The Role of the Expert Witness in Forensic Psychology

by

Camilla Beeley, Gabriele Trupp, Daniel Murrie

• LAST MODIFIED: 22 August 2023
• DOI: 10.1093/obo/9780199828340-0319

Introduction

The legal system routinely relies on experts to help shed light on scientific or technical matters that are usually beyond the knowledge of the judges and attorneys involved, or the layperson jurors who render verdicts in many cases. These experts can come from virtually any discipline, because virtually any subject matter can become a focus of litigation. Experts from any subfield of psychology (e.g., developmental, cognitive, social, or industrial-organizational psychology) may testify when their input is relevant. Of course, the broad discipline of forensic psychology—that is, psychology applied to legal matters—most often features experts providing input to the legal system. Furthermore, this field of forensic psychology has generated much of the research addressing expert testimony, and that research is potentially instructive to expert witnesses from any discipline. Expert witnesses can be retained by either side in adversarial proceedings, but judges—following legal rules of evidence—make the final decision as to whether the expert is admitted to testify. Judges may also independently appoint an expert, though this occurs far less often. Regardless of how the expert was retained or appointed, experts in psychology should testify in a manner consistent with the American Psychological Association’s Ethical Principles of Psychologists and Code of Conduct, as well as the Specialty Guidelines for Forensic Psychology. Though their testimony must be honest and objective, experts also strive to be effective, delivering testimony that is clear and compelling. In pursuing effective and compelling testimony, experts in forensic psychology may consult a rich body of literature—ranging from rigorous empirical studies to lists of practical tips—that guide the content and delivery of expert testimony.

Overviews of Expert Testimony

An early guide to a range of aspects of forensic mental health practice, particularly testimony, is available in Blau 1998. To present a comprehensive overview of expert testimony, Cutler and Kovera 2011 reviews research on various types of testimony and identifies suggestions for additional research. Banks and Packer 2007 discusses the history, strategies, and ethics of expert witness testimony. The classic and influential text Melton, et al. 2018 addresses elements central to expert testimony and how to deliver testimony in a variety of situations. Marion, et al. 2019 also reviews relevant research related to testimony content, process, and helpfulness. Heilbrun, et al. 2014 provides advice on delivering expert testimony, emphasizing clear and effective communication. Lastly, Erickson and Ewing 2013 offers a succinct chapter on the growth and regulation of expert testimony in relation to the legal system, with areas for the ethical expert to avoid in practice.

• Banks, S. C., and I. K. Packer. 2007. Expert witness testimony: Law, ethics, and practice. In Forensic psychology: Emerging topics and expanding roles. Edited by A. M. Goldstein, 421–445. Hoboken, NJ: John Wiley & Sons.

  This chapter addresses the historical evolution of expert testimony, different stages of testimony, and commentary on how experts can provide expert testimony using the Courtroom Communications Model. The authors also discuss ethical considerations in the expert’s role.

• Blau, T. H. 1998. The psychologist as expert witness. 2d ed. Hoboken, NJ: John Wiley & Sons.

  In his broad book, Blau provides an overview of the ways in which psychology intersects with the law, including expert witness testimony. In discussing expert testimony, he provides examples of more and less effective testimony, reviews guidelines for testimony addressing different types of forensic referral questions, and emphasizes general standards of practice for providing expert testimony.

• Cutler, B. L., and M. B. Kovera. 2011. Expert psychological testimony. Current Directions in Psychological Science 20.1: 53–57.

  DOI: 10.1177/0963721410388802

  This article provides an overview of many aspects of expert testimony, including topics of testimony, admissibility of testimony, and research related to testimony.

• Erickson, D. A., and C. P. Ewing. 2013. Legal contours of expert testimony. In Handbook of Psychology. Vol. 11, Forensic psychology. 2nd ed. Edited by R. K. Otto, 62–74. Hoboken, NJ: John Wiley & Sons.

  This chapter discusses the historical emergence of psychological experts, the legal system that dictates and regulates psychological expert testimony, and areas that experts should avoid when providing psychological testimony.

• Heilbrun, K., D. DeMatteo, S. B. Holliday, and C. LaDuke. 2014. Expert testimony. In Forensic mental health assessment: A casebook. 2d ed. Edited by K. Heilbrun, D. DeMatteo, S. B. Holliday, and C. LaDuke, 576–598. New York: Oxford Univ. Press.

  DOI: 10.1093/med:psych/9780199941551.003.0027

  In this chapter of a much broader casebook of forensic assessment, the authors discuss how experts providing testimony can communicate effectively, connect their testimony to their mental health assessment, and then control the meaning and impact of their testimony. Each of these principles is accompanied by a teaching point to assist with practical application, including the review of a forensic report and the content that may be subject to cross-examination.

• Marion, S., J. Kaplan, and B. Cutler. 2019. Expert testimony. In Psychological science and the law. Edited by N. Brewer and A. B. Douglass, 318–337. New York: Guilford Press.

  Within a book about the application of psychological science in the legal system, this chapter by Marion and colleagues reviews expert testimony, including research relevant to the process that occurs prior to testimony and the research relevant to testimony in the courtroom. The authors discuss many topics relevant to the empirical basis of psychological testimony, expert bias, the helpfulness of testimony, and the different aspects of the testimony process.

• Melton, G. B., J. Petrila, N. G. Poythress, et al. 2018. Consultation, report writing, and expert testimony. In Psychological evaluations for the courts: A handbook for mental health professionals and lawyers. 4th ed. By G. B. Melton, J. Petrila, N. G. Poythress, et al., 575–606. New York: Guilford Press.

  Within the most influential and long-standing text on forensic mental health evaluations is a chapter addressing consultation, report writing, and expert testimony. Melton and colleagues discuss different stages of testimony, and how to address different elements or questions that may arise during testimony. The authors also address important considerations for conveying testimony effectively and empirical findings about lay attitudes toward experts.