Forensic Science: Wounds and Injuries Quiz

Wounds & Injuries

• Wounds & injuries are disruptions to normal tissue structure caused by force.
• Distinguishing wound types is crucial for assessment.
• Learning outcomes include describing different injury types and why they're distinguished, factors assessed in sharp force trauma, features of gunshot wounds, and vehicular impact injuries.
• Accurate documentation is vital in forensic/non-forensic autopsies, identifying the weapon used (e.g., blunt or sharp object), assessing injury patterns for accident/suicide/homicide, and accurate medicolegal reporting.
• Injuries must be described with specific details: wound type (bruise, abrasion, laceration), dimensions (length, width, depth), and photographs with a scale.
• Stab wounds require measurements of the wound's appearance, with edges drawn together later.
• Position of the wound relative to anatomical landmarks is important (e.g., midline, clavicle, ear lobe).
• Height of wound from ground level is crucial for documentation.
• Different injury types exist: Blunt force trauma, Sharp force trauma, and Mixed injuries (combinations).
• Blunt force trauma includes bruises, abrasions, and lacerations.
• Sharp force trauma includes stab wounds and incised wounds.

Types of Injuries

• Blunt force trauma: Impacts resulting in tissue damage without breaking the skin.
• Abrasions: Scrapes or grazes of the skin.
• Bruises: Discoloration due to blood vessels.
• Lacerations: Tears in the skin.
• Sharp force trauma: Incised wounds: Cuts/tears. Stab wounds: Penetration.
• Wound descriptions should consider edges (clean cut versus ragged), the presence of embedded foreign materials like dirt, and direction of the force.

Medical Evaluation of Bruises

• Evaluation focuses on location, number, distribution, color, size, shape, and patterns (grip, finger marks)

Tramline Bruise

• Two parallel linear bruises separated by paler, undamaged skin.
• Occurs when skin is struck by a rod-shaped object, with blood leaking into surrounding tissues due to stretched and torn blood vessels.

Abrasions

• Known as scratches or grazes.
• Direct or glancing impact, causing epidermal loss only.
• Often broader (“brush abrasion”) e.g., from a fall, motorcyclist skid.
• Retains surface characteristics from the object that caused it.
• Direction of force can be inferred.

Forensic Significance of Abrasions

• Abrasions retain surface characteristics of the impacting object (e.g., car bumper).
• Force direction can be determined from the torn epidermis.
• Heaped-up strands and ragged edges towards the force direction.
• Embedded materials are indicators.

Lacerations

• Cuts, tears, or splits in skin and underlying tissues.
• Often associated with blunt force trauma.
• Common in areas with underlying bony support.
• Characterized by ragged edges, crushing, and bruising at the margins.
• Hairs in the tissues are a marker.
• Tissue strands crossing through deep wounds, including nerves, fibrous bands, and vessels.
• Can be mistaken for incised wounds when caused by a regular shaped object (e.g.., scalp lacerations).

Sharp Force Trauma

• Caused by sharp instruments, producing neat cuts and tears.
• Incised wounds are usually longer than deep; wound margins are uninjured.
• Stab wounds are deeper than they are wide; characterized by entry and exit wounds.

Stab Wounds

• Depth is significantly greater than the length.
• Often due to knives, bayonets, swords.
• External surfaces have slit-like appearances; skin contracts when object is removed.
• Centre of the wound widens.
• Size & shape depend on object configuration and movement and direction of thrust.
• Edges are clean or slightly pointed and may have split- or fish-tail defects.
• Abrasions may or may not be present.
• Changes in notching suggest a shift in the knife's direction during the attack.

Incised Wounds

• Usually due to sharp instruments
• Length typically exceeds depth
• Wound margins remain uninjured
• Deep tissues are cleanly cut; examples include surgical incisions

Other Injuries

• Weals (reddening, swelling, normal response).
• Glass injuries.
• Axe/chop injuries (blunt and sharp).
• Thermal injuries.
• Firearm injuries.
• Defense injuries (forearms, hands, thighs).
• Fabricated/fictitious wounds (intentional).
• Self-inflicted wounds (suicide attempts and other deliberate actions).
• Understanding the characteristics of self-inflicted injuries.

Age of Injuries

• Assessing bruise progression, from purple to yellow over time.
• Determining the appropriate time frame for injury occurrences.
• Determining how scarring occurs and what methods are used for evaluation.

Death from Injuries

• Haemorrhage.
• Damage to vital structures.
• Shock.
• Infection.
• Pulmonary thromboembolism.
• Acute tubular necrosis.
• Fat embolism.

Fat Embolism Syndrome

• Occurs 12-72 hours after traumatic injury, common after pelvic and long bone fractures.
• Embolism of fat from bone marrow.
• Enters circulation via ruptured vascular sinusoids/venules.
• Clinically diagnosed by exclusion.
• Autopsy reveals fat in lung, brain, retina, and kidney.

Gunshot Injuries

• Type of weapon (rifled vs smoothbore).
• Distance from firing (contact vs. distance).
• Direction of shot.

Shotguns

• Single or double barrelled, repeating, semi-automatic types.
• Average barrel length (18-36 inches), and short barrelled (saun-off) weapons (10 inches or less).
• Characteristics of contact wounds (e.g., soot, powder, shot).
• Distance wounds (e.g., loss of contact abrasion).

Rifled Weapons

• Parallel grooves/lands inside the barrel (typically 4-7).
• Left/right twist imparts gyroscopic stability.
• Leaves marks on the bullet surface (rifling).

Rifle Weapon Injuries

• Features of entry wounds (neat hole, less than bullet diameter, soiling by bullet grease, abrasion collar, inverted edges),
• Secondary projectiles/fragmented projectiles/clothing.
• Contact wounds.
• Distance wounds (e.g., absence of bullet grease, soiling, discoloration).

Exit Wounds

• Can be more irregular than entry wounds.
• Usually larger than entry wounds with inverted edges.

Internal Injuries

• Tissue damage from projectile energy and speed.
• Shock waves that cause tissue damage from projectile impact.
• Shotgun pellets and tissue/bone stopping projectile.
• High velocity projectiles, crushing, and laceration of tissues.
• Temporary cavitation, stretching of tissues, fractured bones.

Road Traffic Collisions

• Causes (intoxication, human failings, natural disease, environmental).
• Driver, passenger, pedestrian injuries.
• Seatbelts and airbags (effect, law).
• Pedestrian injuries (primary, secondary, tertiary contacts).

Motorcycle Deaths

• Higher injury/death rate compared to car drivers.
• Common head/neck injuries (skull fractures, cervical spine fractures, cortical contusions/lacerations).
• Limb injuries (lacerations, friction burns, fractures).
• Trunk injuries (rib fractures, visceral damage).
• Tailgating accidents, brush abrasions, crush injuries.

Things to Remember

• Road traffic collisions (RTCs) in Ireland are typically Coroner's PM cases.
• Document and measure patterned injuries (bumper, headlights).
• Overall injury pattern is valuable, especially in conjunction with forensic crash investigations.