Autopsy & forensics

Types of injuries


Topic Completed: 1 June 2012

Minor changes: 15 November 2021

Copyright: (c) 2012-2019,, Inc.

PubMed search: Forensic [title] asphyxiation

Lindsey Harle, M.D.
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Table of Contents
Definition / general
Cite this page: Harle L. Asphyxia. website. Accessed December 3rd, 2021.
Definition / general
  • Asphyxia is the lack of oxygen supply to tissues/organs
  • Types of asphyxia include suffocation, strangulation / hanging, positional / mechanical / traumatic
  • Definition: failure of oxygen to reach the blood

  • Smothering: obstruction of nose and mouth
    • Accidental: infant wedged between mattress and wall
    • Suicidal: placing plastic bag over one's head and tightening around neck
    • Homicidal: duct tape across nose and mouth, covering face with pillow, closing off nose and mouth of young child with hand
    • Overlay: infant death due to parent onto child in bed; involves smothering and mechanical asphyxia
    • No specific autopsy findings; may see signs of struggle (contusions/abrasions on face and mouth) in adult victims

  • Choking: blockage of internal airways
    • Accidental: large food bolus in airway, usually intoxicated adults, elderly with neurodegenerative disorders, young children
    • Homicidal: gag placed in oropharynx
    • Must find food bolus or other item in airway, or have report of its prior removal, to confirm choking

  • Environmental: inadequate oxygen in atmosphere; also called entrapment
    • Due to oxygen displacement by other gases (in silo), lack of oxygen in small enclosed space (child trapped in refrigerator)
    • No specific autopsy findings
Strangulation / hanging
  • Definition: external pressure on neck resulting in compression of blood vessels and occasionally airway

  • Strangulation: neck compression due to something other than the victim's body weight, such as manual compression or ligature tightened by assailant; usually homicidal
    • Ligature strangulation: the ligature mark on the neck is usually horizontal
    • If homicidal (most common), may be signs of struggle (abrasions / lacerations and fingernail marks on neck)
    • Suicidal strangulations can occur if individual ties cord or other ligature around neck with some sort of locking device
    • Accidental strangulations can occur if scarf or necktie becomes trapped in doorway or other mechanical device

  • Hanging: neck compression due to ligature around neck, with at least a portion of body weight being used to tighten ligature
    • Usually suicidal; can be accidental (child trapped in cord) or homicidal
    • Ligature mark on neck is oblique, with highest point usually at back of head, where ligature knot is tied
    • This is in contrast to strangulation (usually homicide), where ligature mark is usually horizontal around neck
    • Ligature mark may be absent if soft fabric (i.e. bed sheet) used as ligature
    • May see pattern markings in ligature mark that correspond to patterns on ligature (i.e. weaved fabric, metal chain)

  • 4 pounds of pressure required to occlude jugular veins (preventing venous drainage of head) and 5 - 11 pounds to occlude carotid arteries
  • Loss of consciousness occurs in 10 - 15 seconds; death within 3 - 5 minutes
  • May see facial and conjunctival petechiae at autopsy
  • Fractures of hyoid bone, tracheal cartilage, cervical vertebrae are rare; hemorrhage in neck muscles also rare
  • Hyoid fractures are more common in older victims, because hyoid bone is cartilaginous and incompletely ossified in children and young adults
  • Injuries are more common if struggle between decedent and assailant
  • In hanging, where body is completely suspended, autopsy may show congestion and petechiae of lower legs due to blood pooling
  • May have no specific findings at autopsy
Positional / mechanical / traumatic asphyxia
  • Definition: position of body or external pressure on chest prevent respiration

  • Positional asphyxia: body is positioned in a way that restricts airflow
    • Twisting or compression of neck resulting in occlusion of oropharynx or trachea
    • Seen in intoxicated individuals or elderly persons who become trapped

  • Mechanical / traumatic asphyxia: external compression of chest, preventing normal respiration
    • Example: vehicle collapsing on individual working under car
    • May have petechiae, face and upper chest congestion at autopsy

  • Chemical asphyxia: gases that prevent oxygen utilization at cellular level
    • Carbon monoxide, hydrogen sulfide, cyanide
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