Types of Firearm <ul><li>Shotguns </li></ul><ul><li>Rifled Weapons </li></ul>
Shotguns <ul><li>- The smooth-bore weapon consists of a metal barrel which has parallel sides “double barreled”. </li></ul><ul><li>They usually fire a large number of small spherical lead shot. </li></ul><ul><li>A shot gun is designed for use up to 30 – 50 m. </li></ul><ul><li>Common sizes 19mm, 11mm. </li></ul><ul><li>Ammunition consists of cartridge (metal base containing a central firing cap supporting plastic or cardboard tube). Inside the cartridge there is a wad of paper & cardboard, with a mass of lead pellets. </li></ul>
Rifled Weapons <ul><li>It differs from the shotgun: </li></ul><ul><li>They fire one projectile at a time. </li></ul><ul><li>There barrel has a spiral groove (bore). </li></ul><ul><li>Most of them have a mechanism for bringing a new round into the breech </li></ul>
Rifled Weapons Examples: -- Automatic Pistol: self-loading weapon, where shells are put into firing position by a gas operated delivery system. -- Revolver: bullets are brought into position via a rotating cylinder -- Rifle: a long barreled sporting or military weapon
Rifled Weapons <ul><li>The ammunition comes in many sizes. </li></ul><ul><li>It’s a closed metal cylinder carrying firing cap & a powder. </li></ul><ul><li>When striking the cap the powder burns rapidly producing huge volume of gas that propels the bullet with velocity varying from hundreds to thousands of meters per second. </li></ul>
Mechanism of Injury <ul><li>As missiles traverse the body it causes injury by transferring some of it’s available energy </li></ul><ul><li>Severity of damage is proportional to amount of kinetic energy & the density of the involved tissue </li></ul><ul><li>KE = ½ M * V^2 </li></ul>
Entrance Wounds <ul><li>Shotguns: </li></ul><ul><li>The mass of shot leaves the weapon initially as a solid mass, which progressively diverges from the weapon. </li></ul><ul><li>Contact Wounds (touching the skin) </li></ul><ul><li>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. </li></ul><ul><li>The hot gases & metal fragments are blasted into the body at the same time as bullet. </li></ul>
Contact Wounds cont. <ul><li>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. </li></ul><ul><li>- “Pink/red” staining of the skin (due to carbon monoxide laden gases producing carboxyhaemoglobin) </li></ul><ul><li>Gun powder blackening of the wound edges & surrounding skin (from soot & unburned propellant gases). </li></ul><ul><li>Circular bruise over the skin due to muzzle impact. </li></ul>
Contact Wounds cont. Summery -Wounds are circular -There may be muzzle mark -There may be a slight local burning to the skin & hair -Redness from CO gases
Contact Wounds cont. Muzzle imprint Burning from the powder
Near Discharge <ul><li>- Within few cm of surface </li></ul><ul><li>Large central defect with ‘stippling’ or ‘tattooing’ ( small, dry, reddish abrasions caused by unburned powder & small metal fragments striking the skin) </li></ul><ul><li>Smoke soiling </li></ul><ul><li>Lack of muzzle mark </li></ul>tattooing Intermediate Range
Intermediate Range <ul><li>Within 20 cm to 1 m. </li></ul><ul><li>Diminishing of the smoke soiling but powder tattooing persist </li></ul><ul><li>Burning will be present </li></ul><ul><li>The rim of the wound is irregular forming what is called ‘rat-hole’. </li></ul>
Long Range (2-3m) <ul><li>Satellite pellet holes will be seen around the central wound, which diminishes in size as the range increases. </li></ul><ul><li>the spread of shot in centimeters equal two to three times the range in meters. </li></ul><ul><li>e.g. if the wound pattern is 20 cm across the discharge was roughly 7 – 10 m so couldn’t be a suicide. </li></ul>
Long Range ( 20 – 30 m) -Abrasion collar -No smoke soiling, burning or powder tattooing. -Tissue displacement. -Rarely fatal.
Differences between shotgun & rifles in entrance wound <ul><li>Rifled weapons: </li></ul><ul><li>- show increased amount of tissue destruction due to the high velocities involved. </li></ul><ul><li>Usually have an entrance and exit wound unless bullet has struck a bony area such as the skull. </li></ul><ul><li>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. </li></ul>
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 Entrance Wound Exit Wound with split flaps
Accident, Suicide, or Murder <ul><li>Suicides must show wounds which range within the arms reach unless some devices is present to reach the trigger. </li></ul><ul><li>Suicides shoot themselves in sites of election which include the mouth, the front of the neck, the forehead, or the front of the chest. </li></ul><ul><li>Discharge into the entrance wound are usually on the side of the dominant hand, but this is not absolute. </li></ul><ul><li>People almost never shot themselves in the eye or abdomen & naturally not in inaccessible sites such as the back. </li></ul><ul><li>Women rarely commit suicide with guns & rarely involved in firearm accidents. </li></ul>
Accident, Suicide, or Murder <ul><li>‘A shot woman is a murdered woman until proved otherwise’. </li></ul><ul><li>Multiple firearm wounds suggest homicide, but this is by no means inevitable. </li></ul><ul><li>It’s unwise to state that a gunshot wound must have been immediately fatal, unless destruction of brain stem or heart or transection of the aorta has occurred. </li></ul><ul><li>There are many instances of gross brain damage, especially in the cerebrum, bring followed by prolonged purposeful activity. </li></ul><ul><li>In suicide weapon must be present, though it may be at a distance from the body. </li></ul>
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.