1 Frensic Science: Fundamentals & Investigatins, 2e Cengage/NGL/Suth-Western 2016
Firearms and Ballistics By the end f this chapter yu will be able t: 18.1 Cmpare and cntrast the different types f firearms, including handguns, rifles, and shtguns. 18.2 Put in rder the sequence f events that result in a firearm discharging. 18.3 Estimate the trajectry f a prjectile. 18.4 Discuss the cmpsitin and frmatin f gunsht residue and its reliability as a surce f evidence. 18.5 Cmpare and cntrast entrance and exit wunds, including size, shape, gunsht residue, and the presence f burns. 2 Frensic Science: Fundamentals & Investigatins, 2e Cengage/NGL/Suth-Western 2016
Firearms and Ballistics By the end f this chapter yu will be able t: 18.6 Distinguish amng the varius frms f firearms evidence, including rifling, markings n cartridges, marks n prjectiles, and gunsht residue. 18.7 Discuss hw technlgy has imprved the ability t btain, cmpare, analyze, stre, and retrieve firearm and ballistics evidence. 18.8 Prcess and/r analyze a crime scene fr firearm and ballistics evidence. 3 Frensic Science: Fundamentals & Investigatins, 2e Cengage/NGL/Suth-Western 2016
Vcabulary ballistics lands and grves breech pistl bullet revlver caliber rifle cartridge rifling firearm trajectry gunsht residue (GSR) 4 Frensic Science: Fundamentals & Investigatins, 2e Cengage/NGL/Suth-Western 2016
Intrductin Types f ballistic evidence that can be used t help slve a crime include: Guns used in a crime Spent cartridges Bullets embedded in a murder victim 5 Frensic Science: Fundamentals & Investigatins, 2e Cengage/NGL/Suth-Western 2016
Histry f Gunpwder and Firearms Mre than 1000 years ag, the Chinese invented gunpwder. In 14th-century Eurpe, inventrs learned they culd direct the explsive frce f gunpwder dwn a cylinder t mve a deadly prjectile. The earliest firearms, which date back t 1475, had wicks t carry a flame t the gunpwder. 6 Frensic Science: Fundamentals & Investigatins, 2e Cengage/NGL/Suth-Western 2016
Histry f Gunpwder and Firearms (cntinued) At the beginning f the 1600s, flintlck firearms began t be used. Arund 1820, percussin-cap firearms replaced flintlck firearms. 7 Frensic Science: Fundamentals & Investigatins, 2e Cengage/NGL/Suth-Western 2016
Lng Guns and Handguns Lng guns require the use f tw hands. Rifles Fire bullets Shtguns Fire either small rund pellets r a single prjectile Handguns can be fired with ne hand. Pistls (revlvers) Semiautmatic firearms 8 Frensic Science: Fundamentals & Investigatins, 2e Cengage/NGL/Suth-Western 2016
9 Frensic Science: Fundamentals & Investigatins, 2e Cengage/NGL/Suth-Western 2016
Firearms and Rifling Each rifled gun barrel is unique. As a gun is fired, the barrel marks the bullets with its wn unique pattern. 10 Frensic Science: Fundamentals & Investigatins, 2e Cengage/NGL/Suth-Western 2016
Bullets and Cartridges The cartridge cntains: Primer pwder Gunpwder The bullet The casing material that hlds them altgether 11 Frensic Science: Fundamentals & Investigatins, 2e Cengage/NGL/Suth-Western 2016
Bullets and Cartridges (cntinued) Anatmy f a Cartridge Bullet Primer pwder Headstamp 12 Frensic Science: Fundamentals & Investigatins, 2e Cengage/NGL/Suth-Western 2016
Bullets and Cartridges (cntinued) The headstamp n the bttm f the cartridge casing identifies: The caliber The manufacturer 13 Frensic Science: Fundamentals & Investigatins, 2e Cengage/NGL/Suth-Western 2016
Hw a Firearm Wrks When the trigger is pulled, the primer pwder mixture ignites. The primer pwder mixture delivers a spark t the gunpwder supply. The pressure f the expanding gases prpels the bullet frm the casing and int the barrel. The bullet exits the barrel. 14 Frensic Science: Fundamentals & Investigatins, 2e Cengage/NGL/Suth-Western 2016
15 Frensic Science: Fundamentals & Investigatins, 2e Cengage/NGL/Suth-Western 2016
Caliber f a Cartridge The caliber is a measure f the diameter f the bullet. Hundredths r thusands f an inch The Eurpean methd f naming firearm caliber uses the metric system fr measurement f bullet diameter. Nine-millimeter firearms fire 9 mm bullets. 16 Frensic Science: Fundamentals & Investigatins, 2e Cengage/NGL/Suth-Western 2016
17 Frensic Science: Fundamentals & Investigatins, 2e Cengage/NGL/Suth-Western 2016
Evidence frm Bullets and Cartridges T cmpare the markings n an evidence bullet t the markings n a suspected firearm barrel, a firearm examiner can testfire similar bullets frm the suspected firearm int a water tank r gel blck. Ballistics sap can be used t determine the yaw damage caused by a bullet. Ballistics gel retains the path f a fired bullet. 18 Frensic Science: Fundamentals & Investigatins, 2e Cengage/NGL/Suth-Western 2016
19 Frensic Science: Fundamentals & Investigatins, 2e Cengage/NGL/Suth-Western 2016
Marks n Spent Cartridges Firing pin marks Breechblck markings Extractr and ejectr marks 20 Frensic Science: Fundamentals & Investigatins, 2e Cengage/NGL/Suth-Western 2016
21 Frensic Science: Fundamentals & Investigatins, 2e Cengage/NGL/Suth-Western 2016
Gunsht Residue Gunsht residue can adhere t the persn hlding the firearm, leaving evidence n him r her. In clse-range shtings, sme GSR may be depsited n the victim. 22 Frensic Science: Fundamentals & Investigatins, 2e Cengage/NGL/Suth-Western 2016
23 Frensic Science: Fundamentals & Investigatins, 2e Cengage/NGL/Suth-Western 2016
Evidence frm Spent Bullets and Wunds Generally, entrance wunds are smaller than exit wunds. If a bullet penetrates clthing first, fibers may be embedded in the wund, indicating the directin f penetratin. If the bullet is fired when the muzzle is in cntact with the skin, flash burns t the skin may result. Radial tears in the skin ccur if the gunsht is directly ver bne. Beynd fur feet, nly a bullet hle is visible. 24 Frensic Science: Fundamentals & Investigatins, 2e Cengage/NGL/Suth-Western 2016
25 Frensic Science: Fundamentals & Investigatins, 2e Cengage/NGL/Suth-Western 2016
Gravity and Trajectry 26 Frensic Science: Fundamentals & Investigatins, 2e Cengage/NGL/Suth-Western 2016
Using Trajectry t Estimate the Lcatin f a Shter 27 Frensic Science: Fundamentals & Investigatins, 2e Cengage/NGL/Suth-Western 2016
Databases Natinal Integrated Ballistic Infrmatin Netwrk (NIBIN) A cmbined database f the FBI and the Bureau f Alchl, Tbacc, Firearms, and Explsives cntaining: Firearms and prjectiles databases Firearm "fingerprints" 28 Frensic Science: Fundamentals & Investigatins, 2e Cengage/NGL/Suth-Western 2016
Ballistics Evidence Standards The Organizatin f Scientific Area Cmmittees (OSAC) Crdinates standards t imprve the reliability f frensic science evidence including digital images f the firearm fingerprint 29 Frensic Science: Fundamentals & Investigatins, 2e Cengage/NGL/Suth-Western 2016
Summary Ballistics is the study f the mechanics f the launching, flight, and behavir f fired prjectiles. Mdern firearms are divided int tw basic types lng guns and handguns that require tw hands r ne, respectively, fr accurate firing. Handguns can be classified as revlvers r semiautmatic firearms, depending n the lading mechanism. Bullets fired frm a firearm shw patterns f lands and grves that can be cmpared with the rifling pattern in the barrel f the firearm. 30 Frensic Science: Fundamentals & Investigatins, 2e Cengage/NGL/Suth-Western 2016
Summary (cntinued) A cartridge cnsists f primer pwder, gunpwder, a bullet, and the casing material that hlds them all tgether. The caliber f a cartridge is the diameter f its bullet and is included with the name f the manufacturer n the headstamp. In additin t examining lands and grves n a bullet, investigatrs can examine firing pin marks, breechblck marks, and extractr and ejectr marks n a spent cartridge t cmpare evidence at a crime scene with a specific firearm. Gunsht residue n shters can help investigatrs identify a suspect. 31 Frensic Science: Fundamentals & Investigatins, 2e Cengage/NGL/Suth-Western 2016
Summary (cntinued) Investigatrs can use databases, such as the natinal database NIBIN, t cmpare crime-scene evidence t evidence cllected frm previus crimes. Using at least tw reference pints, an investigatr can recreate a bullet s trajectry and estimate the lcatin f the shter. Advances in technlgy, including cmparisn micrscpes and mass spectrmetry, have imprved the ability f firearms and ballistics experts t cmpare crime-scene evidence with test-fired prjectiles and GSR analysis. 32 Frensic Science: Fundamentals & Investigatins, 2e Cengage/NGL/Suth-Western 2016