such as those with low or borderline IQ, may be clear to courts and can be taken into account when considering the reliability of their admissions. In some cases, however, factors indicating that a confession should be viewed with caution are less obvious. This does not necessarily mean that courts will routinely accept expert evidence on the reliability of a confession. They tend to be most receptive to such evidence where the defendant has a personality disorder or learning difficulties, that is, at the more overtly scientific end of behavioral science typically involving clinical diagnosis. Yet even in a nonclinical case, there may be powerful personality factors indicating that the suspect’s confession should be treated with skepticism.

The psychological characteristics which need to be addressed are interrogative suggestibility and compliance, which are traits that may cause false admissions to be made once in police custody, even during perfectly proper and legitimate questioning by police officers. Suggestibility is a tendency to accept uncritically information communicated during questions. It is most pronounced in people of low intelligence. Gudjonsson (1992) has devised what he considers to be a reliable scale to assess suggestibility as a continuing condition, while allowing suggestibility may be aggravated by circumstances. Gudjonsson defines compliance as a tendency to go along with requests made by a person perceived to be in authority, even though the subject does not necessarily agree with or wholeheartedly endorse them. Building on these foundational concepts, Gudjonsson (1992) advanced a useful threefold classification of false confessions.

First, “voluntary” confessions are not induced by the police in any way; often there is no interview. The confession may constitute a response to publicity for a serious offense. Certain individuals are well known to their local police station for attempting to take responsibility for a whole series of crimes reported in the media. This kind of behavior may be motivated by a desire for notoriety, or to relieve a general feeling of guilt, or reflect an inability to distinguish fact and fantasy. A second kind of unreliable confession is the “coerced-compliant,” a false confession motivated by the desire to escape from a highly stressful situation, such as police custody The immediate gain, frequently nothing more than the need for short-term resolution and predictability of future events, becomes a more powerful influence on the subject’s behavior than the more uncertain long-term effects of the confession, even if the allegation concerns a serious offense. The majority of false confessions encountered in practice are coerced-compliant. Wagenaar concurs that common occasions for false confessions include the suspect taking an apparently easy way out, not anticipating the long-term consequences, perhaps thinking it will be possible to retract later, or choosing the only conceivable way out because the suspect is unable to cope with immediate pressures, for example, of confinement and interrogation, or a situation where the suspect is simply outwitted by the questioner – a not inconceivable event in the inevitably oppressive atmosphere of police custody (Wagenaar et al. 1993). A third category of false confession is the “coerced-internalized.” People who do not trust their own memory may begin to accept the suggestions of apparently authoritative and knowledgeable individuals, like police investigators. Such suspects may become temporarily persuaded that they might have, or did indeed, commit the crime. Such a confession is more likely to be elicited by gentle, rather than aggressive, interviewing. It may be retracted later on, although the subject is more likely to stick to internalized admissions than is the coercedcompliant confessor who never truly accepted responsibility in the first place. Even if a confession is later withdrawn, the subject’s memory may be permanently distorted (Wagenaar et al. 1993) and the confession itself might still be admissible in court.

Some legal jurisdictions recognize the risks involved in attributing significant evidential weight to confession evidence even in the absence of illegitimate pressure from the investigating authorities. Elsewhere, the psychology of false confessions is simply not recognized (see, e.g., Hodgson 2000’s depictions of French criminal process). In Scotland and the Netherlands, no one can be convicted on the strength of a confession alone. In some US jurisdictions, a police station confession by the defendant, without corroboration, is not considered sufficient to sustain a conviction. In jurisdictions without a general corroboration requirement, there may be particular protections for vulnerable suspects, as in England and Wales, but they tend to allow weak corroboration, such as the suspect’s “special knowledge” of circumstantial details that only the perpetrator of the crime would know, to support the admissibility of the confession. However, the notion that the suspect’s guilt is reliably confirmed by his awareness of facts not communicated to the public is a dubious method of corroborating confessions. There are documented instances of suspects who confess in apparent knowledge of such information, only later to be proved innocent in the light of further revelations. They must have become aware of the relevant facts at some point during the period of detention, possibly through careless “confabulation” whereby police interviewers unwittingly feed information to the suspect (Kassin and Wrightsman 1988).

In prosecutions of domestic violence, theories of learned helplessness in consequence of domestic abuse have been influential in developing defenses or partial defenses, for example, in murder cases where prolonged exposure to domestic abuse has apparently caused the victim to respond by killing the abuser. Colloquially known as “battered woman syndrome,” this psychological disorder is said to establish a causal relationship between the pattern of abuse suffered by the defendant, her psychological reactions to it, and her perception of her subsequent conduct. There is some evidence that lay persons, and therefore potential jurors, tend to consider that victims of domestic violence should leave home to escape it. This rationalist interpretation of behavior appears to be a powerful influence on jury reasoning, relatively impervious to expert evidence explaining why the obvious escape route is not employed in many such cases (Dodge and Green 1991). It is difficult to communicate to nonspecialists that prolonged experience of a highly controlled situation and exposure to violent sanctions for disobedience can reduce to vanishing point a person’s subjective free choice. A battered partner might have genuinely (and sometimes even reasonably) believed that deadly force was the only way to escape from a perilous situation in which his or her own life was in mortal danger (Ewing 1987).

Future Directions

Behavioral science research and expertise have influenced many aspects of criminal investigation and the way evidence is presented to the court. Psychological autopsies and offender profiling have assisted the police in some cases. Sociological and psychological research has established that the emphasis on orality of testimony has had a markedly detrimental effect on a whole range of witnesses who have in the past struggled with the performance elements of the adversarial trial. In many jurisdictions, the evidence of vulnerable witnesses is now facilitated by technological innovations such as “live link” videoconferencing or video recording (see, e.g., Roberts and Zuckerman 2010, Chap. 10). Criminal courts owe much to researchers in these fields. In addition, some aspects of behavioral science research are gaining ground in terms of providing evidence that may assist in reaching a verdict. Greater use of expert evidence in rape cases, in particular to dispel commonly held assumptions about the likely effect of having been raped upon a person’s demeanor and likely response, could be very useful.

However, behavioral science is not yet ready to assist the court with the most problematic and the most crucial of the judgments that the jury has to make, namely, whether someone is speaking the truth or telling lies. Experts are not allowed to testify as to the credibility of a particular witness, although they may be able to explain the effect of a mental disorder on sufferers in general. At the same time, the literature on what, if any, exhibited behaviors constitute evidence of lying is at best inconclusive (Vrij 2000). Some years ago na¨ıve faith in technological development encouraged flirtations with truth drugs and lie detector machines, but experience has since shown that they are not reliable indicators of dishonesty. Simple devices measuring levels of moisture on the palms of the hands may indicate nervousness, and nothing more (Saxe 1991). Polygraphs are used in criminal investigations in Canada, Israel, and Japan, but nowhere more than in the United States; albeit that courts in some US states will still not accept polygraph evidence (Patrick and Iacono 1991). In the United Kingdom, a working group produced such a devastating report on polygraph machines that the Government of the day abandoned any attempt to introduce them as a source of evidence in criminal trials (Working Group of the British Psychological Society on the Use of Polygraphs 1986).

The only conclusions to be drawn from the voluminous psychological literature on lying, credibility, and demeanor is that, first, neither laymen nor machines are accurate in recognizing liars or lies. Secondly, there is no valid scientific reason to believe that there is any observable indicator of lying behavior that an expert could use to identify it on behalf of fact finders in criminal adjudication. If the consequence of successful cross-examination in court is to produce behaviors commonly associated with lying but equally consistent with nervousness or confusion, the only inferential conclusions are negative. Behavioral science research certainly casts doubt on various familiar categories of evidence and challenges many commonly held lay assumptions capable of frustrating the courts’ truth-seeking function. Unfortunately, however, it cannot provide much in the way of positive information as to where the truth of the case lies. The credibility of a witness, or the weight to attach to their evidence, lies in the two issues of reliability, depending on memory, and truthfulness. Behavioral science can tell us only of generalities, not specifics. Were it otherwise, jury dominance over the ultimate issue could be challenged. Unless and until our understanding of human conduct and thinking develops into a demonstrably convincing and coherent scientific discipline affording positive, case-specific guidance to fact finders, jurors (and victims and defendants) will be left at the mercy of their “common-sense” perceptions of behavior – prejudices, stereotypes, myths, and all.


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