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Chapter 17 BallisticsBy the end of this chapter you will be able to:oExplain the differences between a handgun, arifle, and a shotgunoDescribe rifling on a gun barrel and how itaffects the flight of the projectileoExplain barrel size and caliberAll Rights Reserved South-Western / Cengage Learning 2012, 20091Forensic Science: Fundamentals & Investigations, Chapter 17
Chapter 17 BallisticsBy the end of this chapter you will be able to:2oDescribe how bullets are test fired and matchedoDiscuss the role of ballistics recovery andexamination at a crime sceneoDetermine the position of the shooter based onbullet trajectoryForensic Science: Fundamentals & Investigations, Chapter 17
1. DefineBallisticso3The study ofprojectiles(bullets) andfirearmsForensic Science: Fundamentals & Investigations, Chapter 17
2. Define Firearmo4A weapon capable of firing a projectile usinga confined explosive as a propellant.Forensic Science: Fundamentals & Investigations, Chapter 17
IntroductionBallistic evidence helps explain:oWhat type of firearm was usedoThe caliber of the bulletoThe number of bullets firedoWhere the shooter was locatedoWhether a weapon was fired recentlyoIf a firearm was used in previous crimes5Forensic Science: Fundamentals & Investigations, Chapter 17
3. History ofGunpowder and Firearmsooo6Chinese inventedgunpowder over athousand years ago;used it for fireworks14th century Europe –directed gunpowderdown cylinder to fire aprojectileMatchlock weapons –used wick to carry flameto gunpowderForensic Science: Fundamentals & Investigations, Chapter 17
3. History ofGunpowder and Firearmsoo7Flintlock – used sparks from a chip of flint; allowed to firein wet weatherMuzzle-loading – user puts gunpowder and projectiledown the barrel
3. History ofGunpowder and Firearmsoo8Cartridge and breechloading; percussion firingRevolver, semiautomatic, andautomatic handguns
5. Long Guns and HandgunsLong gunso o(6&7) Two typesA.B.9Use 2 hands to fire accuratelyLonger barrel makes shots moreaccurateRifles fire bullets; wound will besmall, roundShotguns fire pellets (shot) or asingle projectile (slug); wounds fromshot will be small , superficial, andwidespread; from slug much largerand deep.Forensic Science: Fundamentals & Investigations, Chapter 17
5. Long Guns and HandgunsoHandguns – 2 typesA.10Pistols are fired withone hand; 10 or morecartridges are held inclip or magazineForensic Science: Fundamentals & Investigations, Chapter 17
5. Long Guns and HandgunsoHandguns – 2 typesB. Revolvers – also withone hand; have acylinder that holdsusually six cartridges;first invented by SamuelColt11Forensic Science: Fundamentals & Investigations, Chapter 17
Parts of a Hand Gun12Forensic Science: Fundamentals & Investigations, Chapter 17
Parts of a Hand Gun13Forensic Science: Fundamentals & Investigations, Chapter 17
Bullets, Cartridges, and CalibersooCartridge—a case that holdsa bullet, primer powder, andgunpowderThe bullet, usually of metal, isout front with the cartridge,holding the primer andpropellant powders, behind.Bullet TipFlashhole14Forensic Science: Fundamentals & Investigations, Chapter 17
Caliber of the Cartridgeoooo15Caliber—a measure of the outside diameter of thecartridge; also measure of inside diameter of barrelIn hundredths of an inch or millimetersCommon calibers in hundredths of an inch include.22, .25, .357, .38, .44, and .45Why should the caliber of ammunition match thefirearm that shoots it? If they do not match, whatcould go wrong?Forensic Science: Fundamentals & Investigations, Chapter 17
Classification of gunsooo16Semiautomatic weapons – fire only one bulletper pull of the triggerFully automatic – fire repeatedly as long astrigger is pressed.In both, empty cartridge ejects (often can befound at crime scene) and next cartridgeadvances automatically.Forensic Science: Fundamentals & Investigations, Chapter 17
How a Firearm Works1. After trigger pull, thefiring pin hits thebase of the cartridge,igniting the primerpowder2. The primer powder sparks through the flash hole tothe main propellant supply17Forensic Science: Fundamentals & Investigations, Chapter 17
How a Firearm Works3. The pressure of theexplosion pushes thebullet from the casinginto the barrel4. The bullet follows the lands and grooves spiraling outof the barrel18Forensic Science: Fundamentals & Investigations, Chapter 17
Energy causing the bullet to fireo19Smarter every day videoForensic Science: Fundamentals & Investigations, Chapter 17
Physics outside of the barreloo20Yaw refers to therotation of the noseof the bullet awayfrom the line offlight.Precession refersto rotation of thebullet around thecenter of mass.Forensic Science: Fundamentals & Investigations, Chapter 17
Firearms and Riflingooo21Grooves and ridges(lands) in the barrel of agun produce the twistingthat adds accuracyThis leaves a pattern onthe bullet that is uniqueRifiling videoForensic Science: Fundamentals & Investigations, Chapter 17
Rifling adds accuracy22Forensic Science: Fundamentals & Investigations, Chapter 17
Firearms and Riflingo23Ridges (lands) within the barrel willleave grooves on the bullet.Forensic Science: Fundamentals & Investigations, Chapter 17
The Study of Bulletsand Cartridge CasingsHow is each fired bullet marked?2. What is the procedure to match a spent bullet tothe firearm that shot it?3. What makes up a test-firing, and why is it done?1.24Forensic Science: Fundamentals & Investigations, Chapter 17
Projectile Motiono25Projectile motion is an example of curved motionwith constant acceleration. It is two dimensionalmotion of a particle thrown obliquely into the air.Forensic Science: Fundamentals & Investigations, Chapter 17
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Projectile Motion2 main forces acting on a fired projectileHorizontalaccelerationdue to rapidlyexpanding air27Forensic Science: Fundamentals & Investigations, Chapter 17Verticalacceleration dueto gravity (-) andinitial aim ( /-) ofthe barrel
Projectile Motion28Forensic Science: Fundamentals & Investigations, Chapter 17
Projectile Motiono29Which falls first? A fired bullet or a droppedbulletForensic Science: Fundamentals & Investigations, Chapter 17
Trajectoryoo30Two reference points are needed to define thetrajectoryInvestigators canfigure the shooterdischarged thefirearm somewherealong that lineForensic Science: Fundamentals & Investigations, Chapter 17
TrajectoryoReference points can be bullet holes in objects or victims An entry point and exit point on a victim Gunshot residue or spent cartridge casingso31Lasers can trace a straight-line path todetermine the position of the shooterForensic Science: Fundamentals & Investigations, Chapter 17
FBI Handbook on Firearm Examinations1. BulletsDetermine caliber, rifling impressions, and bulletmanufacturer Microscopic characteristics can be compared withtest-fired bullets for an associationComparison Microscope – allows viewing of twodifferent objects side-by-sidedeveloped by Calvin Goddard – Father of Ballistics 32Forensic Science: Fundamentals & Investigations, Chapter 17
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FBI Handbook on Firearm Examinations2. Cartridge cases or Shotshell casingsDetermine caliber or gauge, manufacturer, andwhether there are marks of value for comparisonNIBIN – National Integrated Ballistic InformationNetwork; ran by ATF - Bureau of Alcohol, Tobacco,Firearms and Explosives o35Forensic Science: Fundamentals & Investigations, Chapter 17
Marks on theSpent Cartridge CasingsoFiring pin marks appear on the rim or center of thespent cartridge can be used to match a cartridge to afirearmoBreechblock marks produced when the cartridge casingslams backward and strikes thebreechblockoo36Extractor marksEjector marksForensic Science: Fundamentals & Investigations, Chapter 17
FBI Handbook on Firearm Examinations3. Unfired Cartridges or Shotshells 37Determine the caliber or gauge and whether thereare marks of value for comparisonCan determine if ammunition was ever loaded inand extracted (extractor marks) from a specificfirearmAlso look for manufacturing marksForensic Science: Fundamentals & Investigations, Chapter 17
FBI Handbook on Firearm Examinations4. Shot Pellets, Buckshot, or Slugs Determine size of the shot, gauge of the slug, andmanufacturer5. Wadding 38Determine the gauge and manufacturerForensic Science: Fundamentals & Investigations, Chapter 17
FBI Handbook on Firearm Examinations5. Gunshot Residues (GSR) Particles of unburned powder and traces of smoke Leave traces on the hand, arm, face, hair, or clothingof the shooter and/or victimoo39Chemical testing can detect residue even ifremoval is attemptedDistance from victim to shooter can bedetermined by examining the residue pattern onthe victimForensic Science: Fundamentals & Investigations, Chapter 17
FBI Handbook on Firearm Examinations6. Gun Parts Can determine caliber and model of a gun fromwhich the parts originated7. Silencers 40Test if muzzle attachment can be classified as asilencerForensic Science: Fundamentals & Investigations, Chapter 17
Bullet Woundso Why do entrance wounds tend to be smaller than exitwounds? The skin is somewhat elastic and & stretchesas bullet enters. As bullet moves through the body, itmay collect and carry body tissue and bone with it.o If the bullet penetrates clothing, what can fibersembedded in the wound indicate? Point to the directionof penetration.o Where is gunshot residue usually found? GSR isusually found near entrance wound.41Forensic Science: Fundamentals & Investigations, Chapter 17
Bullet Woundso If the gun is fired with the muzzle touching the victim’sskin, what telltale mark may show up? Hot gasesreleased from the muzzle flash may burn the skin,leaving a telltale mark.o Will larger or will smaller caliber bullets tend to lodgewithin the body rather than passing through? Why?Smaller caliber tend to lodge within the body, whilelarger caliber bullets will pass through.42Forensic Science: Fundamentals & Investigations, Chapter 17
. . . . . . . . . . . . . Summary . . . .ooooo43Ballistics is the study of bullets and firearms.Firearms are divided into two groups—long gunsand hand guns.Fired bullets show patterns of lands and groovesthat match the rifling pattern in the barrel.A cartridge consists of primer powder, gunpowder,a bullet and the casing material.The caliber of a cartridge usually is a measure ofits diameter.Forensic Science: Fundamentals & Investigations, Chapter 17
. . . . . . . . . . . . . . . . . Summaryoooo44Investigators also check for firing pin, breechblock,extractor, and ejector marks.Gunshot residue can help recreate a crime.Using at least two reference points, an investigatorcan recreate a bullets trajectory and determinewhere the shooter was located.Examining body wounds can determine where abullet entered and exited the victim.Forensic Science: Fundamentals & Investigations, Chapter 17
39 Forensic Science: Fundamentals & Investigations, Chapter 17 5. Gunshot Residues (GSR) Particles of unburned powder and traces of smoke Leave traces on the hand, arm, face, hair, or clothing of the shooter and/or victim o Chemical testing can detect residue even if removal is attempted o Distance from victim to shooter can be determined by examining the residue pattern on
