Firearms & Ballistics Lecture Notes PDF

Firearms & Ballistics LEC08 – Friday October 4th FRSC2030H Foundations in Forensic Science  Online Test 1 LAB02 Ending Online Lab Assignment 1 Posted Course Update Watch Last Week Tonight Video Read PCAST Re...

Firearms & Ballistics LEC08 – Friday October 4th FRSC2030H Foundations in Forensic Science  Online Test 1 LAB02 Ending Online Lab Assignment 1 Posted Course Update Watch Last Week Tonight Video Read PCAST Report Answer questions LEC09 & LAB03 Forensic Anthropology Reading Week (21st – 25th) The Beltway Snipers Feb – Sept 2002 >7 shot dead, several injured Several robberies October 3rd 2002 2 hours 7 people shot dead Tip called in about Muhammed & Malvo Verified by traffic stop violations Liquor store robbery Fingerprint left behind Arrested and weapon seized Classification of Firearms Firearms Handguns (pistols) Single shot handguns, revolvers, and semiautomatics Long guns Rifles Lands & grooves Lever-action, pump (slide-action), bolt-action, semiautomatic, automatic Shotguns Smooth Shells Double and single barrel Anatomy of Ballistics Ballistics Study of projectiles Cartridge Projectile (bullet) Casing Powder Primer Stamp Rimfire vs centre fire Anatomy of Firearms Gun barrel Solid bar of steel which has been burrowed Unique bore for each Manufacturers create lands and grooves Known as rifling Promotes spin and consistency of weapon Steel hook cutters, broach cutters, button impression, mandrel-rifling Caliber – diameter of the bore (gauge for shotguns) Usually in hundredths of an inch or millimeters Class characteristics maintained.32-caliber Smith & Wesson à 5.32-caliber Colt à 6 Individualizing Firearms Firearm identification Discipline concerned with determining whether a bullet or cartridge was fired by a particular weapon Individual Characteristics Striations Impressed during rifling process Unique to each weapon Test firing weapons Comparison of resulting bullets Under a comparison microscope Class characteristics compared first Then individualization begins Firing pin impressions Existing Database Integrated Ballistics Identification System (IBIS) Run by ATF National Integrated Ballistics Information Network (NIBIN) Developed in 1999 Tracks over 100,000 guns used in Crimes Generates several potential matches 75%-95% chance of a successful match Current Topics Topics Firearm examination Technical examination Shooting incident reconstruction Wound ballistics “validity and reliability of firearm examiners’ source judgments and how these can be affected by bias” “several studies have been performed with the aim to strengthen both the foundational validity of firearm examination as well as to provide insight into the validity as applied” Validation Studies Consecutively Manufactured Firearms 10 different 9 mm Loger Ruger P-85 (0.053%) 20 years, 697 participants, 240 test sets 30 different Berretta 9 mm Luger (0.55%) 74 examiners Durability test 500 shots with Glock “showed a decrease in the observed degree of similarity, the authors could still assign the 500th bullet to the first” 3000 shots Chinese Norinco QSZ-92 9 mm Luger pistols “the results show that similarity decreases slightly over time, but not so much that bullets were not correctly ranked” Ejection port marks from Glocks “the marks do not seem to reproduce well, as variation in shape and location was observed” Parameters Affecting ID of Firearms Methanol-based dyes for latent prints “functioned properly with no obvious metal reaction” DNA “dunking” Severe effects observed Addinall et al. – Firing pin impression metallic composition “has an effect on the areal topography of the firing pin impression” Authors: “care should be taken when correlating areal impressions with a dissimilar substrate material” Triki et al. – Firing pin impressions and firing modes Stable in single shot mode “In burst mode the depth and diameter of the impressions increase after each shot” Unusual Markings Smith – Altered parts Soot examination & chamber examination Kohn & Hazon et al. – Homemade parts Typical marks identified Swanepoel – Magazine marks Class and individual characteristics found Scheuerman – Bolt-action cycling Result of firing not cycling Kokin – Execution of Russian Emperor Nicholas II Bullets found >70 years after still allowed examiners to make comparisons and identifications Examiner Proficiency Mattijssen et al. – Validity and reliability of examiners Asked to provide source judgment Different source: Examiner > Computer based Same source: Examiner < Computer based Mattijssen et al. – Examiner Judgments Breechface & firing pin impressions 95.3% for examiners & 94.4% for computer based methods Different source: 91.7% computer based & 86.2% for examiners Chapnick et al. – Visual Comparison Microscopy (VCP) 76 qualified examiners (CAN/USD) false positive rate of 0.43% false negative rate of 0.0% Computer Based Methods Riva et al. – 3D measurements 7 vs 60 test shots fired Brand used affects same-source vs different source attribution NIST - Congruent Matching Cells (CMC) Pairwise comparison of small squares and distances Breechface and firing pin impressions Chen et al. – Congruent Matching Profile Segments (CMPS) Striation examination in segments Alsop et al. – Micro-CT Surface topography for depth and shape Repeatable, reliable and enough to discriminate Ballistic Imaging Database Firearms Misc. Reports Giverts et al. – Sounds Machine learning promising 3D printed firearms Discrimination between different weapons possible Some can have catastrophic failure Even when little metal present sufficient marks to identify Martin – Time since fire Measured temperature over time Steep decline found If temp high enough & measured quickly enough it was successful Ammunition DNA Reports Cartridge Successful if unfired Booth et al. recorded the first known case of DNA extracted from fired Prasad et al. – 17 Parts and cartridge Hammer, safety, cartridges, bullets, & cases worst for ID Malanio et al. – DNA from out-of-the-box ammo Found profiles from 93% of ammo boxes 3 different manufacturers Ammunition Fingermarks Reports Johnson – Print impressions on cartridges 150 deliberately placed – 68 identified 511 handled naturally – non identified Girelli & Segatto – Fingermark impressions from fired cartridges 1431 over a year Ridge detail was observed on 50 Only 5 sufficient Shooting Reconstruction Liscio et al. – 1.35 mm Sheet steel 2 rifles & eight pistols Photograph of bullet defect Nishshanka et al. – Hard surface interactions 2 concrete & 1 cement – Critical angles Kerkhoff et al. – Wood surface Critical angle not corelated to wood type Never measured wood density