Do inconclusive forensic decisions disadvantage the innocent?

OBJECTIVE: Two experiments examined the potential for inconclusive forensic decisions to disadvantage the innocent. HYPOTHESES: Both experiments tested the hypothesis that inconclusive decisions produce more incriminating legal judgments than do clearly exculpatory forensic decisions. Experiment 2 also examined whether this hypothesized effect conformed to a confirmation bias, a communication error, or perceptual accuracy. METHOD: In Experiment 1 (N = 492), a forensic expert testified that physical evidence recovered from a crime scene either matched or did not match a suspect's evidence or produced an inconclusive result. In Experiment 2 (N = 1,002), a forensic expert testified that physical evidence recovered from a crime scene either matched or did not match a suspect's evidence, produced an inconclusive result, or was unsuitable for analysis. A fifth condition omitted the forensic evidence and expert testimony. RESULTS: The inconclusive decision produced less incriminating legal judgments than did the match forensic decision (|d|average = 0.96), more incriminating legal judgments than did the no-match forensic decision (|d|average = 0.62), and equivalent legal judgments to the unsuitable decision (|d|average = 0.12) and to legal judgments made in the absence of forensic evidence (|d|average = 0.07). These results suggest that participants interpreted the inconclusive decision to be forensically neutral, which is consistent with a communication error. CONCLUSION: The findings provide preliminary support for the idea that inconclusive decisions can put the innocent at risk of wrongful conviction by depriving them of a clearly exculpatory forensic decision. (PsycInfo Database Record (c) 2024 APA, all rights reserved).

Validity of forensic cartridge-case comparisons.

This article presents key findings from a research project that evaluated the validity and probative value of cartridge-case comparisons under field-based conditions. Decisions provided by 228 trained firearm examiners across the US showed that forensic cartridge-case comparison is characterized by low error rates. However, inconclusive decisions constituted over one-fifth of all decisions rendered, complicating evaluation of the technique's ability to yield unambiguously correct decisions. Specifically, restricting evaluation to only the conclusive decisions of identification and elimination yielded true-positive and true-negative rates exceeding 99%, but incorporating inconclusives caused these values to drop to 93.4% and 63.5%, respectively. The asymmetric effect on the two rates occurred because inconclusive decisions were rendered six times more frequently for different-source than same-source comparisons. Considering probative value, which is a decision's usefulness for determining a comparison's ground-truth state, conclusive decisions predicted their corresponding ground-truth states with near perfection. Likelihood ratios (LRs) further showed that conclusive decisions greatly increase the odds of a comparison's ground-truth state matching the ground-truth state asserted by the decision. Inconclusive decisions also possessed probative value, predicting different-source status and having a LR indicating that they increase the odds of different-source status. The study also manipulated comparison difficulty by using two firearm models that produce dissimilar cartridge-case markings. The model chosen for being more difficult received more inconclusive decisions for same-source comparisons, resulting in a lower true-positive rate compared to the less difficult model. Relatedly, inconclusive decisions for the less difficult model exhibited more probative value, being more strongly predictive of different-source status.

Unpacking insanity defence standards: an experimental study of rationality and control tests in criminal law / Descifrar los criterios de defensa de la vesania: estudio experimental de las pruebas de racionalidad y control en derecho penal

The present study investigated the impact of different legal standards on mock juror decisions concerning whether a defendant was guilty or not guilty by reason of insanity. Undergraduate students (N=477) read a simulated case summary involving a murder case and were asked to make an insanity determination. The cases differed in terms of the condition of the defendant (rationality deficit or control deficit) and the legal standard given to the jurors to make the determination (Model Penal Code, McNaughten or McNaughten plus a separate control determination). The effects of these variables on the insanity determination were investigated. Jurors also completed questionnaires measuring individualism and hierarchy attitudes and perceptions of facts in the case. Results indicate that under current insanity standards jurors do not distinguish between defendants with rationality deficits and defendants with control deficits regardless of whether the legal standard requires them to do so. Even defendants who lacked control were found guilty at equal rates under a legal standard excusing rationality deficits only and a legal standard excluding control and rationality deficits. This was improved by adding a control test as a partial defence, to be determined after a rationality determination. Implications for the insanity defence in the Criminal Justice System are discussed (AU)

Este estudio ha investigado la repercusión de los diversos cánones legales en las decisiones simuladas acerca de si un acusado es culpable o no por motivos de vesania. Una muestra de 477 estudiantes universitarios leyeron el resumen de caso relativo a un asesinato, pidiéndoseles luego que determinasen si había enajenación mental. Los casos diferían en cuanto a la condición del acusado (déficit de racionalidad o de control) y el criterio legal proporcionado a los jurados para que tomaran la determinación (Código penal modelo, McNaughten o McNaughten mas una determinación sobre el control). Se investigó el efecto de estas variables en la determinación de vesania. Los jurados rellenaron también cuestionarios que medían actitudes de individualismo y jerarquía y la percepción de los hechos del caso. Los resultados indican que con los criterios de demencia actuales los jurados no distinguen entre acusados con déficit de racionalidad y aquellos con déficit de control, aunque los criterios legales se lo exijan. Incluso los acusados que carecían de control fueron hallados culpables en la misma proporción con un criterio legal que disculpaba el déficit de racionalidad y con otro que excluía los déficit de control y racionalidad. Consiguió mejorarse añadiendo una prueba de control como defensa parcial a determinar tras la decisión sobre la racionalidad. Se comentan las implicaciones para la defensa de la enajenación mental en el sistema de justicia penal (AU)

Can Implicit Associations Distinguish True and False Eyewitness Memory? Development and Preliminary Testing of the IATe.

Eyewitness identification has been shown to be fallible and prone to false memory. In this study we develop and test a new method to probe the mechanisms involved in the formation of false memories in this area, and determine whether a particular memory is likely to be true or false. We created a seven-step procedure based on the Implicit Association Test to gauge implicit biases in eyewitness identification (the IATe). We show that identification errors may result from unconscious bias caused by implicit associations evoked by a given face. We also show that implicit associations between negative attributions such as guilt and eyewitnesses' final pick from a line-up can help to distinguish between true and false memory (especially where the witness has been subject to the suggestive nature of a prior blank line-up). Specifically, the more a witness implicitly associates an individual face with a particular crime, the more likely it is that a memory they have for that person committing the crime is false. These findings are consistent with existing findings in the memory and neuroscience literature showing that false memories can be caused by implicit associations that are outside conscious awareness. Copyright © 2017 John Wiley & Sons, Ltd.

Insight into children's prosocial lies: Comment on Warneken and Orlins.

In their article, Warneken and Orlins () provide insight into children's prosocial lie-telling. Their work adds to a growing body of literature regarding the development of prosocial behaviour and indicates that young children will tell 'white lies' in order to improve the mood of others. This work has important implications for forensic contexts that we note.