Skip to content

Statistical modeling and analysis of trace element concentrations in forensic glass evidence

Journal: The Annals of Applied Statistics
Published: 2018
Primary Author: Karen D.H. Pan
Secondary Authors: Karen Kafadar
Research Area: Latent Print

The question of the validity of procedures used to analyze forensic evidence was raised many years ago by Stephen Fienberg, most notably when he chaired the National Academy of Sciences’ Committee that issued the report The Polygraph and Lie Detection [National Research Council (2003) The National Academies Press]; his role in championing this cause and drawing other statisticians to these issues continued throughout his life. We investigate the validity of three standards related to different test methods for forensic comparison of glass (micro X” role=”presentation” style=”margin: 0px; padding: 0px; border: 0px; font-variant-numeric: inherit; font-variant-east-asian: inherit; font-stretch: inherit; font-size: 14px; line-height: normal; font-family: “Helvetica Neue”, Helvetica, Arial, sans-serif; vertical-align: baseline; display: inline; overflow-wrap: normal; white-space: nowrap; float: none; direction: ltr; max-width: none; max-height: none; min-width: 0px; min-height: 0px; color: rgb(34, 34, 34); position: relative;”>XX-ray fluorescence (μ” role=”presentation” style=”margin: 0px; padding: 0px; border: 0px; font-variant-numeric: inherit; font-variant-east-asian: inherit; font-stretch: inherit; font-size: 14px; line-height: normal; font-family: “Helvetica Neue”, Helvetica, Arial, sans-serif; vertical-align: baseline; display: inline; overflow-wrap: normal; white-space: nowrap; float: none; direction: ltr; max-width: none; max-height: none; min-width: 0px; min-height: 0px; color: rgb(34, 34, 34); position: relative;”>μμ-XRF) spectrometry, ICP-MS, LA-ICP-MS], all of which include a series of recommended calculations from which “it may be concluded that [the samples] did not originate from the same source.” Using publicly available data and data from other sources, we develop statistical models based on estimates of means and covariance matrices of the measured trace element concentrations recommended in these standards, leading to population-based estimates of error rates for the comparison procedures stated in the standards. Our results therefore do not depend on internal comparisons between pairs of glass samples, the representativeness of which cannot be guaranteed: our results apply to any collection of glass samples that have been or can be measured via these technologies. They suggest potentially higher false positive rates than have been reported, and we propose alternative methods that will ensure lower error rates.

Related Resources

Does image editing improve the quality of latent prints? An analysis of image-editing techniques in one crime laboratory

Does image editing improve the quality of latent prints? An analysis of image-editing techniques in one crime laboratory

Field research within latent print comparison has remained sparse in the context of an otherwise growing body of literature examining the discipline. Studies examining how ACE-V procedures are implemented within…
Modeling Covarying Responses in Complex Tasks

Modeling Covarying Responses in Complex Tasks

In testing situations, participants are often asked for supplementary re- sponses in addition to the primary response of interest, which may in- clude quantities like confidence or reported difficulty. These…
Analyzing spatial responses: A comparison of IRT- based approaches, Conference Presentation

Analyzing spatial responses: A comparison of IRT- based approaches, Conference Presentation

We investigate two approaches for analyzing spatial coordinate responses using models inspired by Item Response Theory (IRT). In the first, we use a two-stage approach to first construct a pseudoresponse…