Firearms by yaofenji

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									Chapter 15, Firearms
 Chapter 15, Firearms

                                                                         From left

50 BMG, 300 Win Mag, .308 Winchester, 7.62x39mm, 5.56x45mm NATO, .22LR
    Firearms Demo
    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 11000 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
 WhatForensic evidence can
 be obtained from firearms?

 October   2-October 22. 2002
   14 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 22
      14 acts of violence
      DNA, (Multiple Sources)
      Projectile Fragments
      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, 2009.
   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

2.    ALWAYS keep your finger off the
      trigger until ready to shoot.

3.    ALWAYS keep the gun unloaded until
      ready to use.
Chapter 15, Firearms

Firearms Chapter 15 Outline
    What is Firearm Identification?
   Three basic Rules of Firerarm Safety
   What is Ballistics
   Bullet Comparisons,
          Anatomy of a bullet
          Cartridge Cases
     Firearms
     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
The Bullet.
Parts of a Bullet Animation
The 50 BMG

 50 BMG, 22LR
   Comparison of bullets
   How a Centerfire Cartridge is Fired
      Types of Bullets
      1.   Frangible Bullets
      2.   Non-Expanding Bullets
      3.   Expanding Bullets

Solving the black powered


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
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:
   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
       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 .356-.357" and a 9mm measures
  .355" instead of .354".
Always match the data
38 Caliber and 44 Caliber
Types of firearms
   Handguns
       Black Powder
   Rifles
       Black Powder
       Bolt Action
       Semi Automatic
       Fully Automatic
   Shotguns
Firearm Anatomy
       Rifle Anatomy
       1.   Stock
       2.   Action
       3.   Sight
       4.   Magazine
       5.   Trigger Guard
       6.   Barrel
       7.   Muzzle

Shotgun Parts
Semi-auto rifle
Bullets travel far! Always make
   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.
Gauge sizing
    Gauge /     Caliber   Weight/gr.
     8.         835       875
    10 .        776       700
    12 .        730       583
    13 .        710       538
    14 .        693       500
    16 .        663       438
    20 .        615       350
    24 .        579       292
    28 .        550       250
 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
      – grooves
      – lands
Markings on Casing
   Lands and Grooves
       Firing Pin
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
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
     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
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
       – The caliber of the firearms refers to the size of the bullet that is
            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
             Photography/ light tent
            Comparison Microscopy
             Distance determination
                   Water tank
                Ballistics Gelatin
National Integrated Ballistic Information Network
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
Centerfire Extractor
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
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
Exhibit 1 (cartridge case) was not
fired by Exhibit 2 (firearm).
• This conclusion can sometimes be reached
  when the submitted cartridge case exhibits
  very good individual characteristics that are
  very dissimilar to those produced on
• 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.
    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 Tank        Comparison
        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.”
   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
     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
Proper Technique
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.
    Bullet Trajectory
Angle   of elevation
                  Bullet Trajectory

A. 50” @ 2degrees shooter?
B. 25”, 00” @10 degrees
C. 65” @ -45 degrees
Firearms                     Chapter 15
   Bullet Comparisons
   Cartridge Cases
   Automated Firearm Search
   Gunpowder Residue
   Serial Numbers
Other Impressions
   Tire marks
    Tool Marks
 What are Tool marks?
 What evidence can be submitted using tool
 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,

   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
 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
 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
1. Photography:
2. Tracing:
3. Lifting of tool marks:
      Plastic/rubber
      Dental casting material
    Plaster of Paris
    Metal casting
    Cellulose acetate dissolved in acetone.
                               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

2.   Tracing: Tool marks can be traced on a tracing paper. This helps in comparing the class

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
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
     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.
      – 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
Same ????
What can we learn from cars?
 From damage?
   From tire marks
 1. Make,                       10. Rear tire tread stance
 2. Model ,                     11. Turning diameter:
 3. Submodel                    12. Drive wheels:
 4. Type                        13. Size of tire:
 5. Number of doors:            14. Section ratio
 6. Year in :                   15. Rim size
 7. Year out:                   16. Speed symbol:
 8. Wheelbase:                  17. Standard mounted tire
 9. Front tire tread stance :   18. Fuel type
                                 19. Total length
                                 20. Total width
                                 21. Total height:
Skid mark and speed

 Factors affecting skid marks
    Quality of tire
    Friction coefficient of road, (wet, dry texture)
    % Incline or decline
   Skid mark and speed
   Windows Media Player - DSL/Cable connection -
     High resolution (17.3 mb)

Speed    Asphalt     Concrete    Snow         Gravel
(mph)    f = 0.75    f = 0.90    f = 0.30     f = 0.50

  30         40'         33'         100'          60'
  40         71'         59'         178'          107'
  50         111'        93'         278'          167'
  60        160'        133'         400'          240'
Skid mark and speed
Columbine High School Video and Discussion
Casings     Bottle bag Origins
       22            TBD
     9 mm          Different
      38            Same
      44            Same
      45           Different
     357           Different
     M16             TBD
     AK47            TBD
     308             TBD
Tools for analyzing Firearms
50 BMG,   300 Win Mag, .308 Win, 7.62x39mm, 5.56x45mm NATO, .22LR

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