Presentation on theme: "Chapter 15, Firearms. From left 50 BMG, 300 Win Mag,.308 Winchester, 7.62x39mm, 5.56x45mm NATO,.22LR.22LR."— Presentation transcript:
Chapter 15, Firearms
From left 50 BMG, 300 Win Mag,.308 Winchester, 7.62x39mm, 5.56x45mm NATO,.22LR.22LR
Firearms Demo The rifle is chambered for the.577 Tyrannosaurus Rex. According to reloading data, the 13.6 pound rifle At a velocity approaching 2600 fps for a muzzle energy of over foot-pounds. This energy is comparable to that of the US military's.50 BMG cartridge frequently used as a heavy machinegun and anti-material rifle.
Firearms: DC Sniper case Discussion What Forensic evidence can be obtained from firearms? October 2-October acts of violence –10 killed –3 injured –1 assault on a Michaels craft store window
Firearms: DC Sniper case Forensic evidence obtained October 2-October acts of violence DNA, (Multiple Sources) Casings Projectile Fragments Projectiles Later used to confirm –semiautomatic.223-caliber firearm
Firearms: DC Sniper case John Allen Muhammad, 41 Born John Allen Williams Found guilty, received the death penalty his execution by lethal injection on November 10, John Lee Malco, 17 Life without parole
Firearms: DC Sniper case John Allen Muhammad, 41 Mildred Muhammad, the sniper's second ex- wife and the mother of three of his children, told CNN on Monday that she last saw him in 2001 at a custody hearing and had not sought to visit him in prison. "I had emotionally detached from John when I asked him for a divorce," she told CNN. "And my emotions were severed when he said that you have become my enemy and as my enemy, I will kill you. She has asserted that she was her ex- husband's target, and she blamed the first Gulf War for changing his personality.
Gun Safety Rules 1. ALWAYS keep the gun pointed in a safe direction. 2. ALWAYS keep your finger off the trigger until ready to shoot. 3. A LWAYS keep the gun unloaded until ready to use.
Chapter 15, Firearms
What is Firearm Identification? Firearms Chapter 15 Outline What is Firearm Identification? Three basic Rules of Firerarm Safety What is Ballistics Bullet Comparisons, Types Caliber Anatomy of a bullet Cartridge Cases Firearms Types Anatomy Automated Firearms Search System National Integrated Ballistic Information Network (NIBIN) Gunpowder residue Primer residue Serial Number Restoration
What is Ballistics? Ballistics: is the study of bullets and firearms Firearm: a weapon capable of firing a projectile.
What evidence does Firearms Identification provide?.
What evidence does Firearms Identification provide? Comparison of bullets Identification of varying weapon types Restoration of obliterated serial numbers Detection and characterization of gunpowder residues (garments and wounds) Estimation of muzzle to target distance and angle from target Powder residues of hands
Types of Bullet Primers Rim Fire Center Fire
Comparison of bullets
Parts of a Bullet Animation
50 BMG, 22LR22LR The 50 BMG
Comparison of bullets
How a Centerfire Cartridge is Fired
Types of Bullets 1. Frangible Bullets 2. Non-Expanding Bullets 3. Expanding Bullets History: Solving the black powered 3/5 4/5 Jacketed rounds:
Types of Bullets 1. Armor Piercing 2. Blanks: 3. Blended-Metal: 4. Frangible: 5. Incendiary: 6. Lead: 7. Less Lethal, or Less than Lethal: Rubber bullets, plastic bullets, and beanbags 8. Jacketed Lead: Full metal jacket bullets or Ball bullet Soft points or hollow point bullets Steel bullets 9. Non Toxic: 10. Practice: 11. Solid 12. Tracer:
Frangibles Frangible bullets break up into very small pieces upon impact with the target or the background. The penetration of this type of bullet is limited and the inflicted damage is typically near the surface of the target. They are the safest type of bullet to use in semi-populated areas, as the risk of ricochet is minimized.
Non-Expanding Bullets Non-expanding (FMJ) bullets typically retain their general shape as the bullet penetrates and passes through target. The penetration of this type of bullet is usually much greater than frangible or expanding bullets because the frontal area of a non- expanding bullet does not increase as it penetrates. Since the wound channel is typically much narrower than that of an expanding bullet, the damage caused by a non-expanding bullet is usually much less, and quick kills on deer size game are rare. For this reason non-expanding FMJ bullets are illegal for big game hunting almost everywhere in North America. In round nose form they are favored by some African hunters for use on the largest and toughest game, principally on elephant and rhino, where very deep penetration against heavy hide and bone is required.
Expanding Bullets Expanding or "controlled expansion" bullets are designed to deform or "mushroom" as the bullet penetrates and passes through the target. Expanding bullets are the most complex and difficult type of bullet to design, and also the most useful and numerous type of bullet. Almost all big game hunting bullets are of the expanding type. The penetration of an expanding bullet may be measured in inches or feet, depending (among other things) on the bullet's design, the bullet's sectional density, the expansion medium the bullet hits, and how fast it is traveling when it hits the expansion medium. Expanding bullets are normally used to humanely kill animals greater than approximately 30 pounds in weight by creating significant tissue damage as the bullet passes through the animal. Expanding bullets are generally constructed to (ideally) mushroom to approximately twice their initial diameter as the bullet passes through soft to firm tissue, such as skin, fat, muscle, small bones, and internal organs. The objective is to cause catastrophic damage to vital organs, especially the heart and lungs, so that the animal dies as quickly as possible.
Terminal ballistics testing of hollow-point bullets is generally performed in ballistic gelatin, or some other medium intended to simulate tissue and cause a hollow-point bullet to expand.
Armor Piercing An armor-piercing shell must withstand the shock of punching through armor plating. Shells designed for this purpose have a greatly strengthened case with a specially hardened and shaped nose, and a much smaller bursting charge.
Full metal jacket (or FMJ) is a bullet consisting soft core (usually made of lead) encased in a shell of harder metal, such as gilding metal, cupronickel or less commonly a steel alloy. This shell can extend around all of the bullet, or often just the front and sides with the rear left as exposed lead. (A bullet that is completely enclosed by the shell is termed a total metal jacket round.) The jacket allows for higher muzzle velocities than bare lead without depositing significant amounts of metal in the bore. It also prevents damage to bores from steel or armor- piercing core materials.
Caliber vs. Millimeter bore
Understanding Caliber Caliber is simply a unit of measurement of the diameter of the bullet using inches..45 caliber means.45 inches wide. On the other hand, mm is the metric system measurement. 9mm means 9 millimeters wide. To convert use 1 inch = 25mm. ".38 special" measure " and a 9mm measures.355" instead of.354".
Always match the data
38 Caliber and 44 Caliber
Types of firearms Handguns Black Powder Revolvers Semi/Automatic Rifles Black Powder Bolt Action Semi Automatic Fully Automatic Shotguns
Shotguns Gauge One of the earliest ways to designate the size of the bore of a gun was to figure how many bullets for it could be made from a pound of lead. Since at that time all bullets were roundballs of lead, this made a good standard. In time this designation of 'balls to the pound' became synonymous with gauge, so that what our forefathers called '28 to the pound', we now call '28 gauge'. The British commonly used the term 'bore' for 'gauge', so their '28 bore' is the same as '28 gauge' or '28 balls to the pound'. Knowing that there are 7000 grains in a pound, we can simply divide 7000 by 28 and see that 28 gauge balls weigh 250 grains each. If we measure one of those balls, we see that it is.550 inches in diameter. In modern usage that is the same as '.55 caliber'. The same relationship holds true for any size bore, of course.
Shotguns Gauge / Caliber Weight/gr. Balls/lb
Shotguns vs Rifles The major difference between the two is Barrel rifling. Rifles are, Shotguns are NOT Grooves purposely scribed into the barrel of the rifle to induce spin which increases accuracy
The Barrel rifling
Rifling Terminology: Bore : the interior of the firearm barrel Barrel drilling leaves behind irregular marks Rifling: spiral grooves that are formed in the boring of a barrel, designed to produce projectile spin Produces – grooves – lands
Markings on Casing Lands and Grooves Firing Pin Ejector
Firearm Identification Bullet Comparisons Lands - In a rifled barrel, the raised spiral ribs left between the grooves in the bore. This is the part of the barrel that actually engraves the bullet, imparts the spin to the bullet, and ultimately stabilizes the bullet. Rate Of Twist - In a barrel, the length over which the rifling grooves make one complete twist ( i.e. the length of the bore used to turn the bullet one full revolution ) e.g. 1:10 or one revolution in 10 inches. Differs from caliber to caliber. Bullet weight must be appropriate to the rate of twist or bullets will not stabilize in flight. The heavier the bullet, thus the longer, the faster the twist rate must be.
Lands and Grooves
Firearms Identification, Comparison of bullets Inner striations of gun barrel leave impressions on bullet These striations are individual characteristics The widths of the lands and grooves on a bullet provide a further class characteristic that can be used as a preliminary means to determine if the submitted bullet could have been fired from the submitted firearm.
Comparison scope of lands and grooves match up.
Firearms Identification, Comparison of bullets There are three basic machining processes Rifling can be cut into the inner surface of a barrel using a broach, the rifling can be formed using a hardened steel button, the rifling will be formed through a process called hammer forging. A newer method of rifling barrels, called Electrochemical Rifling, does not involve the normal machining processes of the other techniques.
Firearm Identification Bullet Comparisons Rifling will ensure that the bullet flies true with a point-first attitude.. Methods of manufacturing are Button rifling, Cut rifling Hammer forging.
Firearm identification The first step in a firearm identification is to look at what are called class characteristics. These are characteristics common to a particular group or family of items. In the case of a firearm these would be the caliber –The caliber of the firearms refers to the size of the bullet that is fired. Obviously a bullet that is 0.30" in diameter could not be discharged from a firearm that has an inside barrel diameter of 0.15". The rifling pattern on rifling pattern of the barrel. –the inside of a barrel is often unique to a specific firearm manufacturer. This pattern is the spiral staircase pattern that can be seen when looking down the barrel of a firearm.
Comparison of bullets
How a Centerfire Cartridge is Fired
Technologies for analyzing ballistics and firearms GSR Photography/ light tent Comparison Microscopy Distance determination Water tank Ballistics Gelatin National Integrated Ballistic Information Network (NIMBIS)
What are? Drugfire, Integrated Ballistics Identification System National Integrated Ballistics Information Network (NIBIN)
What are? Similar to Combined DNA Index System (CODIS) Automated Fingerprint Identification System (AFIS) 1988, Drugfire, Federal Bureau of Investigation (FBI) 1990, Integrated Ballistics Identification System (IBIS), Bureau of Alcohol, Tobacco, and Firearms (ATF) National Integrated Ballistics Information Network (NIBIN)
Marks left on Cartridge Case Near Firing Pin
Firing Pin Drag Marks
Virtual Comparison Microscope
Exhibit 1 (cartridge case) could neither be identified nor eliminated as having been fired by Exhibit 2 (firearm). The above conclusion is reached if the cartridge case lacks sufficient action marks to be identified as having been fired by the questioned firearm or the firearm in question fails to produce reproducible individual characteristics on standards.
Exhibit 1 (cartridge case) could neither be identified nor eliminated as having been fired by Exhibit 2 (firearm). All general class characteristics such as caliber and firing pin shape would have to agree. The image below shows a comparison between two cartridge cases that lack any individual characteristics but have a similar general appearance.
This conclusion can sometimes be reached when the submitted cartridge case exhibits very good individual characteristics that are very dissimilar to those produced on standards. However, consideration must be given to the possibility that the firearm in question could have changed significantly. If all dissimilarities can be accounted for, a negative conclusion will be reached. The comparison image below shows two cartridge cases that exhibit noticeably different breech marks and firing pin impressions. Exhibit 1 (cartridge case) was not fired by Exhibit 2 (firearm).
Ejector Marks the extractor pulls the cartridge case out of the firearm's chamber. As the cartridge case is pulled to the rear it will be struck somewhere on an opposing edge by ejector. The ejector is designed to expel the cartridge case from the action of the firearm. The resulting impact of the cartridge case with the ejector will cause another action mark that can be used as a means of identification.
3-D Demo: Bullet Comparison
Bullet Comparison Water TankComparison Microscope
National Integrated Ballistic Information Network (NIMBIS) 1999, ATF established and began administration of the National Integrated Ballistic Information Network (NIBIN). ATF administers automated ballistic imaging technology for NIBIN Partners in the United States that have entered into a formal agreement with ATF to enter ballistic information into NIBIN. Partners use Integrated Ballistic Identification Systems Integrated Ballistic Identification Systems (IBIS) to acquire digital images of the markings made on fired cartridge cases and bullets recovered from a crime scene or a crime gun test fire and then compare those images (in a matter of hours) against earlier NIBIN entries via electronic image comparison. If a high-confidence candidate for a match emerges, firearms examiners compare the original evidence with a microscope to confirm the match or NIBIN hit. NIBIN hit. By searching in an automated environment either locally, regionally, or nationally, NIBIN Partners are able to discover links between crimes more quickly, including links that would never have been identified absent the technology.
How IBIS works 1. The IBIS uses sophisticated electronic and optical technology to digitally compare evidence stored in the database. 2. Initially, IBIS equipment photographs the surface of fired bullets and casings from crime scenes and laboratories. 3. Upon entering a new image into the database, the system searches for correlate the new image against previously stored images. 4. Using filters such as: caliber, date of crime, date of entry rifling specifications,. 5. A forensic examiner then visually compares the matched images on a computer monitor 6. If a possible match is found, the images are compared with actual evidence by an examiner on a microscope for a final determination. 7. Once an identification is confirmed in association with at least two different crimes, a unique identifier is assigned for future reference to that image.
Distance Determination Firearm examiners routinely examine a shooting victim's clothing for bullet holes and other evidence that may allow for a determination of the distance from the muzzle of the firearm to the clothing. Determinations are made as to which holes are bullet entrance holes and which are bullet exit holes.
Distance Determination The area around bullet entry holes can be examined for patterns of gunshot residues. If residue patterns are detected they are then compared with test targets produced by firing the firearm in question at various known distances allowing the examiner to approximate the distance from the object that was shot to the muzzle end of the firearm. When ammunition containing multiple projectiles is used in a shooting, the pellet pattern can be used for determining the distance.
Gunshot Residue - GSR
Concentrated deposit of soot and vaporous lead residues.
Ballistics Gelatin used by the shooting industry to simulate soft body tissue, Ballistic Gelatin provides an alternative to live animal or cadaver testing.
Bullet in body – X-Ray
Entrance Vs. Exit wounds
Bullet Trajectory Using Hole A Mr. Vickers was found dead on the floor of his apartment. It was determined that he was shot on the floor after a struggle from eight feet away. What was the arm height of the assailant. Mr. Vickers was found dead on the floor of his apartment. It was determined that he was shot on the floor after a struggle from eight feet away. What was the arm height of the assailant.
Bullet Trajectory Angle of elevation Angle of elevation
Bullet Trajectory A. 2degrees shooter? A. 2degrees shooter? B. 25, degrees B. 25, degrees C. -45 degrees C. -45 degrees
Chapter 15 Firearms Firearms Bullet Comparisons Cartridge Cases Automated Firearm Search System Gunpowder Residue Serial Numbers Tool Marks, Tool Marks, Other Impressions Other ImpressionsFootprintsDentition Tire marks
Tool Marks What are Tool marks? What evidence can be submitted using tool mark? What objects might tool marks be observed on?
Tool Marks Tool marks are scratches and/or impressions that are left on an object that is softer than the object or tool that caused the marks. Evidence submitted: bolt cutters, screwdrivers, scissors, knives, pliers, Crowbars saws. Objects where tool marks might be observed are: wire, sections of sheet metal, chains, safety-deposit boxes, human bone or cartilage, padlocks, doorknobs, bolts, and a variety of other materials.
How are Tool Marks and Ballistics alike? The barrel (harder object) that leaves markings on the surface of the fired bullet (softer object) is an example of a tool mark. The same principle is applied when the tip of a screwdriver scratches a metal surface; the tip of a pry bar scratches or indents a door jamb; or the cutting edge on the blades of a pair of bolt cutters leaves striations on the cut padlock shackle. The unique and individual imperfections on the tool surfaces that are transferred to the softer surface of the damaged object can be used to make a positive identification. To make a positive identification of the tool that may have been used to cause the striations or indentations.
Examination of Tool Marks Whenever a tool mark is found at the scene of crime the following procedure should be adopted for its collections and examination. 1. Photography: 2. Tracing: 3. Lifting of tool marks: Plastic/rubber Dental casting material Plaster of Paris Metal casting Cellulose acetate dissolved in acetone.
Examination of Tool Marks 1. Photography: Tool marks should be photographed. At least two photographs should be taken, one showing the background with the impression and another a close up of the impression. Scale should always be kept at the same level of the tool marks while taking the photograph. Camera should be kept perpendicular to the surface of the tool marks. More details are obtained by using oblique illumination. 2. Tracing: Tool marks can be traced on a tracing paper. This helps in comparing the class characteristics. 3. Lifting of tool marks: A cast or mould is simply a reverse or negative three- dimensional image of an impression. The following materials are generally used for making a mould of a tool mark.
Examination of Tool Marks Lifting of tool marks: A cast or mould is simply a reverse or negative three-dimensional image of an impression. The following materials are generally used for making a mould of a tool mark. Plastic/rubber: This is a material for lifting fine details of a tool mark. A lump of material is softened by pressing in fingers and then applied on the surface. It is pressed carefully as it is likely to be disturbed by out side pressure. Dental casting material: This also gives fine details of tool marks. Plaster of Paris: This material is used when the impression is of large size. Plaster of Paris is partly hydrated calcium sulphate (CaSO4)2 1/2 H2O. First on the surface of tool marks talcum owder is sprayed. This helps in removing the cast without disturbance. Then solution of plaster of Paris is put on the surface. This is allowed to dry and the cast removed carefully. To increase rigidity of surface details a thin layer of shellac dissolved in alcohol is sprayed on the surface by means of sprayer of the type used for spraying insecticides. The shellac is carefully sprayed from a distance of several feet so that air pressure does not disturb the details. The plaster is then poured in. When the caste has hardened the shellac is peeled off. The talcum powder permits the peeling off the shellac without affecting the cast. Metal casting: The mould of tool mark can also be made by metal casting. The suitable metal for this purpose is known as woods metal. This is a metal of low melting point (71oC), which is suitable for casting tool marks. Its composition by weight is Bismuth 50%, Lead 25%, Tin 12.5% and Cadmium 12.5%. Cellulose acetate: Tool marks from stone, concrete, wood, etc. can be lifted by cellulose acetate dissolved in acetone. A layer of 1/16 inch is made. However the cellulose acetate cast should be photographed, with scale, immediately otherwise the layer is likely to shrink.
Tool Marks A tool mark is considered to be any impression, cut, gouge, or abrasion caused by a tool coming into contact with another object. Most often encountered at burglary scenes that involve forcible entry into a building, but also are encountered in homicide cases where an axe or knife strikes bone. Generally, these marks occur in the form of indented impressions into a softer surface or as abrasion marks caused by the tool cutting or sliding against another object.
Tool Marks Just as firearms possess and leave individual characteristics from their manufacture and use, so do tools such as pry bars, chisels, axes, knives, etc. leave marks that can be used to positively identify the use of a particular tool. Tool marks examinations are a comparative examination, where a tool mark or cast of a tool mark are compared with known tool marks produced in the laboratory by the suspect tools. The known and unknown marks are compared microscopically using a comparison microscope.
Tool Marks Spacing between teeth in gripping or cutting instruments can play a major role in forensic tool mark examinations
Other Impressions Suspect shoe print, tire, garment, Glass, paper, tile Photographed with scale Detection: Pathfinder: electrostatic charge on film(mylar sheet) – Good for barely visible prints off colored surfaces. Bloody? – Enhanced by using bromophenol blue, amido black, hugarian red dye, leocrystal violet or patent blue, etc Casting; dental stone, Test impressions compared to known factory standards
What can we learn from cars? From damage? From tire marks
What 1. Make, 2. Model, 3. Submodel 4. Type 5. Number of doors: 6. Year in : 7. Year out: 8. Wheelbase: 9. Front tire tread stance : 10. Rear tire tread stance 11. Turning diameter: 12. Drive wheels: 13. Size of tire: 14. Section ratio 15. Rim size 16. Speed symbol: 17. Standard mounted tire 18. Fuel type 19. Total length 20. Total width 21. Total height:
Skid mark and speed determination Factors affecting skid marks Quality of tire Friction coefficient of road, (wet, dry texture) % Incline or decline
Skid mark and speed determination Windows Media Player - DSL/Cable connection - High resolution (17.3 mb) Speed (mph) Asphalt f = 0.75 Concrete f = 0.90 Snow f = 0.30 Gravel f = '33'100'60' 4071'59'178'107' 50111'93'278'167' 60160'133'400'240'