Forensic Ballistics: Introduction

Ballistics Defined

• In its broadest sense, ballistics is the science of projectile motion.
• It involves the scientific study of knowledge, movement/mobility, and metallic/non-metallic objects propelled from firearms.
• In a narrow sense, it is about firearms identification through examining ballistics exhibits.
• Ballistics studies the conditions governing natural laws related to gunpowder and projectile performance in firearms.

Branches of Ballistics

• Ballistics has three branches: interior/internal, external/exterior, and terminal.
• Interior/Internal Ballistics
  • Focuses on what happens inside the gun.
  • It also deals with the properties/attributes of the projectile while still inside the gun.
  • Encompasses firing pin hitting the primer, ignition of the priming mixture, combustion of gunpowder, expansion of heated gas, pressure developed, energy generated, and recoil.
  • It includes bullet velocity inside the barrel, bullet rotation inside the bore, and cylindrical surface engraving.
• External/Exterior Ballistics
  • Focuses on bullet attributes and movement after leaving the gun muzzle.
  • Includes muzzle blast (noise from expanding gas), muzzle energy, trajectory (curved path of the bullet), range (straight distance between muzzle and target), accurate (effective) range (shooter's control distance), and maximum range (farthest projectile distance).
  • Also covers velocity (bullet speed per unit of time), air resistance, pull of gravity, and penetration depth.
• Terminal Ballistics
  • Branch of science dealing with the effects of projectile impact on the target.
  • Encompasses terminal accuracy (bullet grouping size), terminal energy/striking energy, and terminal velocity (bullet speed upon striking).

Forensic Ballistics

• Examination of fired firearms via recovered projectiles.
• Encompasses field investigation, laboratory/technical examination, and court testimony.
• Gun chronograph measures a projectile's velocity in flight.

Percussion Ignition

• Reverend Alexander John Forsyth is credited as the Father of percussion ignition, which uses percussion-sensitive explosive mixtures for new firing systems.
• Breech-loading arms using self-contained cartridges with needle-fire, pin-fire, rim-fire, and center-fire designs superseded percussion systems.
• The end of muzzle-loading arms began during this time.
• In 1842, the Prussian armed forces adopted the needle-fire system, proving effective in wars and conflicts from 1864-1870.
• Frenchman Lefaucheux made a pin-fire system gun and cartridge in 1836 with a projecting pin.

Firearms Defined

• According to the legal definition (Sec. 877 RAC/Sec. 290 NIRC), firearms include rifles, muskets, carbines, shotguns, pistols, revolvers, and deadly weapons using gunpowder/explosives.
  • The barrel makes a firearm complete for legal reasons.
• Technically, a firearm propels projectiles using expanding gases from burning gunpowder.
• It includes pistols/revolvers with barrels under 12 inches, rifles under 15 inches, shotguns under 24 inches, or any weapon designed to expel projectiles by explosives.

Handguns: Pistols vs. Revolvers

• A pistol has a short barrel and fires a single projectile through a rifled bore per trigger press.
• It's a handgun with a chamber integral to the barrel.
• A revolver is a hand firearm with a rotating cylinder for successively positioning cartridges for firing.

Other Firearms

• A repeating firearm which has a cylinder with multiple chambers and at least one barrel for firing.
• A submachine gun (SMG) is an automatic carbine for pistol cartridges, combining machine gun automatic fire with a pistol cartridge.
• The submachine gun has automatic or selective-fire action.
• Machine gun means any weapon which shoots or is designed to shoot automatically/semi-automatically, with more than one shot fired from one trigger pull.
• A machine pistol is an automatic pistol using the same functions as a semi-automatic.
• A lightweight automatic submachine gun fired from the hand.
• A RIFLE is designed to be fired from the shoulder, using the energy of the explosive in a fixed metallic cartridge to fire only a single projectile through the rifle bore for each pull of the trigger.
• A SHOTGUN is built to fire a number of lead pellets/shots in one cartridge from a smoothbore, breech-loading shoulder arm, also called a scattergun, pepper gun, or fowling piece.

Firearm Classifications

• Firearms can be classified based on gun barrel construction, caliber of projectile, and mechanical construction.
• Based on Gun Barrel Construction:
  • Smoothbore firearms lack rifling.
  • Rifled-bore Firearms have rifling.
• Based on Caliber of Projectile Propelled:
  • Artillery propels projectiles greater than one inch in diameter.
  • Small Arms propel projectiles less than one inch in diameter.
• Based on Mechanical Construction:
  • Single shot rifle has one firing chamber integral with the barrel which has to be manually loaded each time the weapon is fired.
  • Repeating arms are manually loaded.
    • Bolt action types extract and eject cartridges then insert new ones when cocking the gun.
    • Automatic loading fires, extracts, ejects, reloads, and cocks with each trigger pull via gas or recoil pressure, as well as requires you to release the trigger and pull again after each shot.
    • Slide action loads by forward-backward manipulation of the under forearm.
    • Lever action loads when releasing the top catch to swing the barrel down.

Categories of Small Arms

• Handguns is a firearm designed to be held and operated by one hand.
  • Single-shot pistols are limited to one shot per firing cycle and must be manually emptied/reloaded; often of break type style.
  • Multi-barreled pistols have more than one barrel which increases firing rate/hit probability and reduces barrel erosion/overheating.
  • Derringers are small pocket firearms without a magazine/cylinder, having multiple barrels loaded/fired separately, and traditionally have no trigger guard.
  • Revolvers have a revolving cylinder containing chambers, being either single-action or double-action.
    • Swing-out revolvers swing out the cylinder by pressing the cylinder latch.
    • Break-top revolvers swing down the barrel and cylinder by releasing the top catch.
    • Solid-frame revolvers, the oldest form, features the cylinder held by a pin.
  • Semi-automatic pistols are handguns using a single chamber but automatically remove empty casings and insert new cartridges.
    • The first commercial automatic pistol was produced by Borchardt in 1893 to be the predescessor to the Luger.
• Automatic pistols have four methods of operation:
  • Blow-back means gas pressure forces an unlocked slide to the rear for extraction, ejection, and reloading.
  • Delayed or retarded blow-back directs propellant gas into a cylinder to delay the slide.
  • Recoil locks the barrel and slide together until the bullet leaves the barrel.
  • Gas uses high-pressure gas to power a mechanism for extracting spent cases and chambering new cartridges.
• Modes of Operation
  • Single action (SA)
  • Double action (DA)
  • Double action Only (DAO)
• Rifles has rifled barrels and are designed to be fired from the shoulder.
  • Automatic rifles use gas pressure or recoil to eject the fired case, load the next round, fire, and eject.
  • An "assault rifle" is auto-loading and capable of full-automatic fire, has a large-capacity (20+ rounds) detachable magazine, and fires an intermediate rifle cartridge.
• Shotguns are intended for shoulder firing, have a smooth bore, and are designed to fire multiple pellets.
• Shotguns are classified as single shot or double barrel (over/under or side-by-side).
  • Bolt-action, Lever-action, Pump-action, Auto-loading, or Automatic
• Submachine guns (SMG) are designed for shoulder/hip firing, capable of being fully automatic and have a rifled barrel dedicated to firing pistol rounds.
• Machine guns can provide fully automatic firing, doing so with fire rifle ammunition.
• Gatling guns is one of the best known early rapid-fire weapons and a forerunner of the modern machine gun.
  • Their operation centered on a cyclic multi-barrel design which facilitated cooling and synchronized the firing
• Machine Gun Classifications:
  • Light machine gun (LMG) is for individual soldiers as infantry support, often serving as squad automatic weapons.
  • Medium machine gun (MMG) typically refers to a belt-fed automatic firearm that fires a full-power rifle cartridge.
  • Heavy machine gun (HMG) for example, .50 or 12.7mm types pioneered by John Moses Browning are designed for increased range, penetration and destructive power.

Multi-barrel Firearms & Ammunition

• Multi-barrel firearms consists of several barrels designed to increase the chances of hitting fast moving targets.
• According to Sec. 877 RAC, ammunition is a loaded shell for rifles, muskets, carbines, shotguns, revolvers, and pistols that fires a missile by explosives.
• A cartridge is a complete unfired unit with a bullet, case, gunpowder, and primer.
• Catridge parts: bullet, catridge case, gunpowder, primer.

Cartridge Classifications

• Cartridges classification can be based on the primer's location and caliber
• Based on the primer's location
  • Pin-fire has a pin
  • Rim-fire has a rim
  • Center-fire has a center
• Different Calibers
  • Cal .223 - 5.56mm
  • Cal .25 - 6.35mm
  • Cal .30 - 7.62mm
  • Cal .32 - 8.128mm
  • Cal .354 - 9.0mm
  • Cal .357 - 9.067mm
  • Cal .38 - 9.65mm
  • Cal .380 - 9.65mm
  • Cal .40 - 10.16mm
  • Cal .44 - 11.17mm
  • Cal .45 - 11.43mm

Bullets

• A bullet is a metallic or non-metallic projectile propelled from a firearm via burning gunpowder.
• Bullet classifications is based on mechanical construction:
  • Lead bullets are made of lead alloys, and lean tin and antimony.
  • Jacketed bullets have a lead alloy core covered by a harder metal jacket. based on form and shape:
  • Wad-cutter
  • Flat noise
  • Pointed
  • Semi-wad
  • Hollow point
  • Soft point (dum-dum bullet)
  • Round nose
  • Hollow base
• Bullet Parts:
  • Nose or ogive
  • Cannelure - Holds lubricant
  • Base
  • Knurling - Holds the jacket or serves as the manufacturer's mark

Catridge Case

• A cartridge case is a tubular container holding the bullet, gunpowder, and primer.
• Catridge cases serve to unitize components and waterproof gunpowder
• Case Parts:
  • Rim - for limiting forward travel into chambers
  • Head and Body - constitute the cork that plugs the breech of the barrel
  • Neck - part of the cartridge case that is occupied by the bullet.
  • Shoulder - which supports the neck
  • Cannelures - grooves for preventing bullets from being pushed back
  • Crimp - part which is a tuned in upon the bullet, as well as, aids in holding the bullet in place
    • Roll Crimp - where the case is rolled into the bullet
    • Taper Crimp - used primarily with cartridge.
    • Stab or Ring Crimp - used only in jacket ammunition

Other Catridge Components

• Extracting grooves are circular grooves at the case base for automatic withdrawal.
• The base is the bottom portion housing the primer and shell head
• The primer pocket performs triple functions which includes securely holding the primer,preventing gas escape and, acting as a solid support for primer anvils. There are two types of primer pockets:
  • Berdan has two flash holes (primers are traditionally loaded with. Has no integral anvil, meaning it forms a projection in the primer pocket.
  • Boxer has a single flash hole in the bottom of the case.
  • Vents are connecting holes between the primer and gunpowder.
• Three General Shapes of Cartridge Cases:
  • Straight cartridge cases have no visible neck and are commonly used in pistols and revolver.
  • Bottleneck designs allow for more powder in a shorter cartridge, often found amongst rifle cartridges.
  • Tapered cartridges, considered obsolete, was present in the "magnum jet" cartridge in caliber .22.
• Cartridge Classification according to Head Form:
  • Rimmed cartridges have an extractor flange larger than the case body.
  • Semi-rimmed cartridges have an extractor flange that is larger in diameter than the cartridge case body, but they also have a groove around the case body just in front of the flange.
  • Rimless extractor flange with the same diameter as the cartridge case body.
  • Rebated has an exterior flange smaller than the case with a groove.
  • Belted cartridges is a small band around the case head, forward of the extractor groove.
• Marks Found on Fired Shells: firing pin mark, breech face mark, extractor mark, ejector mark, chamber mark, pivotal mark, magazine lip mark and shearing mark.

Primer

• The primer consists of a brass/gilding metal cup which, contains a highly sensitive chemical mixture that detonates/ignites
• Primer Parts: primer cup, priming mixture, anvil, disc.
• The Two Fold Purpose of the Disc is to hold the priming mixture in place and to exclude moisture.

Gunpowder

• Gunpowder which includes either propellant or powder charge is what propels the bullet through the barrel!
• Gunpowder Classifications:
  • Black powder is the oldest propellant that consists of irregular grains while creating grayish smoke and residue.
  • Smokeless powder is the most commonly used powder in modern ammunition, being the most powerful and effective propellant!
• Four Main Classes of Smokeless Gunpowder:
  • Single-base propellant contains nitroglycerine geletanized with nitrocellulose.
  • Double-base propellant includes nitrocellulose and nitroglycerine, centralite, vaseline phthalate esters, and inorganic salts.
  • Triple Base propellant includes nitrocellulose, nitroglycerine and Nitro-guanidine,
  • High-Ignition propellant which, its main constituents is from RDX group of high explosives in conjunction of Heckler and Koch for the lather's G11K2 rifle. This is caseless ammunition.

Toolmarks

• Is a mark resulting from direct contact between a tool and the surface of some object.
• Two Types of Toolmarks
  • Indented Mark is made by forcing a tool against an object, which leads to a negative impression.
  • Straited Mark appears when pressure is applied and the tool is moved across a softer surface.

Firearms Identification

• This is the process of analyzing bullets and cartridge cases from crime scenes to determine what type of firearm was used.
• Four methods commonly used in making the rifling:
  • Scrape Cutter consists of a thin, slightly smaller rod, into which is a set either one or two curved hardened steel scrapers
  • Hook Cutter means a cutter with the general shape of a crochet-hook that is set into a recess or slot in a rod
  • Broaching Method consists of a rod upon which there are 25 to 30 hardened steel rings
  • Swaging or Button Methods consists of a "plug” of extreme hardness

Marks Found on Bullets

• Land Marks - cause by the lands inside the barrel
• Groove Marks - cause by the grooves inside
• Skid or Slippage Marks - jumping the rifling
• Stripping Mark - moving with a motion of transition
• Marks made by Forcing Cone- when the bullet strikes the forcing cone
• Class Characteristics is the common to a group of firearms.

Firearms: Characteristics

• Bore Diameter
• Number of lands and grooves
• Directions of rifling twist - left and right hand twist.
• Widths of lands and grooves
• Degree of twist of rifling (Pitch)
• Depth of grooves
• Individual characteristics are unique to a particular firearm, likely to be repeated.
  • Firearms identification is actually a refined toolmark identification.
  • Natural wear and tear of the tools are involved.

Firearms Identification: Principles

• A softer surface comes in contact with a harder surface, where the softer surface will acquire impressions/scratches.
• No two things are absolutely identical or alike

Instruments Used in Firearms Identification

• Comparison Microscope consists of two microscopes connected by an optical bridge that, allows two objects to be viewed at the same time
• Onoscope – inserted through the barrel

Other Tools

• Caliper is used to measure the caliber of a firearm
• Micrometer – is used to measure the caliber of a bullet and cartridge cases
• Stereoscopic microscope is used for preliminary examination
• Electric gun marker - marks evidence
• Trigger pull devise - determines the pounds of pressure necessary to activate the trigger.
• Cartridge Case Identification

Cartridge Cases: Marks

• Firing Pin
• Breech face
• Extractor
• Ejector
• Clip Marks
• Shearing Marks
• Chamber-produced