Scientific guidelines for evaluating the validity of forensic feature-comparison methods.

When it comes to questions of fact in a legal context-particularly questions about measurement, association, and causality-courts should employ ordinary standards of applied science. Applied sciences generally develop along a path that proceeds from a basic scientific discovery about some natural process to the formation of a theory of how the process works and what causes it to fail, to the development of an invention intended to assess, repair, or improve the process, to the specification of predictions of the instrument's actions and, finally, empirical validation to determine that the instrument achieves the intended effect. These elements are salient and deeply embedded in the cultures of the applied sciences of medicine and engineering, both of which primarily grew from basic sciences. However, the inventions that underlie most forensic science disciplines have few roots in basic science, and they do not have sound theories to justify their predicted actions or results of empirical tests to prove that they work as advertised. Inspired by the "Bradford Hill Guidelines"-the dominant framework for causal inference in epidemiology-we set forth four guidelines that can be used to establish the validity of forensic comparison methods generally. This framework is not intended as a checklist establishing a threshold of minimum validity, as no magic formula determines when particular disciplines or hypotheses have passed a necessary threshold. We illustrate how these guidelines can be applied by considering the discipline of firearm and tool mark examination.

The Use of Battered Woman Syndrome in U.S. Criminal Courts.

Although not recognized by any edition of the Diagnostic and Statistical Manual of Mental Disorders, battered woman syndrome (BWS) has been offered as a defense in U.S. criminal courts for several decades. This article reviews examples of criminal cases in which BWS has been used in the United States as well as the implications of BWS for the practice of forensic psychiatry. Historically raised in cases of self-defense, BWS has also been used in criminal defenses involving duress, as well as by prosecutors to explain witness recantations. Case law suggests that expert witness testimony on BWS is often admissible in jurisdictions across the United States, yet its use in criminal defenses has received mixed responses from various courts. We examine limitations on the use of BWS in criminal courts and the potential use of posttraumatic stress disorder as an alternative and more reliable diagnosis in similar legal contexts.

Psychological Assessments in Legal Contexts: Are Courts Keeping "Junk Science" Out of the Courtroom?

In this article, we report the results of a two-part investigation of psychological assessments by psychologists in legal contexts. The first part involves a systematic review of the 364 psychological assessment tools psychologists report having used in legal cases across 22 surveys of experienced forensic mental health practitioners, focusing on legal standards and scientific and psychometric theory. The second part is a legal analysis of admissibility challenges with regard to psychological assessments. Results from the first part reveal that, consistent with their roots in psychological science, nearly all of the assessment tools used by psychologists and offered as expert evidence in legal settings have been subjected to empirical testing (90%). However, we were able to clearly identify only about 67% as generally accepted in the field and only about 40% have generally favorable reviews of their psychometric and technical properties in authorities such as the Mental Measurements Yearbook. Furthermore, there is a weak relationship between general acceptance and favorability of tools' psychometric properties. Results from the second part show that legal challenges to the admission of this evidence are infrequent: Legal challenges to the assessment evidence for any reason occurred in only 5.1% of cases in the sample (a little more than half of these involved challenges to validity). When challenges were raised, they succeeded only about a third of the time. Challenges to the most scientifically suspect tools are almost nonexistent. Attorneys rarely challenge psychological expert assessment evidence, and when they do, judges often fail to exercise the scrutiny required by law.

Promises, promises for neuroscience and law.

Stunning technical advances in the ability to image the human brain have provoked excited speculation about the application of neuroscience to other fields. The 'promise' of neuroscience for law has been touted with particular enthusiasm. Here, we contend that this promise elides fundamental conceptual issues that limit the usefulness of neuroscience for law. Recommendations for overcoming these challenges are offered.

Neuroscientists in court.

Neuroscientific evidence is increasingly being offered in court cases. Consequently, the legal system needs neuroscientists to act as expert witnesses who can explain the limitations and interpretations of neuroscientific findings so that judges and jurors can make informed and appropriate inferences. The growing role of neuroscientists in court means that neuroscientists should be aware of important differences between the scientific and legal fields, and, especially, how scientific facts can be easily misunderstood by non-scientists, including judges and jurors.

Psychological evidence at the dawn of the law's scientific age.

The Supreme Court's 1993 decision in Daubert v. Merrell Dow Pharmaceuticals, Inc., holding that the admissibility of scientific evidence depends on its scientific merit, has made American law receptive to valid science to an unprecedented degree. We review the implications for psychology of the law's taking science seriously. We consider the law before Daubert, and the ways that Daubert as well as modifications to the Federal Rules of Evidence have affected the admissibility of expert testimony. We describe the ramifications of these changes for psychology used as authority to create a general legal rule, as evidence to determine a specific fact, and as framework to provide context. Finally, future prospects for improving psychological testimony are offered: Court-appointed experts will increase the psychological sophistication of judges and juries, and evidence-based practices on the part of psychologists will increase the sophistication of the expert testimony that they proffer in court.