Firearms Examiner In addition to comparing ammunition components to firearms, firearm examiners: Testing firearms to determine if they function properly. Examine clothing and other items for gunshot residues and/or shot patterns. Determine caliber and manufacturer of ammunition components. Determine the manufacturer of firearms. Firearm examiners finish their involvement of a case by presenting their findings in a court of law.
Firearms evidence submitted to a lab's Firearms Section will typically include: A firearm fired bullets spent cartridge cases spent shot shells Shot live ammunition Clothing anything else that may have come in contact with the bullet or residue.
Bullets become scarred by rifling as they travel down the barrel of a gun bsapp.com
Types of Evidence Evidence Characteristics Individual can be identified with a particular person or a single source Fingerprints Blood DNA Typing Class common to a group of objects or persons 5
Types of Evidence Class vs. Individual Evidence These fibers are class evidence; They came from a garment like this one, but there is no way to determine if they came from this specific garment. The large piece of glass fits exactly to the bottle; it is individual evidence. 6
Types of Evidence Class vs. Individual Evidence, continued Which examples do you think could be individual evidence? 7
COMMON TYPES OF WOUNDS Type of Wound Firearm: Contact (muzzle against body) Close (less than 18 inches) Distant (18 inches or more) Incised Stab Puncture Lacerations Defenses Strangulation: Ligature Manual Characteristics No blackening around entry; star-shaped, often with flaps directed outward Blackening around entry; grains of powder and deposits of powder residue None of the above characteristics appear Cutting wound inflicted with sharp-edged instrument, wound typically narrow at ends and gaping in middle with a great deal of blood As above; manner in which knife is thrust into and pulled out of body can result in wounds of different shapes made with same knife Can be caused by ice picks, leather punches, and screwdrivers; result in small wounds with little or no blood Open, irregularly shaped wounds, caused by clubs, pipes, pistols and other blunt instrument wounds accompanied by bruising or bleeding Commonly found on palms of hands, fingers, forearms Mark encircling neck in a horizontal plane overlying larynx or upper trachea; sometimes broken at back of neck where hand grasped ligature; abrasions and contusions of skin not usually present Abrasions, contusions and fingernail marks on skin
A BULLET PENETRATING THE SKIN When a bullet penetrates the skin: the skin is pressed inward the skin is stretched and perforated the skin then returns to its original position 9-13 (Source: Barry A. J. Fisher, Techniques of Crime Scene Investigation, 1992, reproduced with permission of copyright owner, CRC Press, Boca Raton, Florida)
CONTACT BULLET WOUND Contact shots against an exposed part of the body drive soot, metallic particles and powder into the body These materials may be recovered during the autopsy (Courtesy Santa Ana, California, Police Department) 9-14
INCISED WOUNDS Typically bleed a lot Are inflicted with knives or razors Are narrow at the edges and gaping in the middle 9-15 (Courtesy Federal Bureau of Investigation)
Keyhole wound resulting from a tangential source. External beveling of an entrance site Entrance defect in a distal femur resembling a drill hole "Butterfly" fracture of tibia.
Entrance Wounds 1. Shotguns: - The mass of shot leaves the weapon initially as a solid mass, which progressively diverges from the weapon. Contact Wounds (touching the skin) - When a weapon is fired, the bullet, hot gases from exploding gun powder & metal fragments from the bullet & the gun barrel are propelled out of the muzzle at the same time. - The hot gases & metal fragments are blasted into the body at the same time as bullet.
Contact Wounds cont. - Round or oval central defect with an abrasion collar (where the bullet has abraded the skin surface as it passes through it). The size of the defect is comparable to the size of the muzzle opening or bore of the weapon. - Pink/red staining of the skin (due to carbon monoxide laden gases producing carboxyhaemoglobin) - Gun powder blackening of the wound edges & surrounding skin (from soot & unburned propellant gases). -Circular bruise over the skin due to muzzle impact.
Contact Wounds cont. Muzzle imprint Burning from the powder
-Wounds are circular Contact Wounds cont. Summary -There may be muzzle mark -There may be a slight local burning to the skin & hair -Redness from CO gases
Gunshot wound from Pistol
Gunshot wound from Pistol
Gunshot wound from Pistol
Differences between shotgun & rifles in entrance wound Rifled weapons: - show increased amount of tissue destruction due to the high velocities involved. -Usually have an entrance and exit wound unless bullet has struck a bony area such as the skull. -Estimation of firing range is more difficult than with shotgun weapons, but in general, contact wounds show similar features of powder stippling, blackening, burning, tissue disruption, & carboxyhaemoglobin formation.
Gunshot wound from Rifle
Gunshot wound from Shotgun
- Within few cm of surface Near Discharge -Large central defect with stippling or tattooing ( small, dry, reddish abrasions caused by unburned powder & small metal fragments striking the skin) - Smoke soiling - Lack of muzzle mark tattooing Intermediate Range
Intermediate Range -Within 20 cm to 1 m. - Diminishing of the smoke soiling but powder tattooing persist - Burning will be present - The rim of the wound is irregular forming what is called rat-hole.
Intermediate Range
Long Range (2-3m) -Satellite pellet holes will be seen around the central wound, which diminishes in size as the range increases. - the spread of shot in centimeters equal two to three times the range in meters. e.g. if the wound pattern is 20 cm across the discharge was roughly 7 10 m so couldn t be a suicide.
Long Range ( 20 30 m) -Abrasion collar -No smoke soiling, burning or powder tattooing. -Tissue displacement. -Rarely fatal.
Exit wound -Shotguns: Rarely produce exit wound because they traverse the body, but if happened it may cause a huge ragged aperture wound. -Rifled weapons: --Exit wound is usually everted with split flaps. --No burning, smoke or powder soiling. --if the bullet flattened or has destruct some bone internally, exit wound may be more irregular and sometimes very large in size.
Exit wound Exit Wound with split flaps Entrance Wound
Doctors duty in firearm injuries & deaths -Any missile, foreign body such as wads and any skin removed from the margin of a repaired firearm wound should be carefully preserved for the police. -The skin in post-mortem examination around the entrance wound should be removed & kept without formalin, but refrigerated if necessary, for forensic tests for powder residue. -In many countries firearm injuries must be reported to the police even if not fatal.