Strangulation is that form of asphyxia which is caused from constriction of the neck by ligature without suspending the body. Pulling a U-shaped ligature against the front and sides of the neck while standing at the back can cause death. It is of two types:  Strangulation by a ligature, and  manual strangulation or throttling.
Symptoms: sudden and violent compression of the windpipe causes almost immediate insensibility and death. If the windpipe is partially closed, buzzing in ears, congestion and cyanosis in head, vertigo, tingling, muscle weakness, bleeding from the mouth, nose and ears, clenching of the hands and convulsions occurs before death.
Cause of Death: Death may be due to (1)asphyxia, (2)cerebral anoxia or venous congestion, (3)combined asphyxia and venous congestion, (4)vagal inhibition,and (5) rarely fracture-dislocation of cervical vertebrae.
1] Whether Death was caused by Strangulation?
In death due to strangling, the general features of asphyxial death are present. Their local distribution in the head and neck is strongly presumptive of strangulation. This is confirmed by the ligature mark on the neck. Evidence of violent compression or constriction of the neck during life is obtained from the presence of bruising or ecchymoses about the marks on the neck, haemorrhages in the strap muscles, under the skin, in the sides of the tissues around the trachea and larynx, in the larynx and in the laryngeal structures themselves. The ligature mark alone is not diagnostic, for it may be indistinct or absent, if a soft ligature material is used. The ligature mark may be produced by the application of a ligature to the neck even after death. Certain marks on the neck produced after death may simulate ligature mark. The possibility of other causes of suboxic or asphyxial death should be excluded. In the absence of ligature mark in the neck or deeper injury, it will be difficult to form an opinion, except from circumstantial evidence. In cases of putrefaction, a medical opinion about strangulation can be given fairly, if there are signs of mechanical violence applied to the neck, e.g., fracture of the larynx or hyoid bone, bruising of the muscles and visible skin impressions. Indistinct marks on the neck, patches of discolouration or signs of asphyxia cannot be relied upon as evidence of strangulation in a putrefied body.
2] Whether the Strangulation was Suicidal, Homicidal or Accidental?
- Suicidal Strangulation: Suicide by strangulation is rare. Various methods of tightening the ligature are employed by the victims. The number of knots, tightness and method of knotting should be considered. Sometimes it is tightened like a tourniquet, but the person can apply a single or double knot, before consciousness is lost. In most cases, some mechanical device is always made to keep the ligature tight after insensibility develops. Several turns of rope are tied round the neck with the side or back of the neck. A cord may be tied around the neck and twisted tightly by means of a stick or some other solid material used as lever. When consciousness is lost, although grip on stick is released, the ligature will not become loose as it gets arrested against the shoulder or chin. In some cases, a running noose is applied to the neck, and the free end of the rope to which a weight is attached, is thrown over the end of the bed on which the victim lies. A person may strangle himself by leaning with the whole weight of his body on a cord passed round the neck and attached to a fixed point.
In suicidal strangulation, the signs of venous congestion are very well developed above the ligature, and are especially prominent at the root of the tongue. This severe congestion probably results by the slow tightening of the ligature, and also because it is usually so secured that it remains in place after death, preventing post-mortem drainage of blood. Injuries are usually less marked because less force is used. In all cases of suicidal strangulation, the ligature should be found in situ, and the body should not show signs of violence or marks of struggle. If ligature is still present, the number of turns and type of the knots require detailed study. The application of ligature with several turns, whether closed with a half-knot or even a complete knot, is consistent with suicide. A correct medical opinion may be usually formed from the course and direction of the tie, the way in which it was secured or fixed to produce effective pressure on the windpipe, and the amount of injury to the muscles and parts beneath.
Homicidal Strangulation:Strangulation is a common form of murder. Many of the victims are adult women and frequently strangulation is then associated with sexual interference. Usually there is a single turn of ligature round the neck, with one or more knots (granny or reef knots) at the front or side of the neck. When there are two or more firm knots, each on separate turns of the ligature, homicide is almost certain. There may be more than one ligature mark, each of varying intensity and crossing each other, in parallel or at an angle to each other. Abrasions are usually seen due to movement of the ligature across the neck. Fingernail marks may be seen, either from the victim attempting to remove the ligature, or from the assailant attempting to secure the ligature, and/or restrain the neck from moving, or even attempting manual strangulation. The victim’s clothing may sometimes be caught in the ligature during a struggle and produce marks, which require careful evaluation. The mark may either completely encircle the neck or may be seen only at the front, when the ligature is pulled tightly from behind. The mark may also be sloping if the ligature is pulled upwards from behind, and the position is high up at the level of the hyoid bone. Sometimes, a ligature is passed over the body, and then tied to the hands and feet to simulate suicide. In such cases, the manner of tying should be examined. Infanticide by strangulation may be caused by winding the umbilical cord round the infant’s neck. In such cases, the cord will show appearances indicative of rough handling with displacement of Wharton’s jelly, and other signs of violence are present on the body. The presence of a complex type of knotting in the cord, e.g., the presence of reef knot, suggests homicidal strangulation. Sometimes, homicidal strangulation is feigned by an individual to bring a false charge against his enemy. Hysterical women sometimes feign it without any obvious motive.
Evidences of struggle are usually found, but if the person is taken unawares, and the ligature is suddenly placed around the neck and pulled tightly, the person loses consciousness quickly and is unable to offer much resistance. If the person is weak and infirm, or made unconscious by blows on the head or by intoxicating drugs and in children, there may be few or no signs of struggle. If the clothing of the deceased is torn or disarranged, it indicates that a struggle has taken place. If there is a struggle, both assailant and victim may show abrasions and contusions.
Strangulation should be assumed to be homicidal until the contrary is shown. As a rule, the murderer uses for more force than is necessary, and as such, injuries to the deeper structures are well marked. If the ligature is around the neck with two or three knots at the back of the neck, it is presumptive of homicide. The ownership of the ligature may sometimes become an important clue, e.g., if the ligature found around the dead body may be proved to correspond with parts of the same material found in the possession of suspected assailant. Unusual ligatures may narrow the search for the assailant, since they may be material of the kind used in a particular occupation. If the ligature is removed or lies loose, unless explained, are presumptive of homicide. If the ligature mark of occhymosis in the neck does not accurately correspond with the ligature found, it is presumptive of homicide. Sometimes, circumstantial evidence, such as time, place, locked doors, and windows, motive, etc., is almost the only ground for a suggestion either of suicide or homicide.
Ligature marks produced after death do not show bruising. Either a grooved impression is seen on the skin which is not injured, or yellow or brown abrasion without signs of vital reaction. There may be ligatures or other marks around the limbs especially wrists and ankles, which may be placed either before or after death.
The common methods of homicidal strangulation are: (1) strangulation by ligature, (2) throttling, (3) bansdola, (4) garroting, and (5) mugging.
Accidental Strangulation: Children may get entangled in ropes during play, or the neck may be caught in window cords, etc. infants are sometimes strangled in their cots when the neck is caught inside bars, in restrainers, braces, etc. Occasionally, an infant is strangled with a string attached to a toy tied to the crib. Persons under the influence of alcohol, epileptics, and individuals with mental challenges may be strangled either by a tight scarf or collar and neck tie. It may occur if an intoxication person rests the neck against a bar or other hard object. It may occur when a string used in suspending a weight on back, slips from across the forehead and compresses the neck. In industry, belts, ropes or parts of clothing may be caught in the rollers or other parts of the moving machinery and cause accidental strangulation. Accidental strangling may occur in uterus when the movement of the foetus causes the umbilical cord to encircle the neck. In such case, there is relatively slight cervical tissue injury. Wharton’s jelly is not damaged and lungs are usually incompletely expanded. In a charge of murder, it may be suggested that the deceased might have been accidentally strangled in a state of intoxication, either by a tight scarf or collar and tie. When there is pressure on the windpipe, the victim attempts to pull the ligature, and scratches may be found on the neck, which may arouse a suspicion of throttling. If the relations of the body to surrounding objects and the constricting agent have not been disturbed, cases if accidental strangulation present no difficulty. If the body has been removed from the place in which it was first discovered, or the ligature has been removed, the presumption of accident can only be established from the description given.