You can read the first three parts here:
Asphyxiation occurs when a person's oxygen supply is cut off and air is unable to reach the lungs and hence the rest of the body. The methods of asphyxiation we’re talking about today are hanging and strangulation. Accidental strangulation is most often achieved through auto-erotic asphyxiation in which the victim chokes themselves (or has a partner do it) in order to achieve orgasm. I’m not going to talk about it that much in this post because the symptoms on the body are very similar.
Death by hanging is an ancient form of punishment that was popularized in the old west. A rope is tied around the victim’s neck and they are dropped suddenly from a height, death resulting from a broken neck. However, if the length of rope is incorrect, death can be caused by suffocation or decapitation. Other variants include the victim being lifted by the noose already around their neck, resulting in death by suffocation. Suspended hanging involves little to no drop in which death occurs by compression of the trachea and/or the major blood vessels connecting the heart (carotid arteries) and the brain (vertebral arteries).
Strangulation is constriction of the neck without suspending the body either by ligature or manually (by hand). Sudden and violent compression of the windpipe (with a strong hand, or a rope) will cause almost immediate death however if the windpipe is only partially closed, buzzing in the ears, vertigo, muscle weakness, bleeding from the mouth, nose and ears and convulsions can occur. The victim will usually lose consciousness before death, sometimes confusing the killer into leaving them alive. A clear indication of strangulation is the distinct mark left on a person’s neck, a bruise from the weapon used – although a soft ligature will produce pale marks that may not be distinguishable. In cases of hanging the mark will an upward u-shape from just under the chin tilting back towards the ears, whereas manual and ligature strangulation will vary depending on the height and strength of the killer but are usually distinguishable from hanging by being horizontal across the throat.
Signs of mechanical violence (manual strangulation) include fracture of the larynx or hyoid bone, bruising of the muscles and visible impressions on the skin, and petechiae (or petechial hemorrhaging) which are pinprick points of bleeding where the blood vessels have ruptured around the eyes and eyelids, easiest to detect in the whites of the eyes. When a person’s airflow is cut off or restricted (smothering, suffocation, strangulation) the body struggles to breathe and move oxygenated blood to the vital organs. This increased pressure can be too much for the blood vessels and they simply burst open. Of course this symptom is not exclusive to strangulation; it can be seen in victims of drowning or even heart failure. In cases of homicide it’s common to see fingernail marks around the victim’s neck where they tried to claw their way out. The thumb generates more pressure than the other fingers so often that is the only impression (or the most noticeable impression) found.
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