Forensic Medicine Handout 2024-26-34 PDF

The total chance of exclusion using ABO system combined with all the other systems is 93%. Thus, the more systems tested the more likely a wrongly accused father is to be positively excluded from paternity. Such blood grouping can exclude a man being the father but c...

The total chance of exclusion using ABO system combined with all the other systems is 93%. Thus, the more systems tested the more likely a wrongly accused father is to be positively excluded from paternity. Such blood grouping can exclude a man being the father but can never totally confirm his paternity. Power of exclusion using DNA in paternity test is 99.9%. Medicolegal Aspects of Wounds Wounds: Definition; is a "disruption of the continuity of tissues produced by external mechanical force". Wounds classification Legal classification: 1. Minor wounds: heal in less than 20 days leave no permanent infirmity. 2. Dangerous wounds: take more than 20 days for healing and or causing permanent infirmity. 3. Fatal wound that cause death of the victim. Medical classification of wounds: 1. Abrasions (or grazes or scratches). 2. Bruises (or contusions or ecchymoses). 3. Lacerations (contused). 4. Incised wounds (cut). 5. Puncture (or stab) wounds. 6. Gunshot wounds (GSW). Abrasions 'Graze' or 'Scratch' Definition: It is damage to the superficial layer of the skin (epidermis), therefore causes no bleeding. However, abrasions do usually extend into the dermis causing slight bleeding. Causative force: blunt force Medico legal importance: A. Shape: Takes the shape of the causal object: 1. Finger nails abrasion 2. Ligature mark 3. Bite marks 4. Patterned abrasion B. Site of abrasion: It reflects the site of impact (around the neck in throttling) & the sort of the assault (at the inner aspect of the thigh denote rape). C. The direction of injury and position of the assailant : D. Age of abrasion can be compared with date of the assault: First 2 days: soft scab. After 3days: dry scab. 26  After 1week: falling of the scab leaving red area. After 3 weeks: disappears leaving no scar. E. Post- mortem abrasion: is brown and leathery, while ante-mortem abrasion usually associated with bruise & microscopic examination reveals cellular infiltration. Bruises / Contusions Definition: it is 'extravasations' of blood into surrounding tissues from damaged capillaries or venules. Causative force: blunt trauma such as: 1. A blow or a fall. 2. Squeezing or pinching. Medico legal importance of bruise: A) Shape of bruise may denote the causal instrument B) Site of Bruise: Usually denotes site of blow, but sometimes shift from its original site. C) Age of the bruise: Denoted by color changes due to the degradation of hemoglobin in blood which from the periphery towards the center. Most bruises disappear within 1-4 weeks of infliction; this time frame is extremely variable depending upon the size and depth of the bruise, its location and the general health of the individual. The color changes are: o Red (fresh): oxyhemoglobin. o Blue: reduced hemoglobin. o Green (after 4-5 days or later): biliverdin. o Yellow (after 7-10 days or later): bilirubin. D) The size (extent) of a bruise: Size of bruise depends on several factors: a- Type of tissues: Lax tissues e.g. eyelids and genitals bruise easily than fibrous tissue. e.g. palms, soles and scalp. b- Age: Infants and the elderly tend to bruise more easily than young and middle-aged adults. The former because of the looseness and delicacy of the skin, and the abundant subcutaneous fat; the latter because of degenerative changes in the tissues which support the small blood vessels of the skin and subcutaneous tissues. c- Sex: Women bruise more easily than men because they have more subcutaneous fat, and this is particularly true of obese women. d- Natural Disease: e- Skin color: f-Rapidity of death: N.B. Deep bruises may require as long as 12 or 24 hours to become apparent and some may never do so. 27  E) Ante Mortem or Postmortem: Postmortem bruise can occur due to blunt force impact→ rupture blood vessel→ extravasation of fluid blood into the surrounding tissues. PM bruise is small produced in areas of hypostasis, or where tissues can be forcibly compressed against bone, e.g. over the occiput. Lacerated Wounds (Contused Wounds, Tears, Splits) It is splitting of the skin by direct crushing of blunt trauma. e.g. motor vehicles accidents fall from heights, heavy sticks. Wound description: 1. Ragged or lacerated edges. 2. Abrasion and bruising at edges. 3. Crushed blood vessels. 4. Hairs driven into the tissues and crushed edge. 5. Tissue strands (nerves, fibrous strands, vessels) may cross the depths of the wound. 6. Relatively little blood loss (except scalp). 7. More liable for infection. 8. Heals usually by secondary intention. MLI of lacerations: 1. Shape and size not usually related to causal object. 2. Trace evidence in wound (Foreign Body). 3. Rarely self-inflicted. Incised Wounds (Cuts) Definition It is destruction of the full thickness of the skin due to contact with a sharp edge e.g. knife, razor, and broken glass. Classic example: cut throat, cut wrist. Wound description: 1. Edges are regular and cleanly cut, except if the weapon edge is not sharp enough. 2. More long than deep. 3. Hair edges are sharply cut. 4. Bleeds profusely. 5. Reflects sharp edge not weapon type. 6. Direction of cut: deeper at the start. 7. No abrasions or bruise at edges. 8. Heal usually by primary intention. MLI of incised wound: 1. Reflect sharp edge, not weapon type. 2. No trace evidences. 3. Profuse external hemorrhage and air embolism. 28  4. Danger to life depends on site and depth. 5. Incised wounds may be self-inflicted, assault or accident. Age of incised wounds: – Age of incised wounds may be compared with the date of a certain crime. – First 12 hours: The edges are red and swollen. – By the end of 36 hours: New vessels start to grow towards the skin surface. – After 5 days: New vessels start obliteration. – After 10 days: The wound is healed by primary intention. – After 3 weeks: The scar is red. – After 3 months: The scar is coppery brown. – After 6 months: The scar is white and may be invisible. To detect it, we rub the skin to cause hyperemia; the scar is pale being avascular. Stab Wounds They are penetrating injuries whose depth within the body is much greater than length. Causal instrument: Sharp pointed object e.g. knife or dagger. Non-sharp pointed object: needle, pin (punctured wound). Wound description: 1. Depth is much greater than the dimensions of the wound on the body surface. 2. Elliptical in shape. 3. Clean cut edges with gaping. 4. No bruising or abrasion of margins. MLI of stab wounds: 1. Shape of Wound May indicate: Cross-sectional shape of knife blade e.g. - Double-edged blade → Slit with two sharp ends. - Thin, single edge blade → Triangular slit, one sharp end. 2. Wound Length may indicate blade width 3. Wound Track Depth may indicate length of weapon 4- Broken tip of weapon can be found in wound. Fabricated or Self-Inflicted Wounds These are simple wounds which are self inflicted (or fabricated) by the person on his body. Characters of Fabricated Wounds: 1. Superficial and relatively harmless. 2. In an area readily accessible to the victim and in a safe site e.g. extremities, forehead, etc…. 3. They are inflicted on bare skin, so no corresponding tear on clothes. 4. The age of the wound does not usually correlate with the date stated by the fabricator. 5. Careful examination and interrogation about the manner of assault or type of weapon will prove that allegation was false, e.g. firearm wound: punctured by a nail and burned with a cigarette. 29 Defense Injuries These are injuries sustained by the victim to defend himself. 1. In case of punching, kicking: 2. In attacks by knife: 3. In kicking: Complications& Causes of Death from Wounds I. Shock: Types: 1. Neurogenic shock: failure of the nervous system to control the diameter of blood vessels. Causes: Trauma to a trigger zone(epigastrium, pericordium,testicles). Spinal cord injury at or above T5. Spinal anesthesia. Severe pain. 2. Hypovolemic shock: loss of blood and other body fluids. 3. Cardiogenic shock: failure of the heart to pump blood adequately to all vital parts of the body. Causes: Myocardial contusion. Arrhythmias. Obstructive disorders: tension pneumothorax, pericardial tamponade. 4. Septic shock: Due to presence of severe infection. 5. Anaphylactic shock: Caused by a life-threatening reaction of the body to a substance to which a patient is extremely allergic. 6. Traumatic shock: As tissue destruction leads to the release of inflammatory mediators leading to disruption of the micro vascular endothelium (Systemic Inflammatory Response Syndrome SIRS). Causes: Crush injuries, major fractures, and major burns. Ischemic/necrotic tissue: pancreatitis, myocardial infarction. Clinical picture of Shock Sinus tachycardia: >90 beats/min, except in neurogenic shock. Respiratory rate >29 breaths/min. Decreased Urine Output: 3 consecutive ribs on both points→ flail chest (paradoxical chest movement), pneumothorax & or hemothorax, pulmonary contusion& laceration. o Injury to liver (fracture ribs 7-10 on right side), spleen (9-10 left side) & kidney (11-12). C) Abdominal injuries: Abdominal skin injury: Is rarely seen, particularly if impact is over a broad area. Liver, spleen, kidneys, intestines: are vulnerable to compression and laceration against the spine following the blunt impact of road traffic accident (RTA) or assault. Site of election for stab wounds with penetration of vascular organs such as liver, spleen, kidney, mesentery or major vessels such as aorta, vena cava with severe blood loss into the peritoneal cavity. Peritonitis may follow intestinal damage. HEAD INJURIES Definition: It is any damage to the scalp, skull, meninges and the brain due to mechanical trauma. Types of mechanical trauma& mechanism of head injury: ❖ Blunt trauma: either: 1) Direct impact trauma 2) Inertial trauma is caused by: A. Rapid rotational acceleration or deceleration of the head. B. Linear acceleration/deceleration (Whiplash). ❖ Penetrating trauma by an object e.g. knife or other penetrating object or missile (GSW) damage occurs along the route the object has traveled in the brain. Scalp Injuries Scalp hematomas: either 34