Final - Shooting Reconstruction

Bullet Defect (Glass)

*Plate* (store front) → flat, clear, smooth surface, lacking any treatments of construction *Tempered* (side window of car) → stress built in during manufacture to prevent sharp edges from occurring upon breakage (side and rear car windows) *Laminated* (windshield)→ two sheets of plate glass cemented around a piece of plastic/laminate (Exit side of glass is always wider then entry side of glass) *Fractures* -Concentric - circular -Radial - running off -2nd bullets fracture lines do not cross/pass 1st bullets fracture lines

Six Physical Findings of Entrance Wounds

1. Bullet → Abrasion Collar 2. Burned Gunpowder → Soot 3. Flame → Seared Skin 4. Injected Gas → Triangular Tears 5. Muzzle → Muzzle Contusion, from injected gases expanding skin against the gun barrel 6. Unburned Gunpowder → Tattooing/Stippling (dots that cant be wiped off)

Four parts of the Cartridge

1. Cartridge case → container for all other components of the cartridge, exclusive of the bullet/projectile 2. Primer → this compound explodes when struck by the firing pin and ignites the powder 3. Powder charge → the gun powder 4. Bullet/projectile → the projectile portion of a cartridge that emerges from the barrel and travels towards the target --Core - portion of bullet underneath the jacket --Jacket - metallic covering over the core

Intermediate Range

5 to forty inches -tattooing -abrasion collar -no soot

Rifled Barrel

Barrel of gun can be rifled to put spin on bullet; increase accuracy Inside of barrel has hills (lands) and valleys (grooves) Lands and grooves twist down length of gun

Cartridge Case Individual Characteristics

Breech face marks Firing pin impressions Chamber marks Extractor marks Ejector marks

Class Characteristics of Bullets

Caliber (size) # Of lands/grooves Direction of rifling twist Degree of twist Width of lands/grooves

Class Characteristics of Cartridges

Caliber (size) Firing pin location Firing pin size/shape Extractor/ejector sizes Relative location of extractor/ejector

Types of Contacts/Ranges

Close contact → pressed to the skin Loose contact → close proximity to the skin, small gap Close → not more than five inches from the wound Intermediate Range → 5- 40 inches from the wound Indeterminate Range → no characteristics, so no conclusion

_____________ _______________ is used to compare striations on bullets

Comparison Microscope *Striations* = tiny scratches on bullet that can be specific to a single gun

Bullet Defect (French Fry)

Compressed and punched out section of foam padding creating the shape and appearance of a French fry

Internal Ballistics

Conducted by the Forensic Firearms Examiner at the crime lab Involves function and operation of the weapon, and association of weapon to bullets and casings (comparing "test fire" → test fires into water tank) Often involves evaluations of gun shot residue range determinations

Terminal Ballistics

Conducted by the Forensic Pathologist, FFE, and CSI Involves defining the path of a bullet through the body, the associated damage and differentiating entry from exit wounds Also incudes issues of range determinations The study of the behavior and effects of a projective when it hits its target

Defects

Damage produced on a target as a result of projectile impact 1. Perforation Defect --> going though something 2. Penetration Defect --> going into something

Bullet Defect (Entry)

Defects in a variety of surfaces Generally have a circular or elliptical aspect

Terminus

Final resting place where projective ends up after its flight path

Range Determinations

Forensic firearms examiners use the weapon and similar ammunition to create gunpowder residue standards at different distances. These are then compared to the questioned residue

Inside of a barrel has __________________ and ____________________

HILLS (lands) and VALLEYS (grooves) Twist down length of gun (lands and grooves)

Smooth Barrel

Hollow tube

Bullets

Intact Bullet → projectile in one piece Fragment Bullet → bullet, jacket or metal frag Deformed Bullet → indicates projectile damaged from its travel

Internal ballistics: up to a point, the _______________ the barrel, the ________________ the acceleration

Longer; Greater Velocity is the primary factor that causes impact

Cartridge Case Class Evidence

Manufacturer, Shape, Caliber, Composition

NIBIN

National Integrated Ballistics Information Network Specialized computer network in US --> national databases containing images of recovered images of ballistic evidence

Bullet Defect (Exit)

Not symmetrical

Trajectory Kits

Primary concern of external ballistics is evaluating bullet defects Trajectory kits are used to this, they include: -Trajectory rods -Centering guides -Angle finders -In some cases, lasers

Embedded

Projective stuck in or protruding form a target surface

Cartridge

Single complete round of ammunition

Exit Wounds

Size of wounds does not differentiate entrance from exit wounds *Configuration of wound does!* -irregular borders -lacks soot/lacks tattooing -no abrasion collar (except in a shored exit - pressed against wall)

Manufacturing of Rifled Barrel

Starts with hollow tool and machine makes grooves and lands though tube Minor differences in manufacturing leads to differences in the scratches (striations) on fired bullet

If class characteristics and striations MATCH:

The bullet was likely fired by the suspect gun

Flight Path

The path of a projectile in flight (flight path rods illustrate this)

If class characteristics MATCH but the striations DO NOT:

The results are inconclusive

If class characteristics and striations DO NOT MATCH:

The suspect gun can be excluded

External Ballistics

The unpowered free-flight phase of the bullet after it exists the barrel and before it hits the target Conducted by the crime scene analyst most often, may involve the firearms examiner Involves defining the path of a bullet through the scene by evaluating various scene aspects, such as penetrations and perforations, casings and known positions of the victim or shooter Ultimately it defines possible and impossible scenarios for bullet trajectories

Concerns: Tumbling vs. Deflection

Tumbling -Tumbling through something else -Tumbling bullets often create distinct characteristics -Obvious tumbling eliminates any ability to evaluate impact angle Deflection -Bullets that deflect create distinct defects -The bullet itself may show indications of the angle at which it deflected

Angle of Incidence (Angle of Impact)

Use acute angle, must use a direction (left/right, front/back). A complete descriptions requires a measurement to both the vertical and horizontal plane Two components: 1. Angle Degree Component 2. Directionality Component

The cause and effects produced as a result of a bullet impacting a target surface:

Velocity of the bullet Bullet design Mass of the bullet KE energy remaining on impact Resistance of the target Deformation of the bullet Amount of KE lost to the target surface

Increases in bullet __________________ have greater effect on kinetic energy than increases in bullet ________________

Velocity; Mass As a bullet exits a barrel, it posses kinetic energy

Utilizing a Trajectory Kit

Visual examination Presence of bullets or remnants Chemical presence of lead or copper Insert the rod into perforating defect Use centering guides to level the rod (centering guides can affect the angle)

Close Range

Zero to five inches -soot -abrasion collar -may have stippling