Statistics in Court
In court, logic and reasoning prevails. Or does it?
Rules, reasoning, principles, logic -both the court of law and statistics base their foundation upon these. However, there are striking cases of egregious misuse of statistics in the court, especially when it comes to the evaluation of evidence and the probabilistic thinking required for it.
Today, while quality and availibility of forensic evidence is rising, the understanding of the evidence and the statistical methodology behind it drags behind. This necessitates the need for further research for statistics used in both the court and forensic science. Following links are samples of work that discusses how forensic evidence is received by the jury, the process in which the forensic evidence can have better quality assurance, and how to better evaluate evidence that was once thought to be unreliable.
Perceived Reliability of Eyewitness Statements
In contrast to the eyewitness testimonies at the time of trial, recent empirical works suggest that eyewitnesses' confidence statements at the time of initial identification may be a highly reliable indicator of accuracy. During the lineup, eyewitnesses are told to state in words how confident they are about the identification. For this study, a convenient sample of individuals online was asked to interpret how confident eyewitnesses are to observe the impacts of varying factors on the perception of eyewitness confidence.
The study shows that the frequency and severity, as expected, holds a significant impact on the perception of how confident the eyewitness was in the lineup. Somewhat interestingly, the race of lineup did not play a statistically significant role according to the dataset. The race, age, and state/region of the evaluator remain to be explored as a part of future analysis.
Perceived Reliability of Fingerprint Evidence
During many criminal cases, forensic evidence gathered by crime scene investigators and evaluated by a proficient examiner plays a critical role. Fingerprint impressions, among numerous types of forensic evidence, are the most common type used to link individuals to specific crimes. A proper understanding of how a juror may interpret a presentation of given evidence is critical in the strengthening of the current judicial system.
Analysis of the client (Prof. Brandon Garrett) dataset uncovered interesting results. Statistical modeling and tests support that, when presented with examiner evaluations, jurors' responses vary significantly. That is, the perceived reliability of evidence examined by examiners with a low error rate is statistically significantly higher than those from examiners with a high error rate. However, interestingly, the type of error that the examiner has made [false positive, false negative, or mixed] did not have a significant effect on the perceived reliability.
Analysis, Comparison, Evaluation, and Verification - a Methodology
The objective of this analysis was to determine any pattern or irregularities outside of normal assumptions in the dataset regarding the evaluation of latent prints by experts. The dataset contained more than 2,500 individual cases with 76 variables that, while not completely independent, is isolated. Latent prints and professional analysis of prints hold high value in courts, and no error should be permitted. Type I errors regarding innocence as null should be as low as possible, and this suggests that any minor improvements on the methodology of latent print analysis are critical. Simple descriptive statistical measures were used, and it was found that there is a statistically significant advantage to the ACE-V system having a verifying examiner.