If the throat is compressed by hands (strangulation), lower arms (carotid sleeper, headlock) or with the use of ligatures (hanging, throttling), this will constrict the cervical vessels and/or the air transportation system, causing an interruption of the air supply to the brain and ultimately leading to death. Depending on whether the compression restricts primarily the vessels or the air transportation system and on which vessels and with how much intensity, there may be widely varying findings from which expert conclusions can be drawn.
The anatomical circumstances should be recapitulated in order to reach a better understanding of the various findings from the different compression mechanisms.
The oxygen to the brain is supplied by four vessels, the carotid arteries located left and right at the front of the neck and the significantly smaller vertebral arteries which are deeper lying and relatively protected. Compression of the two carotid arteries is enough to cause death as the vertebral arteries alone cannot convey sufficient oxygen to the brain.
The veins carrying the used blood from the brain back to the heart are closer to the surface than the arteries which convey oxygenated blood to the brain. This means that during the strangulation process the flow of blood from the brain is the first to be interrupted and the stoppage of the blood supply to the brain is secondary. If both processes are not simultaneous or if the return blood flow rather than the blood supply is cut off, there will be signs of congestion above the area of compression. This can be invariably expected if, either during strangulation, the cervical arteries were not constricted or the compression was only light.
While loss of consciousness is rapid if the carotid arteries are compressed, the constriction of the air passages will lead to an excruciating fight for survival.