Presentation on theme: "By Dr. Abeer Abdel-Wahab Sharaf Eldin Assistant professor of Forensic Medicine and Clinical Toxicology Forensic Medicine and Clinical Toxicology."— Presentation transcript:
By Dr. Abeer Abdel-Wahab Sharaf Eldin Assistant professor of Forensic Medicine and Clinical Toxicology Forensic Medicine and Clinical Toxicology
General Firearm terminology A firearm : it is a weapon that uses the force of an explosives propellant ( powder) to project a missile المقذوف. Action الجزء الفعال : The part of firearm that loads, fires and ejects a cartridge. Barrel الماسورة : The metal tube through which the missile is fired. Bore: The inside of the barrel. Breech القاعدة : The end of the barrel attached to the action. Muzzle فوهة : The end of the barrel out of which missile come. Rifling الخشخنة : The spiral grooves cut inside a gun barrel that give the bullet a spinning motion. The metal between the grooves is called a land.
Types of Firearms
Rifled weapons The bore containing rifling. They fire a single missile at a time called bullet. They have short or long barrels. Caliber: the diameter of the bore ( inside of the barrel) measured from land to land.
Functions of rifling ? Functions of rifling ? A- The Rifling giving the bullet its spiraling, spinning motion increasing range of firing, power of penetration and decreasing Resistance ( air or gravity). B- It gives the bullet stability increasing Range of firing and power of penetration Lands Grooves
Smooth-bore or non-rifled weapon The bore is smooth and contains no rifling. They fire a large number of small spherical lead balls. They have a long barrel. The caliber of a shotgun: it is expressed as its gauge, which is the number of equal lead balls, each of which exactly fits the inside of the barrel of the shotgun, that equals one pound. The bigger the caliber, the smaller the diameter of the bore.
Sporting gun Or Sporting gun Sporting gun Or Sporting gun
Ammunition of rifled weapon It is the nature of propellant charge ( gun powder ) and the projectile. 1-Cartdridge الخرطوش 2-Projectiles (missiles المقذوف ). Bullets. 3-Gun powder (Propellant charge). Black powder. Smokeless powder.
Cartridge The basic unite of ammunition, also called round, made up of : cartridge case, primer, powder and a projectile. It is a closed metal cylinder carrying the primer in its base and propellant charge, a single projectile is clamped into its distal end. It is usually made of brass. The caliber and the name of manufacture are stamped on its base. Hand guns cartridge are short and have straight design, while rifle cartridge are long and bottle- necked.
Primer It is small tube located either in the rim (rim fire) or in the center of the base(centre fire) of the cartridge. The primer composition is formed of 3 substances: mercury fulminate, k chlorate and powdered glass. MLI: 1- Start the process of firing. 2-Primer tell whether the cartridge was fired or non- fired. 3-Identification of the weapons.
Propellant = Powder
Smokeless powder The powder used in the cartridge case is smokeless powder. It is consists of a nitrocellulose ± nitroglycerin. It may be : flake, ball, cylindrical. After ignition, it leaves a little neutral residue, so it is really not smokeless. One volume of powder produce 900 volume of gases.
Black powder The old form of gun powder and consists of : 75% nitrates, 15% carbon and 10% sulfur. It is a black irregular small granules. After ignition, it leaves a heavy alkaline residue. One volume of powder produce 300 volume of gases. It is no longer used in modern weapons.
Missile المقــــــــــــــــــــــــــــــــــــــــذوف Called bullet. It may be jacketed or non-jacketed. Handgun bullet is short with round tip while rifle is long with pointed end. Bullets may be: 1-Explosive bullets: dumdumised or devastator 2- Rubber or plastic bullets.
Ammunition of non-rifled firearm Cartridge: consists of a metal base containing a central percussion cap, supporting a cardboard or plastic cylinder. Inside the lower part of this cylinder is the gun powder covered by internal wad, which separates the gun powder from the lead shots. The open end of the cartridge may be closed by external wad or crimped to keep the shots in place. Missiles : are wads and shots. Gun powder either black or smokeless.
Whenever a gun is fired, the following emerges from the muzzle of the barrel in a conical cloud
Missiles: bullet or wads and shots. A jet of flame: 1-2 inch in length, 1400 F. A cloud of gas. A residue: A- Powder residue: * Unburned particles of gun powder. * Partially unburned particles of gun powder. *Carbon or soot from burnet gun powder. * nitrates and nitrites from burnet gun powder. B- vaporized metal from the primer, cartridge case and bullet or its jacket.
Ballistics This term refers to the science of the travel of a projectile in flight. The flight path of a projectile include: 1- Internal ballistics: it is travel of a projectile down the barrel. 2- External ballistics: it is the path of a projectile through the air from gun to the target. 3-Terminal ballistics: it is the path of a projectile through a target.
The doctor duty in firearm injuries and deaths In the living Saving life. Recording the general appearance before any surgical cleaning or operative procedures. Preserving any missiles without damage and any skin removed from the margin of a repaired wound as well as clothing for police to be analyzed. Firearm wounds must be reported to the police even if not fatal.
In the dead Is the injury a gunshot wound? What is the range of fire? What is the direction of fire and the position of assailant in relation to the victim? Is this gunshot wound belonging to a certain type of firearms, and is it one or more? Is death caused by this gunshot wound? What is the manner of death?
Is the injury a gunshot wound?
Gunshot wounds are either: 1- Perforating wounds: occur when missile passes completely through the objects, causing an inlet and exit. 2- Penetrating wounds: occur when a missile enters an objects and doesn’t exit ( inlet only). 3-Both penetrating and perforating : occur when a missile strikes the head and passes through the skull and brain and rests under the scalp, thus producing a penetrating wound of the head, but perforating wound of the skull and brain.
Thus, gunshot wound should be d.d. from wounds caused by blunt objects with pointed end. Loss of substance. Presence of two wounds, inlet and exit. Powder marks Beveling of flat bone. Soiling ring (grey ring). Abrasion ring (collar)
Beveling of bone The bullet displaces the fragments of bone in the direction it travels. In the skull; the entrance shows a small rounded hole, in the outer table, larger in the inner table i.e. internal beveling. On exit from the cranium it causes smaller defect in the inner table and larger in the outer table i.e. external beveling. Beveling occurs also in sternum, iliac crest, scapula and ribs.
Beveling of flat bone
What is the range of firing? Wounds from rifled weapons
Near-contact shot The muzzle is held at a range of 1-2 inches(2.5-5 cm )for rifle or less than 10 mm with handgun. Circular or oval inlet depending on the direction of fire with inverted edge. Ring of blackened and burnt skin and hair around the inlet, which is wider than one seen in a loose contact shot. Dense tattooing around the inlet.
Intermediate range shot (close- range) For handgun -----30-45 cm For rifle ------90-120. Circular or oval inlet depending on direction of fire. Some blackening and burning of the skin and hair around the inlet. Less dense tattooing around the inlet.
Distant shot Distance beyond one meter or more Circular to oval inlet. No blackening, burning or tattooing. Abrasion ring and contusion ring around the inlet edge. Gray ring overlay the abrasion ring.
Wounds from smooth-bore guns The shot leaves the muzzle in a compact mass within the wad, but as the distance increases, the wad falls back and the bolus of shot begins to diverge so that the shot pattern is a long shallow cone.
Contact shot Circular inlet about the size of muzzle with regular edge over soft areas and satellite over bony areas. Blackening and burning of skin around the inlet in loose contact but not in hard contact. A cherry red color of the soft tissue. Muzzle mark. Wads inside the wound. No shot marks.
Near-contact shot Up to 5 cm of the body surface, this will be similar contact shot. No muzzle marks. Marked blackening and burning of the skin and hair around the inlet. Dense tattooing around the inlet.
Intermediate range This range is up to one meter. Diminishing blackening and burning. Less dense tattooing. Spread of shots, this begin at about one meter, first causing an irregular rim to the inlet which is called the rat-hole.
Distant shot No blackening, burning or tattooing beyond 120 cm to 2 meters. The wads fall at distance from meters (external wad) to 7 meters ( internal wad). The shot will spread progressively: at 2-3 meter ---> central inlet surrounded by satellite shot holes, the central inlet diminish in size as the range increase. at 4 meters-- > shot dispersion without central wound. At 20-30 meters--- > there is uniform peppering of shots.
To prove or disprove statements of the accused. To rule in or out the possibility of suicide. To help establish the nature of the accident.
What is the direction of fire????
Identification of inlet and exit. Appearance of the inlet wounds. Trajectory between inlet and exit: the course of the bullet through the body can be determined by x-ray of the cadaver or autopsy. The site of cartridge case at the crime scene: this may determine the position of the assailant.
Identification of inlet& exit
Inlet & exit
Appearance of inlet
Exit wounds in non-rifled weapons: It is uncommon to have exit Except If pellets strike the body at acute angle and bones in the way At near firing.
Is this gunshot wound belonging to a certain type of firearm???
The type of firearm can be identified from: A- nature of the inlet wound. B- type of missile extracted. C- type of cartridge case. D-Marks on the cartridge case. E-Marks on the bullet.
Marks on the bullet When the bullet is fired down the barrel, the rifling imparts 2 types of markings to the bullet. Class characteristics: these are rifling marks and can identify the make and model of the weapon. Individual chacteristics: these are marks made by imperfection in the barrel. No two firearms share in these characteristics even if they were from the same factory ( Confirmatory marks). These marks should be compared by comparison microscope with a test bullet from the suspected weapon.
The rifling marks differs from a weapon to another according to: Number of lands and grooves Width of the lands and grooves Direction of twist Depth of the grooves Rifling is considered as a family characteristic (class) for each weapon Left Right 12 3
As the bullet passes through the barrel rifling bites on the bullet giving it the same class characteristic so it can identify the weapon and they are called Primary rifle mark 12 3
Shooting in a Water Tank
Striation Comparison under a microscope
Marks on the cartridge case Firing pin markings on the primer. Breech block markings on the cartridge base (confirmatory marks). Ejector markings around the edge of the cartridge. Extractor markings on the rim. Magazine markings on the side. These marks should be compared by comparison microscope with a test cartridge case fired from he suspected weapon.
Is death caused by this gunshot wound????
Autopsy and microscopic examination can determine the cause of death, and whether the wound is ante and postmortem
What is the manner of death??
The opinion about whether death is suicide, homicide, or accidental can be established from: A- Circumstantial evidence. B- Examination of the crime scene. C- Postmortem examination of the victim. D- Examination of suspected person, i.e. the shooter E- Examination of the weapon
X-ray in fire arm injury Why is it important ? To locate and identify the bullet, pellets, jacket or fragments. To delineate the track to outline the direction of fire. To determine defects in bone. To provide document for injuries present. To rule out the presence of a missile.