FPY1-2 Examination of Wounds and Injuries by Forensic Pathologist

Definitions and Terminology

  • Trauma: Derived from the Greek word for 'a wound'. Modern definitions encompass:

    • An injury to living tissue caused by an extrinsic agent.

    • A disordered psychic or behavioral state resulting from mental or emotional stress or physical injury.

  • Wounds: Specifically defined as the disruption of the continuity of tissues by external mechanical force.

  • Injuries: A broader term that includes damage produced by physical agents such as heat and electricity.

    • Note: In legal contexts, an 'injury' may also refer to a 'wrong'.

    • In practice, the terms trauma, wound, and injury are often used interchangeably.

Classification of Wounds

Wounds are categorized into several primary types based on their presentation and mechanism:

  • Abrasion (graze, scratch)

  • Bruise (contusion)

  • Laceration

  • Incised wound (cut wound)

  • Stab wound

  • Firearm wound

Abrasions

  • Definition: A disruption of the continuity of the most superficial layers of the skin.

  • Clinical Presentation: Usually trivial, painful, but involves very little bleeding.

  • Types Based on Mechanism:

    • Tangential Friction/Sliding Abrasions: Caused by tangential force.

      • Scratch: Linear marks.

      • Graze: Occurs when a body part skids across a rough surface tangentially.

      • Friction Burn: Caused by high-intensity friction.

    • Direct Impact/Patterned Abrasions: Caused by direct vertical impact.

  • Forensic Importance:

    • Reflects the exact site of impact.

    • Indicates the causative surface or object (patterned abrasions).

    • Indicates direction of force via the "heaping up" of skin tags at the distal end of the wound.

    • Postmortem changes: Abrasions turn darker in color and become leathery after death.

    • Specific patterns include Fingernail scratch marks, which have a characteristic curvilinear appearance.

Bruises (Contusions)

  • Definition: Blunt force injuries characterized by the leaking (extravasation) of blood from damaged blood vessels in the connective tissue of the skin or deeper underlying tissues.

  • Mechanisms of Production:

    1. Blunt Force Impact: Such as a blow (hitting) or a fall (bumping). Examples include slapping (finger segment marks) or landing on the back of a hand during collapse.

    2. Squeezing/Pinching: Force is applied gradually and maintained. Examples include paired finger-tip bruises or linear intradermal bruises between them.

    3. Suction: Known as "hickies," "love-bites," or cupping. These present as punctate hemorrhagic spots that merge into a confluent bruise.

  • Types of Bruises:

    • Ordinary Bruise: Extravasation arises in the deeper dermis and extends into subcutaneous tissue. The outline at the skin surface is typically blurred or indistinct.

    • Intradermal Bruise: Bleeding occurs more superficially. Components are easily delineated (punctiform, sharply defined, and bright red). These frequently retain the "pattern" of the object (e.g., grooves or ridges of a weapon).

    • Deep Bruise: May take 1212 to 2424 hours to appear at the skin surface, or may never appear at all. In the living, a second exam after 1−21-2 days is recommended; in the dead, a further exam 1−21-2 days after the original autopsy may reveal previously invisible bruises.

  • Significance and Limitations:

    • Gravity: Extravasated blood tracks along natural planes and is affected by gravity; the bruise may appear at a site distant from the actual impact.

    • Object Identification: Shape and size are generally poor indicators of the causative object, unless it is an intradermal/patterned bruise.

    • Severity Factors: Degree of force is roughly proportional to size, but severity depends on site, age, obesity, disease, and skin color.

  • Aging of Bruises:

    • Color changes occur due to hemoglobin breakdown: Reddish-blue $\rightarrow$ purple $\rightarrow$ brown $\rightarrow$ green $\rightarrow$ yellow $\rightarrow$ straw.

    • Yellow color indicates the bruise is more than 1818 hours old. Age estimation must be attempted with caution.

  • Postmortem Bruises: Can be formed up to 88 hours postmortem (idiomuscular pad investigation), showing characteristic "tram-like" hemorrhages.

  • Classical Patterns:

    • Tyre Marks: From road traffic collisions.

    • Finger Pad Bruises: Often seen in child abuse.

    • Tramline Bruises: Produced by a rod/stick where blood vessels at the edges are stretched/bleeding while the center is compressed/no bleeding.

    • Black Eye (Periorbital Bruise): Also referred to as "Racoon eyes sign."

Lacerations (Split Wounds)

  • Definition: A full-thickness tear of soft tissue caused by blunt force trauma, distinct from sharp force incisions.

  • Mechanisms:

    • Perpendicular Crushing Force.

    • Tangential Shearing Force: Often combined with crushing (e.g., a rotating vehicle wheel running over a limb).

    • Over-stretching: E.g., upper calf lacerations in a fall from height (FFH) where the individual lands on their feet.

  • Characteristics:

    • Irregular margins, often bruised and abraded.

    • Tissue Bridging: Crucial diagnostic feature; bridges of blood vessels and nerves remain intact across the wound.

    • May be mistaken for cut wounds when occurring over bony prominences (e.g., the scalp).

  • Forensic Importance:

    • Trace evidence may be found within the wound.

    • Shape and size are not usually related to the causal object.

    • Crescent-shaped lacerations may indicate specific blunt impacts.

Cut Wounds (Incised Wounds)

  • Definition: Wounds caused by sharp-edged instruments.

    • Chop Wounds: Cut wounds produced by heavy instruments (e.g., a chopper/cleaver), which may leave distinct marks on bone (e.g., chopper marks on skull).

  • Forensic Importance: Danger to life depends on site/depth. They can be accidental, assault-related, or self-inflicted.

  • Self-Inflicted Cuts:

    • Often associated with emotional distress, trauma, or suicidal gestures.

    • Sites of Predilection: Anterior aspects of the body, specifically wrists, neck, and groin (where pulses are felt).

    • Tentative Injuries (Hesitation Marks): Superficial cuts made before the final fatal injury.

    • Suicidal Characteristics: Usually accessible, parallel or overlapping cuts, no involvement of sensitive features (eyes/ears), and clothing is typically not involved.

  • Defensive Injuries: Repetitive injuries, often on the back of the forearm or hands, indicating a struggle.

  • Assault Cuts: Tend to be haphazard, criss-crossing, and may involve any site.

Stab Wounds

  • Definition: Penetrating wounds where the depth (D)(D) of the wound track is greater than the length (L)(L) of the surface wound (D > L).

  • Wound Interpretation:

    • Wound Track Depth: Not an exact indicator of weapon length (especially in the abdomen due to compression), but the deepest wound in a series is a guide to the minimum length.

    • Wound Length: Measured with edges approximated. Skin elasticity usually makes the wound slightly smaller than the weapon width.

    • Degree of Force: Depends primarily on the sharpness of the weapon tip; resistance is highest at the skin and clothes.

Forensic Ballistics (Gunshot Wounds)

  • Subdivisions: Interior (inside firearm), Exterior (muzzle to target), and Terminal/Wound Ballistics (target effects).

  • Principle of Firearm: Trigger pull $\rightarrow$ propellant explodes $\rightarrow$ hot gases/flame/smoke/powder $\rightarrow$ projectile ejected.

  • Entrance Wounds (Handgun):

    1. Contact Wound: Central skin defect; margins split, scorched, and blackened; central abrasion ring (1−3 mm1-3\,mm); underlying tissue tinted "cherry-red" by carbon monoxide.

    2. Near-contact (< 1\,cm): Seared skin surrounded by a wider band of soot deposition. Within arm's reach (over 6"6"), there may be a split entry and scattered powder tattooing.

    3. Intermediate Range: Features "stippling" or "powder tattooing" around the entry wound. Area of stippling increases while density decreases with distance.

    4. Distant (over 2−3 feet2-3\,feet): Only an abrasion ring around a central perforation; no soot or stippling.

  • Exit Wounds: No skin defect (margins can be aligned); no abrasion ring; edges are frequently irregular, torn, or everted (bulging out).

  • Bullet Wound Tract:

    • Permanent Cavity: Primary wound channel caused by direct tissue damage.

    • Temporary Cavity: Created by the stretching of the permanent cavity due to energy transfer; collapses after the bullet passes due to elastic recoil. Not identifiable at autopsy, but damaging effects to surrounding organs are visible.

  • Manner of Death:

    • Suicide: Almost always contact/near-contact wounds. Elective sites: right temple (or left for left-handed), center brow, mouth, or heart.

    • Detection: Recent holding of firearms can be detected using PDT (ferrozine spray), which forms a magenta-colored complex if iron residue is present on the hand.

Examination and Evidence Protocol

  • Clothing: Retain clothing and "contact traces."

  • Chain of Custody: Hand evidence directly to police; ensure they sign for continuity.

  • Weapon Matching: Do not attempt to fit a weapon into a wound, as this contaminates the weapon with blood and alters the wound's characteristics.

  • Fictitious/Factitious Wounds: Usually superficial, accessible, and relatively harmless cuts meant to simulate assault or for other secondary gains.