Jury Certainty about Firearms Evidence: Examination Effects

Firearms examiners routinely compare tool-marks on suspect ammunition with those on ammunition test-fired by a suspect weapon to evaluate if they can be associated. The discipline has been subject to criticism, including by the National Academy for Sciences, but the testimony of firearms examiners is routinely admitted as expert evidence in the United States (US). Jurors must determine the weight of expert evidence, which opposing and proffering lawyers can, respectively, discredit on cross-examination and rehabilitate on redirect-examination. The authors investigated the effect of both cross and redirect-examination on potential US jurors’ certainty about expert firearms evidence using a series of online vignettes. Participants (n=114) were asked to rate their certainty (on a scale of 0-100) about three expert statements – Very Certain (an exact match), Certain (a match to a reasonable degree of certainty), and Uncertain (evidence is unsuitable for comparison) – when assigned to one of three conditions. These conditions were a judicial instruction about weighing the evidence (control condition); a cross-examination referencing criticism of firearms evidence; and a redirect-examination referencing the routine admission of firearms evidence. Analysis was undertaken both between groups and between the statements given to each group. Results suggest that experts conveying high certainty create higher certainty in jurors, cross-examination has a detrimental effect on this certainty, but redirect-examination does not reduce this detrimental effect

Juror Certainty about Firearms Evidence: Examination Effects

Firearms examiners routinely compare tool-marks on suspect ammunition with those on ammunition test-fired by a suspect weapon to evaluate if they can be associated. The discipline has been subject to criticism, including by the National Academy of Sciences, but the testimony of firearms examiners is routinely admitted as expert evidence in the United States (US). Jurors must determine the weight of expert evidence, which opposing and proffering lawyers can aim to, respectively, discredit on cross-examination and rehabilitate on redirect-examination. The authors investigated the effect of both cross and redirect- examination on potential US jurors’ certainty about expert firearms evidence using a series of online vignettes. Participants (n=114) were asked to rate their certainty (on a scale of 0-100) about three expert statements – Very Certain (an exact match), Certain (a match to a reasonable degree of certainty), and Uncertain (evidence is unsuitable for comparison) – when assigned to one of three conditions. These conditions were a judicial instruction about weighing the evidence (control condition); a cross-examination referencing criticism of firearms evidence; and a redirect-examination (following the cross-examination) referencing the routine admission of firearms evidence. Analysis was undertaken both between groups and between the statements given to each group. Results suggest that experts conveying high certainty create higher certainty in jurors, cross-examination has a detrimental effect on this certainty, but redirect-examination does not reduce this detrimental effect

Juror Certainty about Firearms Evidence: Examination Effects

Firearms examiners routinely compare tool-marks on suspect ammunition with those on ammunition test-fired by a suspect weapon to evaluate if they can be associated. The discipline has been subject to criticism, including by the National Academy of Sciences, but the testimony of firearms examiners is routinely admitted as expert evidence in the United States (US). Jurors must determine the weight of expert evidence, which opposing and proffering lawyers can aim to, respectively, discredit on cross-examination and rehabilitate on redirect-examination. The authors investigated the effect of both cross and redirect- examination on potential US jurors’ certainty about expert firearms evidence using a series of online vignettes. Participants (n=114) were asked to rate their certainty (on a scale of 0-100) about three expert statements – Very Certain (an exact match), Certain (a match to a reasonable degree of certainty), and Uncertain (evidence is unsuitable for comparison) – when assigned to one of three conditions. These conditions were a judicial instruction about weighing the evidence (control condition); a cross-examination referencing criticism of firearms evidence; and a redirect-examination (following the cross-examination) referencing the routine admission of firearms evidence. Analysis was undertaken both between groups and between the statements given to each group. Results suggest that experts conveying high certainty create higher certainty in jurors, cross-examination has a detrimental effect on this certainty, but redirect-examination does not reduce this detrimental effect

Forensic Expert Evidence: Research Approaches to Judicial, Juror and Lawyer Decision-Making

In the United States, forensic science is vital for solving crimes, with forensic experts routinely testifying in legal proceedings. In doing so, forensic experts interact with key legal actors. Judges will determine the admissibility of the expert’s evidence, deliver jury instructions, and decide appeals. Lawyers will present and challenge the expert evidence, and jurors will weigh the evidence as part of determining a verdict. In this space, advances in DNA testing have led to concerns about the reliability of expert opinions concerning forensic comparison techniques like fingerprint and firearm analysis, which have served the criminal justice system for decades. The National Academy of Sciences has reported on these concerns, including the limitations of judges, lawyers, and jurors when it comes to understanding forensic science evidence. Against this backdrop, this chapter shares three research approaches developed by the authors to deepen understanding of judicial, juror, and lawyer decision-making about forensic science in context. It concludes with ideas for future research, including the relevance of these approaches to legal debates in England and Wales, Canada, and Australia

Juror Certainty about Expert Firearms Identification Evidence and the Impact of Cross-examination

To evaluate association, firearms examiners compare tool-marks present on suspect ammunition to those present on ammunition test-fired by a suspect weapon. Examiners’ conclusions are generally admissible in US courts, yet the scientific underpinnings of the discipline have been subject to considerable criticism. Cross-examination can be used to bring such criticism to the attention of jurors, who determine the weight of expert evidence. The authors investigated the effect of such cross-examination on juror certainty about expert firearms evidence using online vignettes. A community sample of US participants (n=437) were asked to rate their certainty (0-100) of a forensic match for each of 4 expert statements of certainty, in 2 groups; either with or without a cross-examination highlighting limitations of the tool-mark discipline’s scientific underpinnings. Analysis was undertaken both between groups and between the statements given to each group. Results suggest that cross-examination can have a strong influence on juror decision-making, particularly when experts express their conclusions in certain terms