Forensic traumatology

Forensic traumatology is the branch of legal medicine dedicated to the systematic study and documentation of physical injuries caused by external mechanical, thermal, electrical, or radioactive forces. By identifying common pathological features and etiological markers, forensic traumatology allows for the accurate reconstruction of events and the essential differentiation between accidental, suicidal, and homicidal acts.

Blunt trauma is any nonpenetrating injury caused by the impact of a blunt object against the body, resulting in damage to underlying structures. Forensic evaluation focuses on the morphology of the wound to identify the striking surface and estimate the timing of the injury.

Abrasions

Abrasions are medicolegally significant as they often mirror the striking surface of the weapon.

Classification

Abrasions are classified based on the mechanism of injury:

• Tangential force
  • Scratch abrasion
  • Grazed abrasion: caused by direct rubbing or sliding against a surface
• Perpendicular force
  • Imprint abrasion: resulting from a momentary impact of an object against the skin (e.g., whip marks)
  • Pressure abrasion: caused by the application of sustained perpendicular pressure (e.g., ligature mark in hanging)
  • Patterned abrasion: an abrasion that clearly displays the shape or texture of the weapon used.

Medicolegal significance

Ageing

The color of an abrasion is used to estimate the time since injury.

Antemortem vs postmortem

Contusions

A contusion is an extravasation of blood into the surrounding tissue caused by the rupture of blood vessels after direct trauma.

Classification

By depth

• Superficial: extravasation of blood into subcutaneous tissues only
• Deep: extravasation of blood that occurs deeper than subcutaneous tissues; may not be immeditely visible

By location relative to impact

• Coup: ocated directly beneath the site of impact
• Contrecoup: located on the contralateral side of the site of impact
• Ectopic: located away from the site of impact

Medicolegal significance

Ageing

The color of a bruise is used to estimate the time since injury.

Assessing severity of injury

• The extent of a contusion may not be proportional to the intensity of the injury.
• Some factors influence the extent of a contusion.
  • Exacerbating factors (increase the extent)
    • Female sex
    • Old age
    • Preexisting conditions (e.g., hemophilia)
  • Mitigating factors (reduce the extent)
    • Male sex
    • Good muscle tone (e.g., in athletes)

Lacerations

A laceration is a tear or split in the skin or internal organs caused by crushing or stretching force. It is critical to differentiate lacerations from sharp-force incised wounds.

Classification

Lacerations are classified based on the mechanism of injury:

• Split lacerations: when the skin is crushed between a blunt object and underlying bone
• Stretch lacerations: caused by overstretching of the skin
• Avulsion lacerations: caused by a tangential force, "flaying" the skin or soft tissue away from the underlying bone or fascia
• Compression lacerations: when a heavy object moves across the skin, grinding it against the bone and causing irregular, ragged tears

Incised wounds

• Incised wounds are clean-cut injuries that are typically longer than they are deep.
• Differentiating features: Unlike blunt-force lacerations, incised wounds lack tissue bridges and exhibit clean-cut hair bulbs and margins.
• Tailing: The depth of an incised wound decreases toward its end. This "tailing" indicates the direction of the force applied during the cut.
• Specific types of incised wounds
  • Hesitation cuts (Tentative Cuts)
    • Multiple, superficial, linear cuts often found near a deeper, lethal wound
    • These are diagnostic of suicidal attempts.
  • Bevelling
    • When a blade enters the skin obliquely, creating undermined margins
    • Suggestive of homicide
  • Flap wounds: when a blade enters the skin horizontally
  • Lacerated-looking incisions: seen in skin folds (e.g., axilla or scrotum) or when a knife has a serrated edge

Stab wounds

• Weapon identification
  • Single-edge knife: Produces a wedge-shaped, triangular, or pear-shaped wound.
  • Double-edge knife: Produces an elliptical or spindle-shaped wound.
• Hilt mark: A patterned bruise or abrasion mirroring the knife's guard. Its presence indicates complete penetration of the blade into the body and helps determine the direction of force.
• Relation to Langer lines
  • Stabs parallel to Langer lines result in minimal gaping.
  • Stabs perpendicular to Langer lines result in maximum gaping.
• Lethality Factors: In stab injuries to the heart, the risk of fatality is inversely proportional to the thickness of the chamber wall (right atrium > left ventricle).

Special types of stab wounds

Concealed punctured wounds

• Small, deep wounds that may be intentionally or unintentionally hidden by natural body folds or orifices.
• Common locations include:
  • Axilla (armpit)
  • Nostrils and ears
  • Fontanelles (in infants)
  • Nape of the neck (often hidden by hair)
  • Anus and vagina

Hara-kiri/Seppuku

• A specialized form of suicidal abdominal stab wound involving a deep, horizontal incision followed by an upward cut
• Death results from evisceration and circulatory collapse

Chop wounds

• Chop wounds are caused by heavy instruments with a sharp edge, such as an axe or a meat cleaver.
• Morphology: Deep, wide wounds with regular margins
• Differentiating features: The floor of a chop wound often exhibits a cut-fracture of the underlying bone, which is diagnostic of a heavy, sharp weapon.
• Medicolegal significance: These injuries are almost always suggestive of homicide.

Defence injuries

• Defence wounds result from the victim's attempts to ward off a sharp-force assault.
  • Active defence: cuts found on the palms or the first web space of the hands as the victim attempts to grab the weapon
  • Passive defence: cuts on the extensor surfaces of the forearms or wrists as the victim attempts to shield their vital organs.
• Medicolegal significance: These injuries are usually indicative of homicide or an attempted homicide.

Skull fractures

For an overview of skull fracture classification, see "Cranial vault fracture" and "Basilar skull fractures" in “Skull fractures.”

Medicolegal significance

Puppe's rule

• Utilized to determine the sequence of multiple blows to the skull
• Principle: A fracture line resulting from a second blow will terminate when it reaches a pre-existing fracture line from a previous blow.
• Significance: It allows the forensic pathologist to prove which blow was delivered first, which is essential for reconstructing the sequence of an assault.

Mechanism of injury

• Depressed fracture
  • Often caused by objects with a small striking surface (e.g., a hammer)
  • The shape of the fracture often mirrors the striking surface of the object used - "signature fracture".
• Pond fracture
  • Subtype of depressed fracture
  • Also known as indented or ping-pong fracture
  • Seen in infants (< 4 years) due to their unossified skull bones
• Gutter fracture: associated with an oblique bullet
• Ring fracture
  • Fracture in the base of the skull around the foramen magnum
  • Results from a fall from height when the victim lands on their feet or buttocks, forcing the spine into the skull base
• Hinge fracture
  • Fracture that extends transversely across both temporal regions, dividing the skull base in two
  • Caused by massive lateral impact

Coup-contrecoup injury

• Occipital impact: results in frontal lobe contusion (most common contrecoup injury)
• Frontal impact: results primarily in coup (frontal) contusion; contrecoup injuries are typically absent.
• Temporal impact: results in contralateral temporal lobe contusion

Intracranial hemorrhage

For a detailed overview of intracranial hemorrhages, see "Epidural hematoma", "Subdural hematoma", "Subarachnoid hemorrhage", and "Intracerebral hemorrhage".

Autopsy findings

• Epidural hemorrhage
  • Does not cross suture lines
  • Blood clot is biconvex
• Subdural hemorrhage: hemorrhage clears when poured with water
• Subarachnoid hemorrhage: hemorrhage does not clear when poured with water

Medicolegal significance

• Lucid interval
  • Most common in individuals with an epidural hemorrhage
  • During lucid intervals, an individual may provide valid evidence, execute a legally valid will, or be held criminally liable.
• Medicolegal liability: A failure to diagnose or monitor a patient during a lucid interval may be considered medical negligence.

The forensic evaluation of transportation accidents focuses on reconstructing the mechanism of impact, identifying the position of the victims, and determining if safety restraints were utilized.

Occupant injuries

Injuries to vehicle occupants are determined by the point of impact and the specific interior components of the vehicle.

Pedestrian injuries

Reconstruction of a vehicle-pedestrian collision requires the identification of specific injury phases.

1. Primary impact injury: caused by the initial contact with the vehicle bumper or grille
2. Secondary impact injury: when there is a second contact of the victim with the vehicle (e.g., the hood or windshield).
3. Secondary fall injury: when the victim is thrown from the vehicle and strikes the ground
4. Run-over injury: caused by the vehicle passing over the victim’s body; characterized by grease marks or patterned tire tracks on the skin

The forensic investigation of an explosion focuses on the reconstruction of the event, the determination of the victim's orientation relative to the blast, and the identification of the explosive medium.

Classification by blast medium

The nature of the surrounding environment significantly dictates the resulting pathological patterns.

Airblast

• The most common explosion type
• Energy is transmitted through the air as a supersonic overpressure wave.
• For a detailed overview of airblast injury classification, see "Overview of blast injuries" in "Military medicine".

Underwater blast

• Due to the relative incompressibility of water, energy is transmitted with high efficiency directly to internal organs.
• Characteristic injury: massive damage to the gastrointestinal tract and other gas-containing hollow viscera

Solid blast

• Energy is transmitted through solid structures (e.g., floors or hull of a vehicle).
• Characteristic injury: multiple, complex, often symmetrical skeletal fractures of the lower limbs and pelvis

Injury reconstruction

• Mapping the distribution of flash burns and debris embedded in the skin allows for the determination of which side of the victim was facing the explosion.
• The degree of tympanic membrane damage serves as a biological indicator of the pressure level at the victim's location.

Forensic evidence collection

A critical component of the postmortem examination in explosion cases is the recovery of trace evidence for criminalistic analysis.

• Fragment recovery: All foreign objects (e.g., metal fragments, wires, or building materials) recovered from the body must be carefully labeled and preserved to assist in identifying the composition and design of the explosive device.
• Residue analysis: Swabs of the skin and clothing are collected to test for volatile chemical residues from the explosive agent.
• Postmortem gas levels: Analysis of carboxyhemoglobin (COHb) and cyanide levels is performed to determine if the victim inhaled toxic gases post-explosion, indicating they were alive in the immediate aftermath.

The forensic evaluation of electrical and lightning injuries focuses on identifying entry and exit wounds and recognizing pathognomonic markers of high-voltage and atmospheric discharge.

Electrical injuries

• The severity of an electrical injury is determined by the current type, frequency (Hz), voltage (V), and skin resistance. For a detailed overview, see "Electrical injury" in "Environmental pathology".
• Forensic relevance
  • Low-voltage injuries
    • Joule burn
      • The characteristic entry wound of a domestic or low-voltage current.
      • It features a central depressed, charred area with raised, erythematous margins.
    • Metalization
  • High-voltage injuries
    • Flash burn: A diffuse, superficial burn caused by proximity to a high-voltage arc.
    • Crocodile burn: Multiple punctate, charred lesions resulting from multiple points of contact or arcing.

Lightning injuries

• Lightning strikes involve a very brief (< 1 second) exposure to an intense (> 106 V) electrical discharge
• Characteristic findings
  • Lichtenberg figure
    • These are not true thermal burns but result from the extravasation of blood into the skin along the path of the electrical discharge.
    • They typically disappear within 24–48 hours in survivors.
  • Sledgehammer effect: The massive expansion of air (blast wave) can rip clothing and throw the victim, mimicking blunt-force trauma or an explosion.
  • Magnetization: steel objects carried by the victim (e.g., keys or watches) may become magnetized after a lightning strike
  • Victims may exhibit cadaveric spasm and rapid onset of rigor mortis.

The forensic evaluation of thermal injuries is primarily focused on determining the victim’s state of vitality at the onset of a fire and differentiating antemortem trauma from postmortem heat-related artifacts.

Evidence of antemortem exposure

External signs of vitality

• Crow’s feet
  • Soot-free radial lines extending from the lateral canthi of the eyes.
  • These occur because the victim tightly closed their eyes to protect them from heat and smoke.
• Vital blisters: characterized by an inflammatory (reddish) base and containing fluid rich in proteins and chlorides
• Red line of demarcation: a zone of hyperemia surrounding a burn, indicating a functioning circulatory system at the time of injury

Internal signs of vitality

• Carboxyhemoglobin (COHb): A COHb level > 10% in the blood is diagnostic of antemortem smoke inhalation.
• Airway soot: The presence of carbon (soot) deposition in the larynx, trachea, and deep bronchi indicates active respiration in a smoke-filled environment.
• Curling ulcers: Acute stress ulcers in the gastric or duodenal mucosa that may develop in individuals who survive the initial thermal insult.

Postmortem heat artifacts

Exposure to extreme temperatures produces physical changes that can mimic antemortem injuries, leading to potential misinterpretation of the manner of death.

Estimation of burnt surface area

• Accurate documentation of the total body surface area affected is required for both clinical and forensic evaluation.
• See "Extent of burn" in "Burns".

Lethal exposure to extreme ambient temperatures leads to systemic physiological failure. Forensic evaluation focuses on identifying pathological markers and characteristic behavioral patterns associated with hypothermia and hyperthermia.

Hypothermia

• Hypothermia occurs when the body's core temperature drops below 35°C. Forensic diagnosis relies on identifying signs of systemic shutdown and paradoxical behaviors.
• For expected clinical features of hypothermia based on core body temperature, see "Clinical features of hypothermia" in "Hypothermia and frostbite".
• Autopsy findings
  • Pink hypostasis: bright pink staining of the dependent parts of the body (resembling carbon monoxide poisoning), caused by the shift in the oxygen-hemoglobin dissociation curve in cold blood
  • Wischnewsky spots
    • Gastric mucosal petechial hemorrhages or erosions found in the stomach lining
    • Considered a diagnostic marker for lethal cold exposure

Heatstroke

• For a detailed overview of heatstroke, see "Heatstroke" in "Heat-related illnesses".
• Postmortem findings
  • Postmortem caloricity
    • A condition where the core body temperature remains elevated or continues to rise for a period after death.
    • This must be differentiated from other causes of high body heat, such as tetanus or septicemia.
  • Evidence of global visceral congestion and petechial hemorrhages, particularly in the brain and heart

• The forensic evaluation of radiation trauma focuses on reconstructing the duration and severity of exposure through the identification of pathological phases and characteristic dermatological markers.
• For a detailed overview of radiation injuries, see "Radiation injury".
• Autopsy findings in fatal exposure
  • Bone marrow: serous atrophy or total depletion of hematopoietic cells
  • Visceral hemorrhages: widespread petechial and ecchymotic hemorrhages in the internal organs due to radiation-induced thrombocytopenia
  • Lymphoid atrophy: marked shrinkage of the spleen and lymph nodes