How Jurors Evaluate Fingerprint Evidence: The Relative Importance of Match Language, Method Information, and Error Acknowledgment

Fingerprint examiners use a variety of terms and phrases to describe a finding of a match between a defendant\u27s fingerprints and fingerprint impressions collected from a crime scene. Despite the importance and ubiquity of fingerprint evidence in criminal cases, no prior studies examine how jurors evaluate such evidence. We present two studies examining the impact of different match phrases, method descriptions, and statements about possible examiner error on the weight given to fingerprint identification evidence by laypersons. In both studies, the particular phrase chosen to describe the finding of a match-whether simple and imprecise or detailed and claiming near certainty-had little effect on participants\u27 judgments about the guilt of a suspect. In contrast, the examiner admitting the possibility of error reduced the weight given to the fingerprint evidence-regardless of whether the admission was made during direct or cross-examination. In addition, the examiner providing information about the method used to make fingerprint comparisons reduced the impact of admitting the possibility of error. We found few individual differences in reactions to the fingerprint evidence across a wide range of participant variables, and we found widespread agreement regarding the uniqueness of fingerprints and the reliability of fingerprint identifications. Our results suggest that information about the reliability of fingerprint identifications will have a greater impact on lay interpretations of fingerprint evidence than the specific qualitative or quantitative terms chosen to describe a fingerprint match

How Jurors Evaluate Fingerprint Evidence: The Relative Importance of Match Language, Method Information, and Error Acknowledgment

Fingerprint examiners use a variety of terms and phrases to describe a finding of a match between a defendant\u27s fingerprints and fingerprint impressions collected from a crime scene. Despite the importance and ubiquity of fingerprint evidence in criminal cases, no prior studies examine how jurors evaluate such evidence. We present two studies examining the impact of different match phrases, method descriptions, and statements about possible examiner error on the weight given to fingerprint identification evidence by laypersons. In both studies, the particular phrase chosen to describe the finding of a match-whether simple and imprecise or detailed and claiming near certainty-had little effect on participants\u27 judgments about the guilt of a suspect. In contrast, the examiner admitting the possibility of error reduced the weight given to the fingerprint evidence-regardless of whether the admission was made during direct or cross-examination. In addition, the examiner providing information about the method used to make fingerprint comparisons reduced the impact of admitting the possibility of error. We found few individual differences in reactions to the fingerprint evidence across a wide range of participant variables, and we found widespread agreement regarding the uniqueness of fingerprints and the reliability of fingerprint identifications. Our results suggest that information about the reliability of fingerprint identifications will have a greater impact on lay interpretations of fingerprint evidence than the specific qualitative or quantitative terms chosen to describe a fingerprint match

The Proficiency of Experts

Expert evidence plays a crucial role in civil and criminal litigation. Changes in the rules concerning expert admissibility, following the Supreme Court\u27s Daubert ruling, strengthened judicial review of the reliability and the validity of an expert\u27s methods. Judges and scholars, however, have neglected the threshold question for expert evidence: whether a person should be qualified as an expert in the first place. Judges traditionally focus on credentials or experience when qualifying experts without regard to whether those criteria are good proxies for true expertise. We argue that credentials and experience are often poor proxies for proficiency. Qualification of an expert presumes that the witness can perform in a particular domain with a proficiency that non-experts cannot achieve, yet many experts cannot provide empirical evidence that they do in fact perform at high levels of proficiency. To demonstrate the importance ofproficiency data, we collect and analyze two decades of proficiency testing of latent fingerprint examiners. In this important domain, we found surprisingly high rates of false positive identifications for the period 1995 to 2016. These data would qualify the claims of many fingerprint examiners regarding their near infallibility, but unfortunately, judges do not seek out such information. We survey the federal and state case law and show how judges typically accept expert credentials as a proxy for proficiency in lieu of direct proof of proficiency. Indeed, judges often reject parties\u27 attempts to obtain and introduce at trial empirical data on an expert\u27s actual proficiency. We argue that any expert who purports to give falsifiable opinions can be subjected to proficiency testing and that proficiency testing is the only objective means of assessing the accuracy and reliability ofexperts who rely on subjective judgments to formulate their opinions (so-called black-box experts ). Judges should use proficiency data to make expert qualification decisions when the data is available, should demand proof of proficiency before qualifying black-box experts, and should admit at trial proficiency data for any qualified expert. We seek to revitalize the standard for qualifying experts: expertise should equal proficiency

Forensics and Fallibility: Comparing the Views of Lawyers and Jurors

Forensic evidence plays an increasingly prominent role in criminal practice, leading some to worry that depictions in popular media might make jurors over-reliant on forensics — a so-called CSI effect. There is little empirical evidence of such a CSI effect among jury-eligible laypersons; any such influence also depends upon a case proceeding to a trial. As the Supreme Court has put it: “criminal justice today is for the most part a system of pleas, not a system of trials.” However, a CSI effect could be more consequential if it affects how criminal lawyers assess forensic evidence when they negotiate pleas or decide what evidence to present at trial. In this Essay, we begin to examine how criminal defense lawyers and prosecutors assess forensics, and we compare their views to those expressed by lay jurors. Part I of this Essay surveys the literature on the role that evidence plays in the plea bargaining process. In Part II, we present the results of two surveys that examine views on fingerprint and DNA evidence. Our focus was on two types of forensics: DNA evidence and fingerprint evidence. The evidence we gathered suggests misperceptions of both the evidence and how jurors will view the evidence. We found defense lawyers, in particular, may be far more skeptical of forensic evidence than jurors; indeed, defense lawyers may be overly skeptical of even DNA evidence. Most remarkable, however, was the great weight that jury-eligible adults placed on fingerprint evidence, just as many of the lawyers surveyed would have predicted, and even when compared to the weight they placed on DNA evidence. These results suggest far more must be done to study what information and influences shape the weight both lawyers and jurors place on forensics. We conclude in Part III by outlining how these surveys can provide a useful starting place for further research and policy

Error Aversions and Due Process

William Blackstone famously expressed the view that convicting the innocent constitutes a much more serious error than acquitting the guilty. This view is the cornerstone of due process protections for those accused of crimes, giving rise to the presumption of innocence and the high burden of proof required for criminal convictions. While most legal elites share Blackstone’s view, the citizen-jurors tasked with making due process protections a reality do not share the law’s preference for false acquittals over false convictions. Across multiple national surveys, sampling more than 10,000 people, we find that a majority of Americans views false acquittals and false convictions to be errors of equal magnitude. Contrary to Blackstone, most people are unwilling to err on the side of letting the guilty go free to avoid convicting the innocent. Indeed, a sizeable minority views false acquittals as worse than false convictions; this group is willing to convict multiple innocent persons to avoid letting one guilty person go free. These value differences translate into behavioral differences: we show in multiple studies that jury-eligible adults who reject Blackstone’s view are more accepting of prosecution evidence and more conviction prone than the minority of potential jurors who agrees with Blackstone. These findings have important implications for our understanding of due process and criminal justice policy. Due process currently depends on jurors faithfully following instructions on the burden of proof, but many jurors are not disposed to hold the state to its high burden. Courts should do away with the fiction that the reasonable doubt standard guarantees due process and consider protections that do not depend on jurors honoring the law’s preference for false acquittals, such as more stringent pre-trial screening of criminal cases and stricter limits on prosecution evidence. Furthermore, the fact that many people place crime control on par with, or above, the need to avoid wrongful convictions helps explain divisions in public opinion on important policy questions such as bail and sentencing reform. Criminal justice proposals that emphasize deontic concerns without addressing consequentialist concerns are unlikely to garner widespread support

Error Aversions and Due Process

William Blackstone famously expressed the view that convicting the innocent constitutes a much more serious error than acquitting the guilty. This view is the cornerstone of due process protections for those accused of crimes, giving rise to the presumption of innocence and the high burden of proof required for criminal convictions. While most legal elites share Blackstone’s view, the citizen jurors tasked with making due process protections a reality do not share the law’s preference for false acquittals over false convictions. Across multiple national surveys sampling more than 12,000 people, we find that a majority of Americans consider false acquittals and false convictions to be errors of equal magnitude. Contrary to Blackstone, most people are unwilling to err on the side of letting the guilty go free to avoid convicting the innocent. Indeed, a sizeable minority view false acquittals as worse than false convictions; this group is willing to convict multiple innocent persons to avoid letting one guilty person go free. These value differences translate into behavioral differences: we show in multiple studies that jury-eligible adults who reject Blackstone’s view are more accepting of prosecution evidence and are more conviction-prone than the minority of potential jurors who agree with Blackstone. These findings have important implications for our understanding of due process and criminal justice policy. Due process currently depends on jurors faithfully following instructions on the burden of proof, but many jurors are not inclined to hold the state to its high burden. Courts should do away with the fiction that the reasonable doubt standard guarantees due process and consider protections that do not depend on jurors honoring the law’s preference for false acquittals, such as more stringent pretrial screening of criminal cases and stricter limits on prosecution evidence. Further, the fact that many people place crime control on par with, or above, the need to avoid wrongful convictions helps explain divisions in public opinion on important policy questions like bail and sentencing reform. Criminal justice proposals that emphasize deontic concerns without addressing consequentialist concerns are unlikely to garner widespread support

The impact of proficiency testing information and error aversions on the weight given to fingerprint evidence

Fingerprint examiners regularly participate in tests designed to assess their proficiency. These tests provide information relevant to the weight of fingerprint evidence, but no prior research has directly examined how jurors react to proficiency testing information. Using a nationally representative sample of American adults, we examined the impact of proficiency testing information on the weight given to the opinions of fingerprint examiners by mock jurors considering a hypothetical criminal case. The fingerprint examiner\u27s level of performance on a proficiency test (high, medium, low, or very low), but not the type of error committed on the test (false positive identifications, false negative identifications, or a mix of both types of error), affected the weight that jury‐eligible adults gave to an examiner\u27s opinion that latent fingerprints recovered from a crime scene matched the defendant\u27s fingerprints, which in turn affected judgments about the defendant\u27s guilt. Jurors who had no information about proficiency gave similar weight to the testimony as jurors exposed to highly proficient examiners, suggesting that jurors assume fingerprint examiners perform at high levels of proficiency unless informed otherwise. We also found that a plurality of Americans deems false acquittals just as aversive as false convictions and a significant minority deems false acquittals more serious. These differences in error aversions predicted differences in evidentiary assessments, suggesting that error aversions of jurors may play an important role in criminal trials