A call for open science in forensics.

The modern canon of open science consists of five "schools of thought" that justify unfettered access to the fruits of scientific research: i) public engagement, ii) democratic right of access, iii) efficiency of knowledge gain, iv) shared technology, and v) better assessment of impact. Here, we introduce a sixth school: due process. Due process under the law includes a right to "discovery" by a defendant of potentially exculpatory evidence held by the prosecution. When such evidence is scientific, due process becomes a Constitutional mandate for open science. To illustrate the significance of this new school, we present a case study from forensics, which centers on a federally funded investigation that reports summary statistics indicating that identification decisions made by forensic firearms examiners are highly accurate. Because of growing concern about validity of forensic methods, the larger scientific community called for public release of the complete analyzable dataset for independent audit and verification. Those in possession of the data opposed release for three years while summary statistics were used by prosecutors to gain admissibility of evidence in criminal trials. Those statistics paint an incomplete picture and hint at flaws in experimental design and analysis. Under the circumstances, withholding the underlying data in a criminal proceeding violates due process. Following the successful open-science model of drug validity testing through "clinical trials," which place strict requirements on experimental design and timing of data release, we argue for registered and open "forensic trials" to ensure transparency and accountability.

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.

Risk assessment of child-pornography-exclusive offenders.

OBJECTIVES: A sizeable percentage of federally sentenced child pornography offenders have no history of other criminal offenses (hereinafter "child-pornography-exclusive offenders"). There is a critical legal need to assess the recidivism risk of this population. The Child Pornography Offender Risk Tool (CPORT) is a commonly used actuarial instrument developed specifically to assess the risk of recidivism among child pornography offenders. HYPOTHESES: We hypothesized that there would be a sound scientific basis supporting the use of the CPORT in the United States as well as research demonstrating its applicability to child-pornography-exclusive offenders, given that the instrument is currently being used in forensic settings. METHOD: We critically examined all of the existing empirical studies that constitute the research base of the CPORT. RESULTS: The empirical studies of the CPORT suffer from at least three significant limitations: extremely small samples of recidivists, inordinate amounts of missing data, and potentially outdated samples. Further, none of the studies have tested the CPORT in a sample of offenders in the United States. An illustrative example of how the instrument has been misapplied in forensic settings and courtroom testimony is provided. CONCLUSIONS: These issues make it inappropriate to use the CPORT on child-pornography-exclusive offenders in the United States at this time. We conclude by describing avenues for future research that can advance our understanding of this distinct and growing population of offenders. (PsycInfo Database Record (c) 2023 APA, all rights reserved).

Surveying practicing firearm examiners.

A sample (n = 79) of practicing firearm and toolmark examiners was queried about casework as well as their views about the potential role that statistics might play in future firearm examinations and expert witness testimony. Principal findings include: The modal response for time spent conducting bullet examinations is 2-4 hours, and the modal response for cartridge casings is 1-2 hours. The average participant (median) makes an identification in 65% of casework, makes an elimination in 12% of casework, and reports that the examination was inconclusive in 20% of casework calls. The vast majority of examiners work at laboratories that permit eliminations when class characteristics agree. The reported industry-wide false positive error rate is 1%, though very few participants could name a study or give a citation for their reported estimate. Qualitative responses about the potential role of statistics were mixed.

State v. Yepez: Admissibility and Relevance of Behavioral Genetic Evidence in a Criminal Trial.

The New Mexico Supreme Court recently considered whether a trial court had erred in excluding behavioral genetic evidence of a murder defendant's low-activity monoamine oxidase A (MAOA) gene, which the defendant argued had predisposed him-along with his history of childhood maltreatment-to "maladaptive or violent behavior." After an extensive analysis of the underlying science and its relevance to the case, the supreme court held unanimously that the trial judge had the discretion to exclude the MAOA evidence. The court's analysis provides insights into how other courts are likely to rule on the relevance of behavioral genetic evidence.

Mock jurors' evaluation of firearm examiner testimony.

OBJECTIVES: Firearms experts traditionally have testified that a weapon leaves "unique" toolmarks, so bullets or cartridge casings can be visually examined and conclusively matched to a particular firearm. Recently, due to scientific critiques, Department of Justice policy, and judges' rulings, firearms experts have tempered their conclusions. In two experiments, we tested whether this ostensibly more cautious language has its intended effect on jurors (Experiment 1), and whether cross-examination impacts jurors' perception of firearm testimony (Experiment 2). HYPOTHESES: Four hypotheses were tested. First, jurors will accord significant weight to firearm testimony that declares a "match" compared to testimony that does not (Experiments 1 and 2). Second, variations to "match" language will not affect guilty verdicts (Experiment 1). Third, only the most cautious language ("cannot exclude the gun") would lower guilty verdicts (Experiment 1). Fourth, cross-examination will reduce guilty verdicts depending on specific language used (Experiment 2). METHOD: In two preregistered, high-powered experiments with 200 mock jurors per cell, participants recruited from Qualtrics Panels were presented with a criminal case containing firearms evidence, which varied the wording of the examiner's conclusion and whether cross-examination was present. These variations include conclusion language used by practitioners, language advised by government organizations, and language required by judges in several cases. Participants gave a verdict, rated the evidence and expert in all conditions. RESULTS: Guilty verdicts significantly increased when a match was declared compared to when a match was not declared. Variation in conclusion language did not affect guilty verdicts nor did it affect jurors' estimates of the likelihood the defendant's gun fired the bullet recovered at the crime scene. In contrast, however, a more cautious conclusion that an examiner "cannot exclude the defendant's gun" did significantly reduce guilty verdicts and likelihood estimates alike. The presence of cross-examination did not affect these findings. CONCLUSION: Apart from the most limited language ("cannot exclude the defendant's gun"), judicial intervention to limit firearms conclusion language is not likely to produce its intended effect. Moreover, cross-examination does not appear to affect perceptions or individual juror verdicts. (PsycInfo Database Record (c) 2020 APA, all rights reserved).

Impact of risk assessment on judges' fairness in sentencing relatively poor defendants.

OBJECTIVE: Use of risk assessment instruments in the criminal justice system is controversial. Advocates emphasize that risk assessments are more transparent, consistent, and accurate in predicting re-offending than judicial intuition. Skeptics worry that risk assessments will increase socioeconomic disparities in incarceration. Ultimately, judges make decisions-not risk assessments. This study tests whether providing risk assessment information interacts with a defendant's socioeconomic class to influence judges' sentencing decisions. HYPOTHESES: Tentatively, socioeconomic status was expected to have a main effect; without an interaction with risk assessment information. METHOD: Judges (N = 340) with sentencing experience were randomly assigned to review 1 of 4 case vignettes and sentence the defendant to probation, jail, or prison. Information in the vignettes was held constant, except the defendant's socioeconomic status and whether risk assessment information was provided. RESULTS: Risk assessment information reduced the likelihood of incarceration for relatively affluent defendants, but the same information increased the likelihood of incarceration for relatively poor defendants. This finding held after controlling for the sex, race, political orientation, and jurisdiction of the judge. CONCLUSIONS: Cuing judges to focus on risk may re-frame how they process socioeconomic status-a variable with opposite effects on perceptions of blameworthiness for past crime versus perceptions of risk for future crime. Providing risk assessment information may have transformed low socioeconomic status from a circumstance that reduced the likelihood of incarceration (by mitigating perceived blameworthiness) to a factor that increased the likelihood of incarceration (by increasing perceived risk). Under some circumstances, risk assessment information may increase sentencing disparities. (PsycINFO Database Record (c) 2020 APA, all rights reserved).

(Mis)use of scientific measurements in forensic science.

Forensic science error rate studies have not given sufficient attention or weight to inconclusive evidence and inconclusive decisions. Inconclusive decisions can be correct decisions, but they can also be incorrect decisions. Errors can occur when inconclusive evidence is determined as an identification or exclusion, or conversely, when same- or different-source evidence is incorrectly determined as inconclusive. We present four common flaws in error rate studies: 1. Not including test items which are more prone to error; 2. Excluding inconclusive decisions from error rate calculations; 3. Counting inconclusive decisions as correct in error rate calculations; and 4. Examiners resorting to more inconclusive decisions during error rate studies than they do in casework. These flaws seriously undermine the credibility and accuracy of error rates reported in studies. To remedy these shortcomings, we present the problems and show the way forward by providing a corrected experimental design that quantifies error rates more accurately.

The dark figure of sexual recidivism.

Empirical studies of sexual offender recidivism have proliferated in recent decades. Virtually all of the studies define recidivism as a new legal charge or conviction for a sexual crime, and these studies tend to find recidivism rates of the order of 5-15% after 5 years and 10-25% after 10+ years. It is uncontroversial that such a definition of recidivism underestimates the true rate of sexual recidivism because most sexual crime is not reported to legal authorities, a principle known as the "dark figure of crime." To estimate the magnitude of the dark figure of sexual recidivism, this paper uses a probabilistic simulation approach in conjunction with the following: (i) victim self-report survey data about the rate of reporting sexual crime to legal authorities; (ii) offender self-report data about the number of victims per offender; and (iii) different assumptions about the chances of being convicted of a new sexual offense given that it is reported. Under any configuration of assumptions, the dark figure is substantial, and as a consequence the disparity between recidivism defined as a new legal charge or conviction for a sex crime and recidivism defined as actually committing a new sexual crime is large. These findings call into question the utility of recidivism studies that rely exclusively on official crime statistics to define sexual recidivism, and highlight the need for additional, long-term studies that use a variety of different measures to assess whether or not sexual recidivism has occurred.

How Cross-Examination on Subjectivity and Bias Affects Jurors' Evaluations of Forensic Science Evidence.

Contextual bias has been widely discussed as a possible problem in forensic science. The trial simulation experiment reported here examined reactions of jurors at a county courthouse to cross-examination and arguments about contextual bias in a hypothetical case. We varied whether the key prosecution witness (a forensic odontologist) was cross-examined about the subjectivity of his interpretations and about his exposure to potentially biasing task-irrelevant information. Jurors found the expert less credible and were less likely to convict when the expert admitted that his interpretation rested on subjective judgment, and when he admitted having been exposed to potentially biasing task-irrelevant contextual information (relative to when these issues were not raised by the lawyers). The findings suggest, however, that forensic scientists can immunize themselves against such challenges and maximize the weight jurors give their evidence by adopting context management procedures that blind them to task-irrelevant information.

Effects of the putative confession instruction on perceptions of children's true and false statements.

The putative confession (PC) instruction (i.e., "[suspect] told me everything that happened and wants you to tell the truth") during forensic interviews with children has been shown to increase the accuracy of children's statements, but it is unclear whether adults' perceptions are sensitive to this salutary effect. The present study examined how adults perceive children's true and false responses to the PC instruction. Participants (n = 299) watched videotaped interviews of children and rated the child's credibility and the truthfulness of his/her statements. When viewing children's responses to the PC instruction, true and false statements were rated as equally credible, and there was a decrease in accuracy for identifying false denials as lies. These findings suggest that participants viewed the PC instruction as truth-inducing. Implications for the forensic use of the PC instruction are discussed.

The case against categorical risk estimates.

Risk estimates can be communicated in a variety of forms, including numeric and categorical formats. An example of the latter is "low/medium/high risk." The categorical format is preferred by judges and practitioners alike, and is mandated by the most commonly utilized forensic risk assessment instruments (the HCR-20 and the Static-99). This article argues against the practice of communicating risk in categorical terms on empirical and normative grounds. Empirically, there is no consensus about what level of risk corresponds to a particular category, such as "high risk." Moreover, recent studies indicate that categorizing an otherwise continuous risk estimate does not add incremental predictive validity to the risk estimate. Normatively, categorization obscures what is fundamentally a value judgment about the relative costs and benefits of correct (e.g., true positive) and incorrect (e.g., false positive) outcomes. Such a judgment is inherently non-scientific and invades the province of the jury. Indeed, categorical risk estimates are in principle no different than "dangerousness predictions," which are simply binary and which have been denounced by the field. The fact that alternative risk communication formats have limitations does not justify continuing the pervasive practice of communicating categorical risk estimates.

When does absence of evidence constitute evidence of absence?

Negative forensic evidence can be defined as the failure to find a trace after looking for it. Such evidence is often dismissed by referring to the aphorism "absence of evidence is not evidence of absence." However, this reasoning can be misleading in the context of forensic science. This commentary is designed to help forensic scientists understand the probative value of negative forensic evidence.

Comparing Categorical and Probabilistic Fingerprint Evidence.

Fingerprint examiners traditionally express conclusions in categorical terms, opining that impressions do or do not originate from the same source. Recently, probabilistic conclusions have been proposed, with examiners estimating the probability of a match between recovered and known prints. This study presented a nationally representative sample of jury-eligible adults with a hypothetical robbery case in which an examiner opined on the likelihood that a defendant's fingerprints matched latent fingerprints in categorical or probabilistic terms. We studied model language developed by the U.S. Defense Forensic Science Center to summarize results of statistical analysis of the similarity between prints. Participant ratings of the likelihood the defendant left prints at the crime scene and committed the crime were similar when exposed to categorical and strong probabilistic match evidence. Participants reduced these likelihoods when exposed to the weaker probabilistic evidence, but did not otherwise discriminate among the prints assigned different match probabilities.

Mental state at time of offense in the hot tub: An empirical examination of concurrent expert testimony in an insanity case.

The role of experts and their presentation of testimony in insanity cases remain controversial. In order to decrease possible expert bias associated with this testimony, a number of different alternatives to adversarial presentation have been suggested. Two such alternatives are the use of court-appointed experts and the use of concurrent testimony (or "hot-tubbing"), in which opposing experts provide testimony concurrently and converse with each other directly. An experiment using a sample of venire jurors (n = 150) tested the effect of these alternatives. Results indicate that participants' pre-existing attitudes towards the insanity defense had significant effects on their comprehension of expert testimony, their evaluations of the two opposing experts, and their eventual verdicts, over and above the presentation format (i.e., concurrent vs. traditional testimony) or the use of court-appointed experts (vs. traditional adversarial experts). When concurrent testimony was presented, defense-favoring experts were perceived by jurors as more credible than their traditional counterparts, though comprehension of the testimony did not increase; nor did the presentation format or the affiliation of the experts affect verdicts. The legal and policy implications of the incorporation of the hot-tubbing procedure to US courts are discussed.