Open-source implementation of the Congruent Matching Cells method for cartridge case identification

Firearm evidence identification is the process of analyzing bullets or cartridge cases left at a crime scene to determine if they originated from a particular firearm. Statistical methods have long been developed and used to aid in such analyses. The Congruent Matching Cells (CMC) method is one such method developed at the National Institute of Standards and Technology (NIST) to quantify the similarity between two spent cartridge cases based on the markings left by the firearm barrel during the firing process. We introduce the first open-source implementation of the CMC method in the R package cmcR. The package will bolster forensic researchers\u27 abilities to investigate, validate, and improve upon current statistical methodology in the field of forensic science

Doctor of Philosophy

dissertationThis project is an activity-based study of American teens (13-17 years of age) and their material engagement with new media. This study documents the participants' engagement with new media in networked spaces and the everyday practices that surround their participation. Study participants were asked to orally report what they are experiencing as they experience it. Reports and on-screen activities are recorded by a laptop computer. Theoretical findings emerged from the axial coding across four code categories and suggested a leitmotiv pattern of a complex but stable relationship between interpersonal communication channels, the relative immediacy and intimacy of the channel, and the social relationship between participants. This pattern appeared to have a structuring influence on communication practices of youth in networked publics, and led to some tensions, concerns, and strategies relating to controlling the flow of information in those spaces. Overall, 10 code patterns and themes emerged to provide insight into the everyday practices of young people as they negotiate and construct meaning and identity in networked publics. The implications of the findings are discussed in the context; of the research questions. To my wife, Esther, for her love and unwavering support. To my children, who have never known a father who was not in working on a PhD. To my mother and father, who never lost confidence. My family was and is my inspiration

Open-source implementation of the Congruent Matching Cells method for cartridge case identification

Firearm evidence identification is the process of analyzing bullets or cartridge cases left at a crime scene to determine if they originated from a particular firearm. Statistical methods have long been developed and used to aid in such analyses. The Congruent Matching Cells (CMC) method is one such method developed at the National Institute of Standards and Technology (NIST) to quantify the similarity between two spent cartridge cases based on the markings left by the firearm barrel during the firing process. We introduce the first open-source implementation of the CMC method in the R package cmcR. The package will bolster forensic researchers' abilities to investigate, validate, and improve upon current statistical methodology in the field of forensic science.</p

A cartridge case comparison pipeline

Forensic examinations attempt to solve the binary classification problem of whether two pieces of evidence originated from the same source. Algorithms to compare evidence are increasingly proposed for use in forensic examinations to supplement an examiner's opinion with an objective measure of similarity. Given the gravity of the application, such algorithms must first be thoroughly tested under various conditions to identify strengths and weaknesses, which requires a good deal of experimentation. This experimentation is expedited when algorithms are intentionally developed to be accessible to the wider scientific community, including fellow researchers and practitioners. In this work, we discuss an algorithm to objectively measure the similarity between impressions left on cartridge cases during the firing process. We have designed this algorithm to be approachable for researchers and practitioners alike. Chapter 1 reviews current literature related to the next three chapters. Chapter 2 discusses a modularization of the algorithm into a pipeline that enables reproducibility, experimentation, and comprehension. Our goal in this modularization is to lay a foundation adherent to the "tidy" design principles upon which improvements can be easily developed. Chapter 3 details a suite of diagnostic tools that illuminate the inner workings of the algorithm and aid in identifying when and why the algorithm "works" correctly. These diagnostics will be useful for researchers interested in correcting the algorithm's behavior and practitioners concerned with interpreting the algorithm in casework. Chapter 4 introduces novel pipeline elements that we demonstrate are improvements to predominant methods. We introduce the Automatic Cartridge Evidence Scoring (ACES) algorithm that measures the similarity between two cartridge cases using a novel set of numeric features and a statistical classification model. We implement the various components of ACES in three R packages: cmcR, impressions, and scored, and provide a user-friendly interface for the algorithm in an interactive web application called cartridgeInvestigatR

A Pipeline for Cartridge Case Comparisons

We introduce novel sub-procedures in the pre-processing, comparison and similarity feature steps. The sub-procedures result in an improved error rate compared to our implementation of the CMC method while also requiring fewer parameters. The fitted Decision tree model is easily interpretable.The following poster was presented at the 106th International Association for Identification (IAI) Annual Educational Conference, Omaha, Nebraska, July 31-August 6, 2022. Posted with permission of CSAFE

A Study in Reproducibility: The Congruent Matching Cells Algorithm and cmcR Package

Scientific research is driven by our ability to use methods, procedures, and materials from previous studies and further research by adding to it. As the need for computationally-intensive methods to analyze large amounts of data grows, the criteria needed to achieve reproducibility, specifically computational reproducibility, have become more sophisticated. In general, prosaic descriptions of algorithms are not detailed or precise enough to ensure complete reproducibility of a method. Results may be sensitive to conditions not commonly specified in written-word descriptions such as implicit parameter settings or the programming language used. To achieve true computational reproducibility, it is necessary to provide all intermediate data and code used to produce published results. In this paper, we consider a class of algorithms developed to perform firearm evidence identification on cartridge case evidence known as the Congruent Matching Cells (CMC) methods. To date, these algorithms have been published as textual descriptions only. We introduce the first open-source implementation of the Congruent Matching Cells methods in the R package cmcR. We have structured the cmcR package as a set of sequential, modularized functions intended to ease the process of parameter experimentation. We use cmcR and a novel variance ratio statistic to explore the CMC methodology and demonstrate how to fill in the gaps when provided with computationally ambiguous descriptions of algorithms.This article is published as Zemmels, et al., "The R Journal: A Study in Reproducibility: The Congruent Matching Cells Algorithm and cmcR Package", The R Journal 14 (2023): 79-102. doi:10.32614/RJ-2023-014. Posted with permission of CSAFE.This article is licensed under the Creative Commons Attribution 4.0 International license (CC BY 4.0, http://creativecommons.org/licenses/by/4.0/)

Diagnostic Tools for Automatic Cartridge Case Comparisons

The following was presented at the Association of Firearm and Tool Mark Examiners (AFTE) 2023, Austin, Texas, May 21-26, 2023. Copyright 2023, The Authors. Posted with permission of CSAFE. Presentation is also available at this link

Annotated record of the detailed examination of Mn deposits from ARA Islas Orcadas Cruise 7 core stations

The purpose of this volume, the seventh in a series of similar publications (Goodell, 1964, 1965, 1968; Frakes 1971, 1973 ; Cassidy et al., 1977), is to continue a presentation to the research community of sediment core descriptions and attendant data of cored and otherwise obtained sediments retrieved in waters of the Southern Ocean aboard the research vessel, ARA Islas Orcadas (formerly, USNS Eltanin), as a part of the circumpolar survey begun by Eltanin in 1962 (see issue of Antarctic Journal of the United States, Vol. 8, No. 3, 1973). The data presented herein are concerned with the results of coring activities aboard cruise 0775 of Islas Orcadas, the second marine geology coring cruise of this vessel under the terms of the present United States-Argentine agreement. The core descriptions are organised as follows: 1) a brief summary of the coring objectives of the cruise, together with a discussion of core recovery; 2) a table and map of station location data for materials retrieved; 3) a table of tentative age-dates for each piston core; 4) an explanation of the laboratory procedures and descriptive criteria used in the description of the sediments, and 5) lithologic descriptions of the piston and trigger cores, and the piston and trigger core bag samples

Topographic Scans of Breech Face Impressions on Cartridge Case Primers

This repository contains topographic scans of breech face impressions on the surface of 2,625 fired cartridge case primers. We obtained these cartridge cases from the Defense Forensic Science Center (DFSC) Ames Lab I study. We provide this data set as a benchmark to develop and validate cartridge case processing and comparison algorithms.Topographic images of the cartridge case surfaces were taken using the Cadre Forensic (TM) TopMatch-3D High Capacity scanner at a resolution of approximately 1.8 micrometers ("microns") per pixel. Each image is digitally represented as a 2D array called a "surface matrix" containing the relative depth values of the cartridge case surface. Each surface matrix is saved along with metadata concerning the parameters under which the image was taken (including size, resolution, author, and others) to the x3p (XML 3D Surface Profile) file format. Additionally, each image is accompanied with a second 2D array of the same size called a "mask" representing manual annotations on the image. These manual annotations are intended to identify a region of the cartridge case surface containing "breech face impressions," which, analogous to a fingerprint, can be used to identify the firearm from which the cartridge case was fired.Apart from the original, full resolution topographic images, versions of each image undergoing various pre-processing steps are also included in the "sample_400_balanced," "sample_400"balanced_afterAutoPreproc_masks," and "sample_400_balanced_preprocessed" folders. These pre-processing steps are intended to isolate and emphasize the breech face impressions in the image. For example, manual annotations saved in the x3p mask are used to extract the breech face impression region away from the rest of the image. The "code/" folder contains an executable script written in the R programming language called "preProcess-scans.R" that fully reproduces the pre-processed scans. The "validation" folder contains results and reproducible code from applying a cartridge case comparison algorithm called the Congruent Matching Cells method. Additionally, the folder contains results from comparing NIST Standard Reference Material #2461 cartridge cases. These validations were performed to ensure that the scanning and processing procedures resulted in scans that accurately represent the original cartridge case surfaces.</p

Use of Online Media for Professional Development Amongst Medical Radiation Practitioners in Australia and Canada

Online media allows access to professional development (PD) regardless of geographical location and has the potential to provide equitable, immediate and quality PD. Online media includes online information and social media. The purpose of this mixed methods research study was to investigate the perceptions and use of online media for PD amongst medical radiation practitioners within Australia and Canada. An online survey was circulated to members of the Canadian Association of Medical Radiation Technologists (CAMRT) and the Australian Society of Medical Imaging and Radiation Therapy (ASMIRT). The survey collected data within three domains: current use, satisfaction of use, and future use. A four point Likert scale was used for both satisfaction with the online platform and frequency of use. Two hundred and thirty-nine responses were collected. Results indicated that the online mechanisms most frequently used by respondents for PD were Google, self-directed learning, and intranet. A correlating degree of satisfaction was indicated with the use of these platforms. The least used online media for PD were social media platforms including health related blogs, LinkedIn, Twitter, health related and professional applications, Facebook, and online journal clubs. Online media is well suited to PD for medical radiation practitioners. The platforms that are preferred offer speed and ease of access regardless of geographical location or occupation. Whilst inherent risks and instances of unprofessional online behaviour are acknowledged, Australian and Canadian practitioners are keen to learn what social media PD opportunities exist. Findings indicate that radiation therapists are more receptive to explore new social media platforms and tools than are radiographers. There is an opportunity to incorporate formal PD for medical radiation practitioners within recognised social media platforms