Psychology in the Courtroom: The Expert Witness Study Guide

Definition and Admissibility of the Expert Witness

  • Definition by the CPS (2014): An expert witness is defined as "a witness who provides to the court a statement of opinion on any admissible matter calling for expertise by the witness and is qualified to give such an opinion."

  • Purpose of Expert Evidence: According to the Criminal Practice Direction V Evidence 19A Expert Evidence, this testimony is admissible to furnish the court with information likely to be outside the experience and knowledge of a judge or jury.

  • Role and Duties of an Expert Witness:     * To assist the court by providing objective, unbiased opinion evidence restricted to the limits of their expertise.     * To identify the boundaries of their expertise and alert the court if a question falls outside their specific competence.     * To inform all parties and the court if their opinion changes from a previously submitted report or statement, including an explanation for that change.

  • Types of Expert Witnesses: The court utilizes experts in various fields, including DNA, Ear prints, Fingerprints, Footwear Impressions, Forensic Pathology, Hypnosis, Medical, Psychological Autopsies, Voice Recognition, and Handwriting.

  • Admissibility Standards:     * The judge determines if expert evidence is admissible.     * The Law Commission Report (2011) suggested that expert evidence was previously too readily accepted with little scrutiny.     * Recommended Statutory Admissibility/Reliability Test:         1. It will be of assistance to the court.         2. The expert possesses relevant expertise.         3. The expert is impartial.         4. The expert's evidence is reliable.

Historical Context of Psychologist Experts

  • First Recorded Case (1896): German Psychologist Albert von Schrenck-Notzing testified in the case of a Munich man accused of murdering three women. He noted the confusion among witnesses between what they actually saw and what they subsequently learned about the event.

  • Early US Context: Around the same time, Hugo Munsterberg acted as a psychological consultant on two murder trials in the United States.

Juror Processing and the Helpfulness of Experts

  • Processing Routes:     * Central Route: Systematic and effortful processing of information.     * Peripheral Route: Reliance on mental short-cuts and heuristics.

  • Effectiveness Concerns: There are ongoing concerns that jurors and judges may not fully comprehend trial evidence. However, Bornstein & Greene (2011) indicate that jurors generally consider evidence carefully.

  • The Problem in Eyewitness Testimony: Jurors often overestimate the reliability of eyewitnesses.

  • McCloskey & Egeth (1983) - Goals of Expert Testimony:     * To correct juror misunderstandings and assist in distinguishing reliable from unreliable testimony.     * Findings: Neither goal was achieved. Jurors were no better at distinguishing accuracy, and the evidence made them more skeptical without improving verdict accuracy.

Professional Impact on Juror Perceptions

  • Increased Scepticism: Research by Hosch et al. (1980), Loftus (1980), and Wells et al. (1980) suggests expert evidence increases juror skepticism.

  • Wells et al. (1980) Mock Juror Study:     * Involved a staged crime where mock jurors either received expert testimony or no expert evidence.     * Result: Expert testimony reduced the believed accuracy of the witness identification but did not necessarily improve discrimination accuracy.

  • Sensitization and Scrutiny:     * Hosch, Beck, & McIntyre (1980): Expert testimony increases mock jurors' scrutiny of evidence.     * Cutler, Dexter & Penrod (1989) / Geiselman et al. (2002): Testimony sensitized jurors to the limitations of eyewitness accounts.     * Cutler, Dexter, & Penrod (1990): Confirmed the trend of increased juror skepticism.

Expert Witnesses and Myth-Debunking

  • Impact of Rape Myths (Lonsway and Fitzgerald, 1994): If a judge or jury believes such myths, it can lead to erroneous case dismissal, not guilty verdicts, or reduced sentences.

  • Definition of Myths (Burt, 1980): "Prejudicial, stereotyped, or false beliefs."

  • Backfire Effects in Debunking:     * Familiarity Backfire Effect (Skurnik et al., 2005): Attempting to undermine myths by emphasizing they are false can sometimes reinforce the myth in memory.     * Overkill Backfire Effect (Sanna et al., 2002): Refuting myths with too many facts can be counterproductive.

  • Strategies for Experts: Avoid discussing myths directly; focus on facts. If a myth must be mentioned, state it is incorrect, provide the reason why the myth exists, and use diagrams or illustrations to improve comprehension.

  • Counteracting Myths and Influencing Outcomes:     * Brekke & Borgida (1988): Testimony reduced belief in rape myths in simulated trials.     * Goodman-Delahunty et al. (2011): Corrected misconceptions regarding children’s memory in CSA cases.     * Conviction Rates: Prosecution expert testimony increases conviction rates (Kovera et al., 1994), while defense expert testimony reduces them (Schuller & Hastings, 1996).

Expert Testimony as a Safeguard and Mitigator

  • Opposing Expert Testimony (Levett and Kovera, 2008):     * Study on whether opposing experts educate jurors about unreliable testimony.     * Findings: Presence of an opposing expert increased skepticism of expert evidence and the likelihood of a guilty verdict while decreasing the credibility/trustworthiness ratings of the defense expert.

  • Mitigating Invalid Forensic Evidence (Eastwood & Caldwell, 2015):     * Participants evaluated a sexual assault case involving invalid hair comparison evidence.     * Findings: The presence of an expert witness reduced guilty verdicts and the perceived credibility of the victim while strengthening the defense's case. Judicial instructions had absolutely no effect on juror perception.

Extra-Legal Factors and Expert Influence

  • Neuroscientific Evidence (e.g., fMRI):     * Saks et al. (2014): Neuroimages bolstered arguments compared to neuroscientific evidence without images (small effect varying by mental illness diagnosis).     * Schweitzer et al. (2011): Neuroimages had no effect on verdicts or sentence recommendations.

  • The Likeability Factor (Brodsky et al., 2009):     * Involves verbal and nonverbal components: pleasantry, smiling, attractiveness, language, tone, and eye contact.     * Findings: High likeability increases perceived credibility and trustworthiness but has no significant effect on final juror decision-making.

  • Complexity and Credentials (Cooper, Bennett, and Sukel, 1996):     * When testimony is complex, participants are more persuaded by strong credentials (credential-based shortcut).     * When testimony is simple, jurors are influenced more by what is said than by credentials.

  • Training and Experience (Ferreira & Wingrove, 2023):     * PhD vs. Masters: PhD experts were rated as more credible only when the evidence had high validity (included a control group). If validity was low, qualifications had no effect on credibility.

Gender, Presentation, and Non-Verbal Cues

  • Gender Congruence (McKimmie et al., 2004): Damage awards were greater when the gender of the expert and the case domain (e.g., cosmetic sales vs. automobile services) were congruent.

  • Language and Gender (McKimmie et al., 2013):     * Stereotypes: Complex language is associated with males; simple language with females.     * Findings: Female experts using complex language were perceived as less persuasive.

  • Appearance and Posture (Jones et al., 2023):     * Female experts were perceived as more credible when presented in a gender-typical way.     * A skirt suit was perceived as more credible than a trouser suit, but specifically when the expert maintained a closed posture (clenched hands, crossed arms, body leaned away).

  • Confidence (Cramer et al., 2011): Expert confidence is positively correlated with death sentence decisions and higher credibility.

  • Eye Contact (Neal and Brodsky, 2011):     * Credibility ratings increase as eye contact increases.     * Female experts were rated more credible than males at each level of contact.     * For male experts, high and medium eye contact resulted in significantly higher credibility than low contact.

Summary of Findings

  • Criminal trials increasingly rely on expert witnesses to shape juror understanding of complex evidence.

  • Juror outcomes are determined by a mix of Content factors (strength, clarity), Delivery factors (eye contact, communication style), and Expert characteristics (gender, credentials).

  • Decisions are not only influenced by the content of the expert's words but also by how they are presented.