The term Mechanical asphyxia is coined where enough external pressure is applied to neck, chest or other areas of body or position of the body is in such a way that respiration is impossible.¹ Asphyxia is defined as lack of oxygen in blood and tissue due to impaired or absence of oxygen leading to death².Death due to fatal neck compression falls in the category of mechanical Asphyxia – which includes suicidal hanging, strangulation, throttling, Mugging, Bansdola etc. and failure to expand chest by any obstruction leading impossible to breathe is also mechanical asphyxia, namely traumatic asphyxia. In all such cases hypoxia in the brain occurs rapidly leading to death. WHO mortality data found that hanging was the most common method used for committing suicide in most of the countries.³ Literature study suggests that the suicidal hanging is the most common method used in India. Hanging is a type of mechanical asphyxia where complete or partial suspension results weight of the body to act as force for compression of neck tied by a ligature around the neck.⁴ Whereas Strangulation is another form of violent asphyxia result from  constriction of neck by other means except the force of constriction due to victim’s own body.⁵Hanging is the preferred method of suicide because it is easy to carry out and only a ligature material is required in the form of a rope saree, dopatta, dhuti, lungi etc. which are easily available. On the other hand, Strangulation noticed as the most common form of suffocation as per expert opinion of forensic specialist⁶. According to position of body Hanging may be classified as Complete and Incomplete. For complete hanging, body is completely suspended from the ligature, with no part of the body touching the ground where in Incomplete hanging body is partially suspended, person may be in sitting, kneeling or toes or feet touching the ground.⁷ But according to position of knot Hanging may be Typical & Atypical. Typical hanging where ligature runs from the midline of the neck, above the thyroid cartilage, and ends at the occipital region and knot is in the middle of the back of the neck. In case of Incomplete hanging position of knot is located anywhere other than the middle of the back of the neck, such as near the mastoid process, angle of the mandible, or under the chin etc.^6,7 Knot may be slip or fixed knot, by which hanging may be typed another way. Examination of knot abrasion along with patterns of bruising over tissue layers of neck, underneath the ligature may help to find out exact nature of force applied during compression of neck.² The term ‘Laryngo-hyoid Complex’ is coined frequently referring hyoid bone and thyroid cartilage as together. In case of violent compression neck these two structures are found the most susceptible to be fractured and/or injured. Longer and wider hyoid bone is comparatively more damaged than shorter and smaller one⁸.Thus detailed analysis of the victim’s injury pattern along with finding out the cause or manner of death can be utilized for medico legal investigation in future for similar type of cases.

AIMS & OBJECTIVES:

1. To determine changes in neck structures
2. To determine cause of compression, and manner of death
3. To determine characteristic changes in particular type of compression
4. To determine influence of ligature material used
5. To evaluate the incidence of hanging and strangulation
6. To evaluate the common victims of hanging and strangulation as regards to their age, sex, religion, position of knot etc.

MATERIALS AND METHODS

This Observational, Descriptive and Analytical study was carried out in the Mortuary of Department of Forensic Medicine & Toxicology of RGK Govt. Medical College of Kolkata, West Bengal for one year period i. e. 01.04.2015 to 31.03.2016. Post mortem study was carried out in 100 cases of death due to compression of neck.

Method of sampling technique -Sample size was decided applying statistical formula –

N= z² x p (1-p)/e², [N= Sample size, z= z score for 95% confidence level, p= population proportion & e= margin of error]. Applying the above formula, taking margin of error as 5%, population proportion as 7.2 %, and z score for 95% confidence level as 1.96, sample size is calculated as:

N= 1.96² x 0.072 (1- 0.072) / 0.05^{2 =} 102.67.

Two (2) Dead bodies in highly decomposed condition with loss of neck tissue were excluded from the study.

For convenience total 100 cases in that period ware selected as study subject

A thorough history from police and family members of the deceased related to the unfortunate incidence ware taken. Information from Inquest report regarding scene of crime, position of body, material used, etc. were taken Ligature marks in different cases where available, ware observed meticulously for different parameters like length, width, shape, position in neck, continuity, change of skin color underneath etc. Any fracture of neck bones or cartilages also tried to detect carefully not only by palpatory method but applying special tests. All data were collected, compiled and subjected to suitable statistical analysis using appropriate methods. The obtained data were displayed as frequency and percentage in figures and tables.

RESULTS

Among the victims, majority (52) of them belonged in the age space of 21-40 yrs, with 15 of them being in between 10-20 yrs and 24 of them being in between 41-60 yrs.

According to position of knot most cases comes under Atypical hanging (82), whether Typical Hanging in only 12 cases. Partial Hanging is noted in 6 cases only.

The position of Ligature mark situated above thyroid cartilage in maximum case, where 14 cases it found just at the level of thyroid cartilage. Only 4 cases it situated below thyroid cartilage.

Patterned bruise underneath the ligature mark present in only in 11 cases.

In majority of cases the tissue underneath the ligature mark noted as pale, white, glistening, whereas only mild congestion underneath the ligature mark found in 13 cases.

Rupture of Sternomastoid mostly absent, only in case rupture or tear of sternomstoid noted.

No fracture of hyoid and thyroid bone seen in maximum case (82) but 6 cases fracture of hyoid and 12 cases of fracture of thyroid in noted.

As per manner of neck compression mostly suicidal (82) where in 18 case it was found to be homicidal

Table 1: Age wise distribution of cases:

Figure 1: Cases According To Type of Hanging

Figure 2: Position of ligature mark

Figure 3: Cases according to patterned bruise at the ligature mark

Figure 4: Cases according to condition of the underneath tissues of the Ligature Mark

Figure 5: Cases according to rupture of Sternomastoid muscle

Figure 6: Cases according to Fracture of Hyoid &Thyroid

Table 2: Case distribution according to manner of neck compression

DISCUSSION

Study conducted by Meera Th ⁹ showed similar findings about age group (31-40) yrs which found to be mostly affected in present study.

Our study showed atypical hanging is the commonest (82%) followed by typical and partial hanging. This finding was corroborated in study done by Saisudheer T¹⁰

Regarding level of ligature mark, in most of the cases the ligature mark presents high up in the neck above thyroid (82%), placed obliquely and non-continuous whereas study Ma J¹¹ found it 88% in his study. During suicidal hanging the working body weight is the main constricting force which leads the noose high up. Reddy ¹ mentioned about ligature mark in hanging mostly  (80%) situated above the level of thyroid cartilage, between larynx and chin. 15% cases may be situated at the level of thyroid cartilage and 5% cases, specifically in partial hanging ligature mark situated below the level of thyroid cartilage.

Non continuous along the course of the ligature mark is crucial character differentiating between the ligature marks of hanging verses strangulation by ligature.

The internal appearance of underlying soft tissues of neck was found mostly pale, white and   glistening among cases of hanging while few cases showed extravasations of blood. Most victims (87%) did not exhibit “classic signs of neck compression” ¹²ie congestion associated with petechial hemorrhages. Classic signs are purely mechanical vascular phenomena arise from obstructed venous return. Increasing pressure in venules and capillaries leads to rupture in areas of minimal connective tissue support, like the conjunctivae and eyelids result formation petechiae.^{13, 14}

Rupture of muscle fibers of sternomastoid was found in 20% of cases of total victims which corroborate with the study conducted by Jaya prakash S¹⁵with little difference.

Incidence of fracture of hyoid bone and laryngeal cartilages varies from 2% to 40% in different studies. Greater cornu was mainly damaged in neck compression. Md. Musaibet ¹⁶ and Jaya prakash S ¹⁴ observed these incidences of fracture of hyoid and thyroid cartilage 4.5% & 8.6% and 2.7% & 5.3% respectively, which ware different from present study. Fracture of cricoids cartilage, tracheal rings and cervical vertebrae were not seen in any cases, similar to observation of study by Meera Th⁹. Fracture of hyoid bone and laryngeal cartilage is of practical interest because it can be correlated with radiological findings.¹⁷

Majority of cases of hanging, on the basis of circumstances of death and postmortem findings the manner of death was suicidal, similar to the findings found by Taktak S¹⁸ in his study.

CONCLUSION

In the scenario of alarming increase in number of Suicidal hanging due to the effects of unemployment, poverty, family issue, addiction etc., thorough screening of vulnerable persons and timely intervention by psychological counseling and behavioral therapy for prevention of suicide may be the appropriate approach. The uniqueness of this study is that providing specific Post mortem findings in different types of cases of fatal neck compression forensic experts may help in clarification on dilemma in differentiating between cases of Hanging and strangulation by ligature which in turn will be beneficial to the police and justice department.

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