Forensic applications present unique challenges for statisticians. Until recently, it was difficult to find any relevant data that were non-proprietary and that were useful for research. Further, much of the data that arise in forensic problems are non-standard, and include low quality images, voice recordings, and stain patterns, to name a few. In those cases, even defining analytical variables may require out-of-the-box thinking. In criminal cases, the question of interest is often one of source. Some evidence is recovered from a crime scene; was the defendant the source of that evidence? For example, did the defendant’s gun fire the bullets embedded in a wall? Other forensic questions refer to the cause of an effect. Here, the difficulty arises because the standard causal framework is not appropriate to answer individual causation questions: we know that smoking causes cancer, but did it cause the cancer of the specific person who is suing a tobacco company? In consequence, it is often the case that traditional statistical approaches are not well suited to address the questions of interest to jurors, legal professionals and forensic practitioners.

The presentation introduces some of the statistical and algorithmic methods proposed recently that have the potential to impact forensic practice in the US. Some of this research is mature enough to be already undergoing pilot testing at actual crime labs, although no new technology has yet been implemented in real case work. Two examples are used for illustration: the analysis of questioned handwritten documents and of marks imparted by firearms on bullets or cartridge cases. In both examples, the question we address is the question of source: do two or more items have the same source? In the first case, we apply “traditional” statistical modeling methods, while in the second case, we resort to algorithmic approaches to quantify similarity between two items, followed by a statistical test for the hypothesis of same source.

About the Speaker:
Alicia Carriquiry is a Distinguished Professor of Liberal Arts and Sciences and a Professor of Statistics at Iowa State University. She researches applications of statistics in human nutrition, bioinformatics, forensic sciences and traffic safety, and has published over 100 peer-reviewed articles in corresponding academic journals. She received an MSc in animal sci­ence from the University of Illinois, and an MSc and a PhD in statistics and animal genetics from Iowa State University.

Dr. Carriquiry is the lead investigator for the CSAFE program, providing scientific oversight and research expertise. Along with Dr. Stern and Dr. Daniels, she was among the first to question the probative value of bullet lead analysis. A 2000 report to the FBI that suggested the probability of a coincidental match might not be negligible led to the establishment of a NAS committee to explore the issue. Carriquiry also served as a member of the NAS committee on ballistic imaging.

Professor Carriquiry has spoken at the International Conference on Forensic Inference and Statistics (ICFIS) and participates in the Forensic Sciences certificate program at Iowa State University. She also serves on the OSAC subcommittee on Materials and Trace Evidence, and was recently named to the National Academy of Medicine and elected as a fellow to AAAS.