Accuracy of comparison decisions by forensic firearms examiners

Journal of Forensic Sciences, Journal Year: 2022, Volume and Issue: 68(1), P. 86 - 100

Published: Oct. 1, 2022

Abstract This black box study assessed the performance of forensic firearms examiners in United States. It involved three different types and 173 volunteers who performed a total 8640 comparisons both bullets cartridge cases. The overall false‐positive error rate was estimated as 0.656% 0.933% for cases, respectively, while false negatives 2.87% 1.87% respectively. majority errors were made by limited number examiners. Because chi‐square tests independence strongly suggest that probabilities are not same each examiner, these maximum‐likelihood estimates based on beta‐binomial probability model do depend an assumption equal examiner‐specific rates. Corresponding 95% confidence intervals (0.305%, 1.42%) (0.548%, 1.57%) positives (1.89%, 4.26%) (1.16%, 2.99%) results this consistent with prior studies, despite its comprehensive design challenging specimens.

Language: Английский

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Development of a competency test model to evaluate forensic identification officers on crime scene processing

Canadian Society of Forensic Science Journal, Journal Year: 2025, Volume and Issue: unknown, P. 1 - 10

Published: Feb. 3, 2025

Proficiency testing is required to ensure quality, efficiency, and safety in many disciplines. Multiple proficiency tests exist for forensic disciplines such as fingerprint analysis toxicology, but minimal research has been conducted on the of crime scene experts. The foundation an effective test rests upon development competency tests. Here, a proof-of-concept was designed example how evaluate processing skills identification officers (FIOs) using mock scenario. three main components: i) approach test, ii) evidence iii) general knowledge with pre-test demographic questions. content process reviewed by two experts (manuscript co-authors) viability. Due its digital format, this widely accessible, user-friendly, can be template police service develop their own or internal specialized tasks comparison estimation area origin bloodstain pattern (BPA) help mitigate risks identify gaps.

Language: Английский

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Evaluating firearm examiner conclusion variability using cartridge case reproductions

Journal of Forensic Sciences, Journal Year: 2021, Volume and Issue: 66(5), P. 1704 - 1720

Published: May 31, 2021

Abstract The forensic science pattern comparison areas, including fingerprints, footwear, and firearms, have been criticized for their subjective nature. While much research has attempted to move these disciplines more objective methods, examiners are still coming conclusions based on own training experience. To complement this subjectivity, black box studies necessary establish the accuracy of feature‐comparison methods. However, when cartridges fired by a firearm create cartridge case test sets there may be significant variability within resulting impressions. This can result in different participants receiving with varying levels difficulty differences impression quality. Therefore, between is not straightforward. compare examiners, method called double‐casting was used plastic reproductions. Double‐casts twenty‐one master cases were created mailed examiners. double‐casts ensured that all comparing exhibits same level detail. tasked determining if unknown each set as three knowns. Automated comparisons also set. results from study showed examiner examining evidence. Furthermore, it shown automated metrics would benefit quality control measure correct any potential errors strengthen conclusions.

Language: Английский

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Firearm examination: Examiner judgments and computer‐based comparisons

Journal of Forensic Sciences, Journal Year: 2020, Volume and Issue: 66(1), P. 96 - 111

Published: Sept. 24, 2020

Abstract Forensic firearm examination provides the court of law with information about source fired cartridge cases. We assessed validity decisions a computer‐based method and 73 examiners who compared breechface firing pin impressions 48 comparison sets. also method's scores examiners' degree‐of‐support judgments latter. The true‐positive rate (sensitivity) true‐negative (specificity) (for both impressions) were 94.4% at least 91.7%, respectively. For examiners, was 95.3% 86.2%. improved when evaluations combined for perceived difficulty decreased. reluctant to provide "difficult" comparisons even though their mostly correct. correlation between low same‐source negligible different‐source comparisons. Combining outcomes methods could increase examinations. numerical not well‐calibrated showed clear signs overconfidence. suggest studying merits performance feedback calibrate these judgments.

Language: Английский

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Forensic comparison of fired cartridge cases: Feature-extraction methods for feature-based calculation of likelihood ratios

Forensic Science International Synergy, Journal Year: 2022, Volume and Issue: 5, P. 100272 - 100272

Published: Jan. 1, 2022

We describe and validate a feature-based system for calculation of likelihood ratios from 3D digital images fired cartridge cases. The includes database the bases 10 cartridges per firearm approximately 300 firearms same class (semi-automatic pistols that fire 9 mm diameter centre-fire Luger-type ammunition, have hemispherical firing pins parallel breech-face marks). were captured using Evofinder®, an imaging is commonly used by operational forensic laboratories. A key component research reported comparison different feature-extraction methods. Feature sets compared include those previously proposed in literature, plus Zernike-moment based features. Comparisons are also made feature extracted firing-pin impression, region, whole region interest (firing-pin impression + flowback if present). Likelihood calculated statistical modelling pipeline standard voice comparison. Validation conducted results assessed validation procedures metrics graphics

Language: Английский

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Objective Identification of Bullets Based on 3D Pattern Matching and Line Counting Scores

International Journal of Pattern Recognition and Artificial Intelligence, Journal Year: 2019, Volume and Issue: 33(11), P. 1940021 - 1940021

Published: Feb. 19, 2019

In firearm identification, a examiner looks at pair of fired bullets or cartridge cases using comparison microscope and determines from this visual analysis if they were both the same firearm. particular case bullets, individual signature takes form striated pattern. Over time, examiner’s community developed two distinct approaches for bullet identification: pattern matching line counting. More recently, emergence technology enabling capture surface topographies down to submicron depth resolution has been catalyst field computerized objective ballistic identification. Objectiveness is achieved through statistical various scores known matches nonmatches exhibit comparison, which in turn implies large quantities topographies. The main goal study was develop an identification method conventionally rifled barrels, test on public proprietary 3D image datasets captured different lateral resolutions. Two newly scores, Line Counting Score (LCS) Pattern Matching Score, computed yielded perfect match versus nonmatch separation three sets used standard Hamby–Brundage Test. A similar performed larger, more-realistic set, enabled us define discriminative false rate 1/10[Formula: see text]000 2D plot that shows nonmatches. LCS shown produce better sensitivity than consecutive striae criteria dataset. likelihood function also linear combination conservative approach based extreme value theory proposed extrapolate score domain where data are not available. This provides understanding limitations studies involve very few firearms.

Language: Английский

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Convergence‐improved congruent matching cells (CMC) method for firing pin impression comparison

Journal of Forensic Sciences, Journal Year: 2020, Volume and Issue: 66(2), P. 571 - 582

Published: Nov. 23, 2020

Abstract A firing pin impression is usually concave in shape with a small textured area, which makes it difficult to perform automated algorithm‐based comparison. The congruent matching cells (CMC) method was invented for accurate breech face comparison, reference divided into correlation cells. Each cell registered cell‐sized area of the comparison that has maximum similarity surface topography. Four parameters are used quantify pattern registration position and orientation. This paper aims further develop cell‐division‐matching based on convergence feature practical convergence‐improved algorithms refers tendency x ‐ y positions correlated pairs converge at correct angle when comparing same‐source samples different orientations. areal Gaussian filter employed extract high‐frequency micro‐features; least‐squares improve each cross‐correlation precision reach pairs; density‐based clustering algorithm introduced collect dense relative virtual common center remove outliers. Improvements achieved reliability accuracy number (CMCs) collected, represents quantification degree pairwise similarity. Experiments this report 40 cartridge cases fired from 10 pistols. results included no false identifications or exclusions.

Language: Английский

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Interpol review of forensic firearm examination 2016-2019

Forensic Science International Synergy, Journal Year: 2020, Volume and Issue: 2, P. 389 - 403

Published: Jan. 1, 2020

This review paper covers the relevant literature on forensic firearm examination from 2016 to 2019 as a part of 19th Interpol International Forensic Science Managers Symposium. The papers are also available at website at: https://www.interpol.int/content/download/14458/file/Interpol%20Review%20Papers%202019.pdf.

Language: Английский

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Fringe projection profilometry for recovering 2.5D shape of ancient coins

ACTA IMEKO, Journal Year: 2021, Volume and Issue: 10(1), P. 142 - 142

Published: March 31, 2021

<p class="Abstract">The relief of form is undoubtedly one the most topical topics in field cultural heritage. Physical access to historic and artistic manufactures can be limited by a lot factors. For example, collection ancient coins difficult, especially for students. Indeed, digital archive high-quality three-dimensional model remote fruition great interest. The use projected fringes measurement surface profile well-developed technique. In this paper, we present system small objects heritage where it important not only detect shape with good accuracy but also capture signs due ageing. illustrated equipment simple, reliable, cheap. Furthermore, some examples acquisitions are presented demonstrate potentiality proposed scheme recovering 2.5D objects.</p>

Language: Английский

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Evaluation of GLOCK 9 mm Firing Pin Aperture Shear Mark Individuality Based on 3,156 Different Pistols (Manufactured Over a 30 Year Period in Two Countries) Using Additional Pattern Matching and IBIS Pattern Recognition

Arab Journal of Forensic Sciences and Forensic Medicine, Journal Year: 2024, Volume and Issue: 6(Special Issue), P. 104 - 116

Published: July 22, 2024

Over a period of 30 years, number fired GLOCK cartridge cases have been evaluated. A total 3156 firearms were used to generate sample the same size. Our research hypothesis was that no from different 9 mm semiautomatic pistols would be mistaken as coming gun (a false match). Using optical comparison microscopy, two separate experiments carried out test this hypothesis. subsample 617 test-fired subjected algorithmic by Integrated Ballistics Identification System (IBIS). The second experiment full set 3,156 manual comparisons using traditional pattern matching. None “matched” either these experiments. empirical findings, an established conservative Bayesian probability model estimate chance case, GLOCK, could firearm when in fact it did not (i.e., match probability).

Language: Английский

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