Ballistics Dr. Walker.

Ballistics Dr. Walker

Ballistics Ballistics Forensic Ballistics
Write all Ballistics Ballistics Science that deals with the motion, behavior, and effects of projectiles (bullets, rockets, missiles) Forensic Ballistics Scientific analysis and interpretation of evidence related to the illegal use of firearms Deals with motion, behavior, and effects of a bullet fired from a gun

Ballistic Properties Velocity Kinetic Energy Trajectory Speed
Write all Ballistic Properties Velocity Speed Kinetic Energy Energy due to motion Trajectory Flight path of bullet

Back to Explosives… Black Powder Invented 1000 years ago in China
Write all Back to Explosives… Black Powder Invented 1000 years ago in China Consists of Potassium nitrate (KNO3) Charcoal (carbon) Sulfur

History Black Powder Wasn’t used in guns until the 14th century.
Write all History Black Powder Wasn’t used in guns until the 14th century. First projectile weapons using gunpowder were cannons Were not accurate

Write all Cannons Metal tube with a closed end and an open end. The closed end has a small fuse hole. Bore – open end of the cannon Breech – rear part of the bore (cannonball and powder sit here) Fuse – length of flammable material Runs from outside cannon to gunpowder

Why guns work Black Powder is ignited by a source
Write all Why guns work Black Powder is ignited by a source Source depends on weapon Chemical reaction causes formation of large amount of gas Pressure from the buildup of gas forces the projectile (bullet, cannonball, etc.) from the weapon

Write all The next step The next step -- when projectile weapons were made small enough for one person to handle. Long guns: Guns that needed two hands (and possibly a wooden support) to handle. Handguns: Guns that could be used with one hand.

Loading Early Guns Muzzleloaders
Write bold Loading Early Guns Muzzleloaders Weapons that are loaded by putting the powder and the lead ball into the firing end (or muzzle) of the gun. The gun is fired by a flint held in a vise striking metal, creating hot sparks that ignite the black powder in the flash pan.

Lack of Accuracy Early guns were not accurate
Write all Lack of Accuracy Early guns were not accurate Random spin on projectile Random spin, random trajectory Initial attempts to improve the accuracy of guns – lengthening the barrel Made them harder to carry

Another Strategy The principle behind a shotgun
Write all Another Strategy The principle behind a shotgun Firing multiple projectiles made it more likely one of them would hit something. The projectiles from a shotgun move out in a widening circle, giving the shooter a better chance of hitting the target. The projectiles still have a random spin.

Gauge Gauge The diameter of a shotgun barrel
Write bold Gauge Gauge The diameter of a shotgun barrel Originally measured by how many lead balls weighing a total of 1 lb could fit into the diameter of the shotgun barrel. For example: 12 lead balls (1/12 lb) could fit into the barrel of a 12 gauge shotgun. The actual diameter of a shotgun barrel actually decreases as the gauge increases.

Modern Physics and Guns
Write bold Modern Physics and Guns It was discovered that spinning a projectile in a direction perpendicular to the flight plan (like the spiral of a football) causes it to travel in a straight line. Sometime in the 15th century, gun manufacturers started putting grooves in the smooth bores of musket barrels.

Modern Physics and Guns
Write bold Modern Physics and Guns The grooves that twist as they run the length of the barrel are called rifling. It is the rifling of the barrel that distinguishes a rifle from a musket or shotgun Military weapons did not contain rifling until the 19th century

Rifling

Caliber Land – the original, raised surface of the barrel
Write all Caliber Land – the original, raised surface of the barrel Groove – the interior of the barrel where metal has been cut away. The caliber is the inside diameter of a gun barrel from land to land.

Caliber of Weapons Land to Land Diameter Caliber 0.22 in 22 0.357 in
44 0.45 in 45 9 mm (0.35 in) 9 mm

Rifle and Handgun Calibers

Handguns

Revolvers A revolver uses a cylinder or wheel to hold the ammunition.
Write all Revolvers A revolver uses a cylinder or wheel to hold the ammunition. Each time the trigger is pulled, a new round is rotated into the firing position. Two types Single-action revolver needs to have the hammer pulled back each time it is fired. Double-action revolver, the hammer is pulled back automatically each time the trigger is pulled.

Revolvers Less accurate
Write all Revolvers Less accurate Has weak points that allow gases to escape causing…. Slower muzzle velocity and less range

Semi-Automatic Weapons (Pistols)
Write all Semi-Automatic Weapons (Pistols) Contains slide on top of firearm Magazine – holding device for bullet cartridge Loaded into handle of pistol For semi-automatic weapons, single and double action refers to the same information Single – requires the slide to be pulled back Double – squeezing the trigger pulls the slide back automatically

Advantages of Pistols Magazines carry more bullets Faster firing rates
Write all Advantages of Pistols Magazines carry more bullets rounds per magazine, 6 for revolver Faster firing rates Faster reloading Single magazine versus individual rounds in revolver

Semi-Automatic Weapons

Rifles Designed to be fired from the shoulder, as opposed to a handgun
Write all Rifles Designed to be fired from the shoulder, as opposed to a handgun

Types of Rifles Bolt Action Automatic

Write all Bolt-Action Rifles Characterized by a handle on the side that allows the user to extract a spent cartridge and place a new one into the barrel from the magazine by sliding the bolt back into place

Bolt-Action Rifles Longer cartridges than in a handgun More gunpowder
Write all Bolt-Action Rifles Longer cartridges than in a handgun More gunpowder Higher muzzle velocity and kinetic energy Muzzle velocity Standard issue .40 caliber pistol = 305 m/s Police sniper .308 bolt-action rifle = 792 m/s

Bolt-Action Rifles Flatter trajectory than pistols
Write all Bolt-Action Rifles Flatter trajectory than pistols Increases comparable range When fired parallel to ground Pistol range about 200 yards Some high caliber rifle ammo: range = 5 miles!!

Automatic Rifles Also known as assault rifles
Write all Automatic Rifles Also known as assault rifles Can fire a continuous stream of bullets with each pull of the trigger Accurate up to yards Most common models AK-47 (Russian), M-16 (US Military), AR-15 (Law enforcement)

Shotguns Contain no rifling Inside of barrel is smooth
Write all Shotguns Contain no rifling Inside of barrel is smooth Spray of multiple projectiles Minimal control over path Increasing area of coverage increases chance of hitting a target

Shotguns Effective range of buckshot shells = 60 – 100 feet
Write all Shotguns Effective range of buckshot shells = 60 – 100 feet Slug – lead bullet about the size of a thumb Effective range = 300 feet Very powerful at short distances

Shotguns Break action Pump action Hinged where barrel and chamber meet
Write all Shotguns Break action Hinged where barrel and chamber meet Pump action Contain movable slide (fore-end) Ejects anything in chamber, cocks hammer, and moves new shell into chamber

Shotguns Break-Action Pump Action

Sawed-Offs Shortened to 18 inches or less by….sawing off the end
Write all Sawed-Offs Shortened to 18 inches or less by….sawing off the end Why do this? Easier to conceal Less recoil More spread of ammo Illegal in most circumstances

Write bold Shotgun Evidence The pellets from shotguns do not come in contact with the barrel of the shotgun. They are held in a plastic cup or sleeve until they exit the gun barrel. The pellets don’t pick up any striations that can be used to tell from which barrel they were fired. The diameter of a pellet can be measured to determine the type of shotgun ammunition used (birdshot, buckshot, etc.)

Shotgun Evidence Rule of Sixes
Write all Shotgun Evidence Rule of Sixes Used to estimate the distance for a shotgun wound. Six feet or less—the wound appears as a single, round hole. Distance < 6 yds, the wound appears as a central hole with many small pellets around it. Distance > 6 yds, the wound appears as a series of small pellet holes.

Average Velocity Velocity Distance/Time V = D/T Solve “Plug and Chug”
Write all Average Velocity Velocity Distance/Time V = D/T Solve “Plug and Chug” Put in known, solve for unknown

Write all Manufacturing Specific tools are required to cut grooves into the metal of a barrel This tool is called a cutter Before cutters were invented, each groove had to be individually cut into the barrel VERY labor intensive HIGH possibility of error

Cutters Cutters are usually made of tungsten carbide
Write all Cutters Cutters are usually made of tungsten carbide Harder than steel (or other barrel material) This process leaves microscopic scratches (striation marks). When the lead of a bullet moves through the barrel, it picks up these striation marks, which allows forensic investigators to identify the weapon.

Write all Milling Milling involves the use of rotating multitoothed cutters moved into the workpiece, allowing for a wide variety of cutting operations. Leaves lots of striation marks

Forensic Ballistics Sources of evidence
Write all Forensic Ballistics Sources of evidence Matching bullet to weapon it was fired from Trace analysis of gun residue (GSR) found on a suspect Tracing shell casings left at a crime scene to a particular firearm

Write bold Internal Ballistics Study of evidence produced inside the firearm when a bullet or round is fired Firearm mechanisms Gun barrel manufacturing techniques Firearm recoil Factors affecting internal gas pressure

Write bold External Ballistics Study of a bullet’s flight after it leaves the muzzle of a firearm Most common examinations Reconstructing bullet trajectories Determining maximum range of a given bullet

Terminal Ballistics Study of effect of a bullet on a target
Write bold Terminal Ballistics Study of effect of a bullet on a target Common examinations Determining distance between firing point and target Establishing whether a particular bullet caused a particular wound Determining caliber and type of bullet that caused damage Identifying entry and exit points of bullet in body or target Examining ricochet possibilities of fired bullets

Write all Wound Ballistics Analysis of nature of a wound caused by a particular bullet Bullets spin as they travel through the air As it slows down, bullets become less stable Can tumble end over end after breaking skin Common in M-16 ammo Causes more damage in the body

Wound Ballistics Cavity
Write all Wound Ballistics Cavity Wound created by bullet hitting (living) target Cavity can be 30 times as wide as the bullet’s path Cavity will partially close after bullet passes

Write all Wound Ballistics Amount of damage from bullet proportional to kinetic energy transferred to body Less damage if bullet retains enough energy to cause exit wound More damage if bullet is lodged in the body Type of ammo makes a difference….

Wound Ballistics Elastic tissue Inelastic tissue Lung tissue Bone
Write all Wound Ballistics Elastic tissue Lung tissue Suffers less damage Inelastic tissue Bone Very dense Bullet more likely to fragment Liver, spleen, kidney Very little give, causes more damage

Bullet Types Jacketed Hollow Point (JHP) Metal core Expands upon entry
Write all Bullet Types Jacketed Hollow Point (JHP) Metal core Expands upon entry Not allowed for military use Are allowed for police use in most jurisdictions

Bullet Types Full Metal Jacket (FMJ) Metal jacket Lead Core
Write all Bullet Types Full Metal Jacket (FMJ) Metal jacket Lead Core Non-expanding Used by US Military in accordance with Geneva Convention

Geneva Convention Geneva Convention Adopted in 1949
Write all Geneva Convention Geneva Convention Adopted in 1949 International Rules of Warfare States that militaries may not use expanding bullets, which increase injuries and suffering compared to non-expanding bullets

Bullet Types Armor Piercing Steel or tungsten alloy
Write all Bullet Types Armor Piercing Steel or tungsten alloy Covered by lead + copper or brass jacket Can penetrate certain body armor AKA “cop killers”

From left Hollow Point .22 FMJ .44 Hollow Point .40

Ballistic Fingerprinting
Write all Ballistic Fingerprinting Involves identification of unique marking on bullets and cartridge casings that have been located at crime scenes

Evidence Collection Lift gun w/ 2 fingers on butt
Write all* Evidence Collection Lift gun w/ 2 fingers on butt Only lift when no one in front of muzzle DO NOT stick a pencil or stick in the barrel! Changes striation mark pattern – no more match  Place paper underneath to collect any falling debris such as hair, fiber, powder, etc

Evidence Collection Preliminary Fingerprint Examination
Write all* Evidence Collection Preliminary Fingerprint Examination Keep powder from getting into barrel! Unload gun before transporting to lab DO NOT PACKAGE IN PLASTIC, package bullets separately

Weapon Identification
Write all Weapon Identification Ways to identify weapons: Cutting can be twisted to the right or left Can have different numbers of lands and grooves Can have different rates of twist How many times the grooves twist inside the barrel

How Firearm Evidence is Left
Write all How Firearm Evidence is Left Firing pin strikes base of bullet (primer), detonating primer This ignites the gunpowder Expansion of gases forces casing against the breech, which resists rearward movement and propels bullet down the barrel

How Firearm Evidence is Left
Write all How Firearm Evidence is Left Bullet picks up tiny imperfections from the bore as it passes through (Striations: from lands and grooves) Imperfections are individual to a specific firearm

Testing Questioned Bullets
Write all Testing Questioned Bullets A gun must be test fired and a side-by-side match of the two bullets made using a comparison microscope. The striation marks caused by each gun barrel are unique and can be used to identify from which gun a bullet was fired.

Write bold Ballistics Testing The guns are fired into a large metal tank, roughly 2’ x 5’ x 8’, filled with water. The water stops the bullet, fired at an angle of 30 degrees into the surface of the water without causing any damage. No markings other than striation marks Take a picture for evidence and comparison! After test-firing, the lid of the tank is removed and the bullet is collected.

Write bold Ballistics Testing The bullet recovered from the tank and the question bullet are put under the two stages of a comparison microscope and rotated until the lands and grooves match. If the lands and grooves do not match, the two bullets were obviously not fired by the same gun.

Ballistics Testing The technician then looks to see if the striation marks on each bullet match. If they do not, the bullet may need to be rotated and compared again. The bullet may need to be rotated as many times as there are lands.

Firing Pin Impressions
Write bold Firing Pin Impressions Left during discharge Pin creates microscopic features in indentation when it strikes the primer on a cartridge

Other Markings Ammunition Stamps
Write all Other Markings Ammunition Stamps Contains information about ammunition stamped onto base of cartridge casing by manufacturer

What if… A criminal destroys part of a weapon?
Write all What if… A criminal destroys part of a weapon? In most states, the central police lab has an inventory of different types of weapons that can be used to reconstruct any missing or broken parts of a gun that must be test-fired.

NIBIN National Integrated Ballistic Identification Network
Write bold NIBIN National Integrated Ballistic Identification Network Developed by the FBI and ATF. Computer database with images of fired bullets and fired cartridge cases from crime scenes and test-fired firearms.

Gunshot Residue (GSR) Evidence
Write all Gunshot Residue (GSR) Evidence Consists of gunpowder and primer residues that are ejected from the gun when the weapon is fired Difficult to remove from body and clothing NOT water soluble! Consist of: Gun powder (charcoal, sulfur, KNO3, nitrocellulose) Primer (Lead, Mercury, Barium, Potassium, Antimony)

Write all Gunshot Residue (GSR) Evidence GSR travels a maximum of 3 to 5 feet from the weapon The closer the victim is to the weapon, the more concentrated the GSR will be on the victim GSR comes from several places in the weapon Will be deposited on hand of shooter, shooter’s clothing

Write all Gunshot Residue (GSR) Evidence Contact Shot Typical with suicides, execution-style murders Weapon in contact with victim GSR can blow through the wound tract Heat from the blast may burn skin; star shaped wound

Write all Gunshot Residue (GSR) Evidence Near Contact Shot Heavy GSR concentration on victim Stripling on victim Small abrasions caused by unburned powder and metal fragments striking the skin

Tests for GSR Paraffin Test
Write all Tests for GSR Paraffin Test Hands of suspected shooter are coated in a layer of paraffin wax When wax cools, casts are removed and tested

Write all Gunshot Residue (GSR) Evidence Tests for GSR Sodium Rhodizonate Tests for lead, barium Modified Greiss Test Tests for nitrites Harrison-Gilroy Test Tests for antimony

Validity of GSR Testing
Write bold Validity of GSR Testing Does not absolutely prove a suspect has fired a weapon during a crime May have been near someone who has fired a weapon (secondary transfer) May have fired a weapon legally, not during a crime Need multiple pieces of evidence Three or more elements from GSR OR combination with fingerprints from weapon with positive ballistics match

Sources http://www.schooltube.com/video/dfaaaa768b2f4246ae75/

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