implementing 3d virtual comparison comparison · virtual microscopy results •3445 total virtual...
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Implementing 3D Virtual Comparison Microscopy into Forensic Firearm/Toolmark
Comparison Heather Seubert– Unit Chief/Firearms Examiner
FBI Laboratory
2501 Investigation Parkway
Quantico, VA 22135
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FBI Laboratory, Firearms/Toolmarks Unit, Quantico, VA
• 19 - Technical Personnel • (Examiners/Technicians/Evidence Support)
• 3 - Administrative Support
• Forensic Examinations • Firearms, Toolmarks, Distance Determination, Ammunition
Components, Serial Number Restoration
• Crime Scene Response • Shooting Trajectory Analysis
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FBI Firearms/Toolmarks Unit (FTU) Research Group Virtual Topography Goal
Can technology be used to enhance the forensic pattern based discipline of firearms/toolmark identification by providing objective information to establish a statistical significance and the associated uncertainty with a
conclusion?
The Federal Bureau of Investigation does not support or endorse any of the products that will be discussed during the course of this presentation.
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Cartridge Case Firearm
Breechface
Firing Pin Impression
Aperture Firing Pin
Breechface
Aperture
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FBI/FTU Research Group Virtual Topography
• Sensofar®-Confocal, Interferometry, and Focus Variation 2013
• Alicona®- Infinite Focus- Focus Variation 2014
• EvoFinder® - 2015
• GIGAMacro® - 2016
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FBI/FTU Research Group Virtual Topography Comparison/Evaluation
• Cadre Forensics® – TopMatch GS 3D - 2012, Photometric Stereo
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FBI/FTU Research Group Virtual Topography Comparison/Evaluation Phase I • Phase 1 : Assessing recorded images with 3D detail to evaluate whether this
methodology is more specific than traditional comparison
• Proficiency Tests – Proficiency Tests from 2003-2015 • Virtual Comparison (VC) evaluation -Completed 2016 • 927 Virtual Comparisons - no False ID (FID)
• Consecutive Manufactured Barrels/Slides • VC evaluation -Completed 2016 • 1602 virtual comparisons – no False ID (FID)
• Validation of VC microscopy involving casework – Completed 2017
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Original Comparison 2016-01426-6
• Item 1: 9mm Luger (9x19) CZ Pistol, Model 75B
• Item 2: Cartridge Case
• The Item 2 cartridge case was identified as having been fired in the Item 1 pistol.
• Blind verification – second examiner
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Virtual comparison 2016-01426-6
VC Test Design: • Decision already rendered CM • Evidence relabeled •Ground truths added •Proctor •Algorithm blocked from examiner
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Ground Truth 2016-01426-6
5 Correct Eliminations Selected
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Ground Truth – Identification 2016-01426-6
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Virtual Comparison Result 2016-01426-6
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Comparison Image Virtual Image
Item A – Laboratory Number 2016-02830
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Virtual Microscopy Results 2016-01426-6 • Participants recorded 24 correct identifications with 1 inconclusive for
“true” identification results.
• Test Sensitivity1: the number of correct identifications divided by the
number of exam results for “true” identifications. [24/(25x5)]= 0.192,
[25/(25x5) ]= 0.2, 0.192/0.2= 96%.
• Test Specificity1: the number of correct exclusions divided by the number of exam results for “true” exclusions (20 true exclusions, 11 Exclusions, 9 Inconclusive) = 55%, similar class characteristics – FTU SOP2 “an elimination occurs when there is a discernible or measurable difference in class characteristics.”
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Virtual Microscopy Results • 3445 Total Virtual Comparisons with No False Positives, 916 VC evidence
from casework
• Inconclusive decision changed using VC
• Standard Operating Procedure
• Live May, 2017
• Phase II Collaboration with NIST (2014) to determine an objective degree of similarity between two toolmarks as well as attaching an error rate to the analysis.
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Coming Soon Decision Analysis Study for Firearms
• FBI Laboratory and Ames Laboratory
Decision Analysis Study (DAS) is designed to provide the
forensic community quantifiable metrics on accuracy, repeatability, and reproducibility.
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Firearms/Toolmarks Unit
Thank You to Erich Smith (FTU), Jennifer Stephenson (FTU), and our partners at NIST.