Forensics & autopsy
Types of injuries
Asphyxia
Author: Lindsey Harle, M.D.
Topic Completed: 1 June 2012
Minor changes: 26 August 2019
Copyright: (c) 2012-2019, PathologyOutlines.com, Inc.
PubMed search: Forensic [title] asphyxiation
Table of Contents
Definition / generalCite this page: Harle L. Asphyxia. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/forensicsasphyxia.html. Accessed August 6th, 2020.
Definition / general
- Asphyxia is the lack of oxygen supply to tissues/organs
- Types of asphyxia include suffocation, strangulation / hanging, positional / mechanical / traumatic
Suffocation
- 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
