Forensic Medicine Handout 2024 PDF

1. Post traumatic epilepsy 2. Meningitis and brain abscess 3. Permanent disability of varying degrees to death. 4. Cranial nerve damage (anosmia, ocular palsies). 5. Cognitive disabilities: Thinking, reasoning, problem sol...

1. Post traumatic epilepsy 2. Meningitis and brain abscess 3. Permanent disability of varying degrees to death. 4. Cranial nerve damage (anosmia, ocular palsies). 5. Cognitive disabilities: Thinking, reasoning, problem solving, and memory are all cognitive skills. The most common of these impairments is short-term memory loss. 6. Sensory problems :(touch, taste, and smell) 7. Language difficulties: Communication problems are common. 8. Personality changes: depression, anxiety, personality changes, aggression 9. Alzheimer's or Parkinson's disease. Causes of death in head injuries Early causes: 1. Cerebral lacerations. 2. Severe cerebral contusions. 3. Diffuse axonal injury. 4. Cerebral compression with brain herniation. 5. Blood loss (from scalp lacerations). 6. Hypoxic/ischemic injury (following airways obstruction due to aspiration of gastric contents or positional asphyxia). Delayed causes: 1- Septic complication, 2- Epilepsy 3- Dementia. Firearm Injuries (Gunshot Wounds) Definition: These are wounds that are caused by gunshots or firearms Role of the physician in gunshot wound: 1. Diagnose the gunshot wound. 2. Differentiate between entrance and exit wound. 3. Differentiate between contact, near and distant range wounds. 4. Determine the direction of firing. 5. Recovery and documenting any projectile. 6. Provide appropriate medical care in living victims. 7. Determine the manner of wounds infliction or death. 8. Notifying the authority. 9. Write a preliminary wound report. Firearms are classified according to: 40 1. The type of missiles they discharge: bullets or shots (guns/shotguns). 2. The presence or absence of rifling (rifled/ non-rifled). 3. The length of the barrel (short/long guns) Principally a firearm weapon consists of three parts; Barrel, Action and Grip. The barrel has smooth or rifled inner surface. Riflings: Are spiral grooves (depressions) that run spirally on the inner surface of the barrel. Rifling imparts rotational spin to the bullet along its longitudinal axis to maintain stability, velocity and power of penetration of the bullet. Classification of Firearm weapons: I. Rifled Weapons : 1. Short Weapons (Handgun): A firearm designed to be fired from the hand and having a short rifled barrel. A) Revolver (non- automatic): Having a revolving magazine (cylinder) which is rotated manually each time the trigger is released. The empty cartridge case is retained within the cylinder after firing. B) Pistol (Semi-automatic): Having a removable magazine in the grip storing cartridges and having a spring for autoloading. This type of weapons automatically ejects an empty cartridge and loads the next one through the gas energy of the previously fired cartridge. It fires one cartridge with each pull of the trigger. 2. Long weapons: o Semi-automatic: they fire one projectile. o Automatic: they fire as the trigger is held down. Π-Non-Rifled weapons: Sport guns. They are smooth bored weapons fires shots, all are long barreled may be double or single barreled, may be semiautomatic. AMMUNITION (FIREARM- CARTRIDGES) Any part of it may contribute to the wounds of the victim. Principally, a cartridge consists of a cylinder (case) with gun powder (propellant) inside, missile (bullet or shots/slugs) on its top and percussion cap fixed in its base. 1- CASE CARTRIDGE It is the outer shell or covering of the cartridge. Function: 1. Keeps the components together 2. Expands and seals chamber against rearward escape of gases. Shape: (a) Straight ("always" pistol ammunition) (b) Bottleneck ("always" rifle ammunition) Extractor flange: The cartridge base has rim except in semiautomatic and automatic guns where the cartridge base has a groove. 41  -Percussion cap: May be at center (center fire) or at side (rim fire), it contains a small amount of a sensitive substance known as primer. Function: explodes on compression igniting the propellant. Composition: 1. Mercury fulminates to produce the spark, now it is replaced by antimony sulfide, barium nitrate or lead stephenate. 2. Powdered glass for friction. 3. K chlorate (O2 donor). MLI: Elemental trace tests used to determine if person fired a weapon. Empty cartridges of non-rifled weapon (sporting gun): A. Fired cartridge of sporting gun indicated by the presence of needle mark on percussion cap B. Non Fired cartridge of sporting gun indicated by the absence of needle mark on percussion cap Empty cartridge of short automatic rifled weapon: Made of brass, has a groove at its base (automatic) A. It is fired because there is needle mark on percussion cap B. Non-Fired cartridge of sporting gun indicated by the absence of needle mark on percussion cap 2- PROPELLANT (Gun powder): Function: Burns to produce large volumes of gases under pressure. Shape: Sheets of smokeless powder cut into disc, flake or cylinder shapes cortide. THE PROJECTILE (missile): It is the part of the cartridge which exits the muzzle. It may be bullets, shots or others as metals, nails, stones. o BULLETS Projectiles of rifled weapons are bullets. Shots (LEAD PELLETS): They vary in shape and size (spherical, slugs). o WADS: They present in shot guns cartridges and they either: 1.External wad: Made of cardboard.1mm in thickness, travels to up to 3m (penetrates within 1m and cause circular abrasion 1-3m), keeps the contents of the cartridge together and may be absent. 2. Internal wad: made of felt 1cm thick, travels up to 10m (penetrates within 3m and causes circular abrasion 3-10m), acts as piston to the shots. MLI of Wads: 1. Diagnosis of firearm injury. 2. Identification of type of the weapon (shotgun). 3. Differentiate between inlet and exit wounds. 4. Estimate the distance of firing. Sequence of Events When Firing A Weapon: - Flashes of light (muzzle flash) are seen before a sound of explosion is heard. 1. Hot explosive gases: (CO, oxides of nitrogen, CO2 & others). Effect: in near injuries the inlet becomes large lacerated, everted edges, reddening (CO monoxide). 42  2. Flame cause burning of the skin & singeing of hair. 3. Smoke (travels a distance of 15-20 cm in handguns) causes blackening of the entrance (soot). 4. Powder particles: (burnt, partially burnt & unburnt), travel a distance of 50cm, cause tattooing (stippling) of the entrance (characteristic sign of intermediate/close/near range). 5. Projectile: ▪ Bullet: Causes single entrance. In distant range the range of firing is denoted by its power of penetration. ▪ Shots: Come out from the muzzle ▪ MLI of powder marks: o Diagnose firearm injuries. o Differentiate inlet from exit wound. o Estimate distance of firing o Denotes the type of powder used. o Denotes the direction of firing. Characters of Firearm Wounds: 1. Loss of substance: more at entrance. 2. Presence of two wounds; inlet and exit but sometimes exit may not be present (gunshot injuries, bullet retained in the body). 3. Powder marks (burning, blackening &tattooing) at inlet (may be absent) or on clothes. 4. Bone beveling; in flat bones. Inlet or exit wound? a- Inlet wound: Shape: 1. Small rounded with marginal abrasions. 2. Stellate or star-shaped inlet: occurs in contact injury over a bone (skull or sternum). b-Exit wound: Shape: Round, oval, slit like, stellate, or crescent shaped. It may be large (high velocity weapons) or small. Item Inlet Exit Loss of substance More (high E absorption). Less. Size Smaller (due to skin Larger due to bullet retraction) except; tumbling & - Near injuries deformation. -Ricochet bullet -Shotgun wounds -Explosive bullets -Very far range. Regularity Regular except: Irregular. -Near injuries -Ricochet bullet -Wrinkled injury 43  Edges Inverted except: Everted -Near injuries -Fatty areas (vacuum behind bullet) -After putrefaction (escape of putrefactive gases) -Explosive bullets Powder marks Present except: Absent -Presence of cloths -Ricochet bullet Distant range Soiling ring Present Absent Carbon effect Present (CO ) Absent Marginal abrasion Present (long. rotatory Absent except if the & bruise movement of the bullet) skin is supported, (a wall or floor). Singeing of hair Present Absent Muzzle print In contact firing Absent Beveling cone- Internal External shaped Mic exam Embedded powder Absent particles Thermal effect (pallisading and streamline) Determination of Firing Distance: a. Contact wound: Results when the muzzle is held against the body at the time of discharge: Round or central defect with marginal abrasion. The size of the defect is comparable to the size of the muzzle opening or bore of the weapon. Over bony surfaces, the wound is stellate patterns The marginal abrasion may be seared or charred Singeing of hair is at the immediate edge of the wound. Soot and unburnt powder in the wound track. Muzzle print (due to ballooning of the tissue by the gas entry). There may also be red discoloration of the surrounding skin from carbon monoxide. b. Close range (near / intermediate) wounds (< 1m) the muzzle is held away from the skin but close enough that it still produces powder tattooing. But no burning or blackening (>20cm) c. Distant gunshot wounds (> 1m) No detectable powder marks reach the skin or clothing of victim. Gunshot wounds are circular or elliptical in shape. 44  The only marks on the target are those produced by the mechanical action of the bullet in perforating the skin as: - Abraded margin → “Abrasion ring”. - Lubricant on bullet surface wiped off onto the wound edge→ grey contact ring → ‟Bullet wipe.” Direction of firing and position of assailant: Direction of firing can be determined by: 1. Joining the inlet and exit by imaginary line if extended from the side of inlet to meet the ground it will denote the position of the assailant 2. From shape of marginal abrasion: a. Tangential--------- elongated furrow. b.Perpendicular-------- abrasion ring is rounded and uniform. c. Oblique-------------- abrasion ring elliptical in shape i.e. thicker at one side which is the direction of entrance. 3. Position of assailant can be also determined by empty cartridges on the ground at the scene. Thermal Injuries This includes: Heat-Related Illnesses. Burns. Electrical injuries. BURNS Types: 1) Thermal burns: (Most common). 2) Chemical burns 3) Radiation burns 4) Electrical Burns THERMAL BURNS Classification of burn: 1) Dupuytren classification: a) 1st degree: redness or erythema of skin. b) 2nd degree: vesicles or bullae. c) 3rd degree: destruction of superficial layers of skin down to sensory nerves (the most painful). d) 4th degree: destruction of the whole skin. e) 5th degree: destruction of S.C. tissues. f) 6th degree: complete charring of the tissues, i.e. carbonization. 2) Rule of Nines: The area involved is estimated by surgical “Rule of Nines”, which is sufficient for prognostic purposes. A large area involved may be more dangerous to life than a deeper more localized one. N.B. It doesn't apply to infants whose body proportions are different from adults. 45