Manual strangulation is produced by pressure of the hand, forearm, or other limb against the neck, compressing the internal structures of the neck. The mechanism of death is occlusion of the blood vessels supplying blood to the brain i.e., the carotid arteries. Occlusion of the airway probably plays a minor role, if any, in causing death. Virtually, all cases of manual strangulation are homicide. In the authors' experience, it is the second most common method of homicidal asphyxia. In a study by DiMaio of 41 deaths caused by manual strangulation, females predominated, with the ratio of females to males 1.9 to 1 (27 to 14).26 Of the 27 females manually strangled, the motive was rape in 14 cases and domestic violence in 10.
One cannot commit suicide by manual strangulation because, as soon as consciousness is lost, pressure is released and consciousness regained. A choke hold can result in manual strangulation if it is maintained long enough.
Occasionally, it is claimed that the death of a healthy individual ascribed to manual strangulation is unintentional and caused by a vasovagal reaction (reflex cardiac death) brought on by touching, grasping, or striking the neck. This is an interesting theory, but unproven by objective evidence. The mechanism of death in such a case would be an arrhythmia produced by stimulation of the carotid sinuses. The carotid sinus is a focal area of enlargement of the common carotid artery where it bifurcates into the external and internal carotid arteries. Compression or stimulation of the carotid sinuses causes an increase in blood pressure in these sinuses with resultant slowing of the heart rate (bradycardia), dilatation of blood vessels (vasodilation), and a fall in blood pressure. Pressure on the common carotid artery below the sinuses reduces the blood pressure within the sinus by reducing the amount of blood flowing into it. This mimics hypotension or decreased blood supply from hemorrhage or shock, causing the heart to beat faster (tachycardia), the blood vessels to constrict (vasoconstriction), and a rise in blood pressure. This explains the fact that, while in most cases of manual strangulation there is bradycardia, vasodilation, and fall in blood pressure, in some cases, if the hands are lower down on the neck, there might instead be tachycardia, vasoconstriction, and a rise in blood pressure.
In normal individuals, pressure on the carotid sinus causes minimal effects with a decrease in heart rate of less than six beats per minute and only a slight reduction in blood pressure (less than 10 mm Hg).28 Some individuals, however, show extreme hypersensitivity to stimulation of the carotid sinuses. In such individuals, there is slowing of the heart and cardiac arrhythmias ranging from ventricular arrhythmias to cardiac stand-still and hypotension. There are cases reported in which turning of the neck in varying positions or a high or tight collar has produced dizziness and fainting.28,29 Some articles refer to cases of stimulation of the carotid sinus that have allegedly produced bradycardia, progressing to cardiac arrest and death.29 Review of the original case reports almost invariably indicates that these individuals were elderly suffering from some severe cardiovascular disease that in itself was capable of causing sudden death.
In manual strangulation, the face usually appears congested and cyanotic, with petechiae of the conjunctivae and sclerae. Di Maio found petechiae present in the conjuctivae or the sclerae in 89% of his cases.26 Fine petechiae might also be present on the skin of the face. The petechiae are most noticeable on the bulbar conjunctivae and conjunctival sac, the skin of the upper and lower eyelids, the bridge of the nose, the brows, and the cheeks. Con-junctival hemorrhages will be larger if the victim struggles and the assailant responds with increased pressure about the neck. The petechiae are caused by rupture of venules and capillaries secondary to increased intravascular pressure as a result of the obstructed venous return (the internal jugular veins) in conjunction with incomplete arterial obstruction, which permits the vertetbral arteries to continue supplying blood to the brain. The characteristic signs of asphyxia — cyanosis, and multiple petechiae — are most striking above the site of manual compression of the neck. Petechiae are not pathognomonic of asphyxial deaths, however. They are also seen in other diseases, for example, acute heart failure. In severe vomiting or coughing, occasional petechiae might be seen. If the body remains in the prone position for a prolonged length of time, such that it is approaching decomposition, postmortem petechiae can form in the distribution of the livor mortis. These petechiae may be present on the skin, conjunctivae and sclerae. On occasion, in cases of manual strangulation, pulmonary edema is present, with foamy edema fluid visible in the nostrils.
In most cases of manual strangulation, the assailant uses more force than is necessary to subdue and kill his victim. Hence, marks of violence are frequently present on the skin of the neck. Typically, there are abrasions, contusions, and fingernail marks on the skin (Figures 8.24, 8.25). Rarely, no marks are present. Dissection of the throat usually reveals hemorrhage, often extensive, into the musculature. Depending on the age of the victim and the amount of force used, there might be fractures of the hyoid bone or thyroid cartilage. As age increases, so does calcification of these structures and the tendency to have fractures. Thus, these fractures are less common in individuals in their teens and late twenties than in individuals over 30 years of age. One must be careful not to mistake the cartilagenous separations between the greater horns of the hyoid and its body and the superior horns of the thyroid cartilage and thyroid plates for fractures. Hemorrhage must always be present at an alleged fracture site before it can be called an antemortem fracture.
The incidence of fractures in manual strangulation is high if a careful dissection of the neck is conducted. In the 41 cases of manual strangulation studied by DiMaio, the incidence of fractures was 68.1% (28 cases) — 100% of the males (14 of 14 cases) and 52% (14 of 27 cases) of the females.26 Harm and Rajs reported an incidence of 70% of their 20 cases; Simpson and Knight 92% of 25 cases.18,30 In DiMaio's cases, of the 14 females with fractures, all
had fractures of the hyoid, either alone (5 cases) or in combination with the thyroid cartilage (4); in combination with the cricoid (3) or in conjunction with both the thyroid and cricoid (2). Of the 14 males, 10 had fractures of the hyoid, either alone (4 cases) or in combination with other structures (6); two had fractures limited to the thyroid cartilage; two to the cricoid cartilage. There were 60 individual fractures in Di Maio's 28 cases. Unilateral fractures
of the hyoid predominated over bilateral fractures 3 to 1. With unilateral fractures of the hyoid, fractures of the left side dominated 11 to 7. All the fractures of the thyroid cartilage involved the superior horns rather than the body of the thyroid. The latter fractures tend to be vertical and are usually caused by a blow to the thyroid cartilage.
Because of its location high up in the neck, the hyoid bone is relatively safe from injury by direct blows unless the neck is arched. In direct blows to the neck, fractures of the hyoid are generally seen only in association with a fracture of the mandible. The U shape of the hyoid does make it susceptible to fracture by compression. Thus, fractures of the hyoid are, as a rule, seen only in strangulation. Whether the fractured ends of the hyoid bone are driven inward or outward is immaterial.
The larynx, lying in front of the fourth through sixth cervical vertebrae, is protected in the midline only by skin and two layers of fascia. It is therefore susceptible to direct neck trauma, i.e., blows to the neck. Thus, fractures of the body of the thyroid cartilage can be seen in blows to the neck. Lateral compression of the larynx, as might be expected in manual strangulation, causes fractures of the cornu (horns) of the thyroid. Fractures of the cricoid cartilage occur most frequently when the cartilage is compressed in an antero-posterior direction against the vertebral column. These fractures, which are usually vertical, might occur in the midline or laterally.
In manual strangulation, there is usually trauma to both the external and internal aspects of the neck. Because of the way the neck is usually grasped, the tips of the four fingers with their associated fingernails dig into the neck.
Depending on the length, sharpness, and regularity of the nails, they can produce linear or semilinear abrasions, scratches, and scrapes (Figure 8.24). The tips of the fingers can produce contusions or erythematous marks. Pressure as applied by the thumb tends not to be at the tip, but on the pad. Therefore, nail marks are less common from the thumb, though a contusion may be present.
Various methods of manual strangulation are used. The simplest involves using one hand and attacking the victim from the front. In this method of attack, one sees small contusions and erythematous marks in association with nail marks on one side of the front of the neck caused by the fingers. An erythematous mark or contusion and, less commonly, a nail mark caused by the thumb, might be present on the opposite side of the neck. If the right hand is used, this thumb mark is on the right side of the neck. If two hands are used and the victim is attacked from the front, there are usually erythema-tous marks and contusions or nail marks on both sides of the front of the neck, usually posterior to the sternocleidomastoid muscles. A variation of a two-handed attack to the front of the neck involves using pressure applied by two thumbs on the central aspect of the neck. Here, the assailant presses both thumbs directly against or along the sides of the larynx and trachea. This results in erythematous markings or contusions of the anterior aspect of the neck. The area of hemorrhage can be either in a bilateral parasagittal plane or confluent across the midline. Fingernail marks, contusions, and erythematous marks caused by the fingers will be on the lateral aspects of the neck.
If either one or two hands are used and the victim is attacked from the back, erythematous marks or contusions from the fingertips, as well as nail marks, are generally found on the front of the neck between the larynx and sternocleidomastoid. With one hand, the marks would be on only one side of the neck; with two hands, on both sides. Bruises from the thumbs will be present on the back of the neck.
A less common method of strangulation is an assault from the front using the palm of the hand to apply pressure to the neck without using the fingertips. The authors have seen this in a number of instances, all of which involved adults who were unconscious through acute alcohol intoxication, or young children. There was no evidence of trauma externally that could be related to either the fingertips or fingernails. In all but one instance, there was congestion of the face and petechiae of the conjunctivae and sclerae, as well as periorbital petechiae of the skin. No hemorrhage was noted internally and there was no injury to the internal structures of the neck.
Nail marks can be classified into three types using the classification of Harm and Rajs: impression marks, claw marks, and scratch marks. Impression marks are "regularly curved, comma-like, exclamation mark-like, dash like, or oval, triangular, rectangular epidermal injuries measuring 10-15 mm in length and up to a few millimeters in breadth." 18 They are produced when the fingertip digs into the skin at a right angle to it with the fingernails penetrating through the epidermis to the dermis. In the case of curved imprints, the concave surface does not necessarily correspond to the concave surface of the nail, but might just as easily be a mirror image.
Claw marks are U-shaped injuries of both the epidermis and dermis, varying in length from 3-4 mm to a few cm. In claw marks, the fingernails dig into the skin at a tangential angle, cutting the epidermis and dermis tangentially and undermining it. Scratch marks are parallel linear abrasions or erythematous bands in the epidermis up to 1.0 cm wide, produced when the fingernails dig into the epidermis at a vertical angle and then are drawn across the skin, producing an elongated injury.
While, in most manual strangulations, there is evidence of both external and internal injury to the neck, in some cases, there is no injury, either externally or internally. One of the authors (VDM), over a period of 3 months, saw three women who had been manually strangled. The first showed absolutely no evidence, either externally or internally; the second showed congestion of the face with fine petechiae of the conjunctivae and skin of the face, but no evidence of injury to the neck, either externally or internally; and the third victim had abrasions and scratches of the skin with extensive hemorrhage into the muscles of the neck. All three women were killed by the same individual. All three had blood alcohols above 0.300 g/dL. The modus operandi of the perpetrator was to meet a woman in a bar, buy her liquor until she was extremely intoxicated, and then go off with her and have sexual intercourse. He would then strangle her. At the time of strangulation, the women were unconscious through acute alcohol intoxication, so a very minimal amount of pressure was necessary. He would place his hand over their necks and push downward, compressing the vessels of the neck. In the last case, the individual regained consciousness and struggled, with the resultant injuries. The perpetrator admitted having killed a number of other women the same way over the past years in a number of states.
In manual strangulation, the victims are usually female. When they are male, they are often highly intoxicated. It is suggested that, in all manual strangulations, a complete toxicological screen be performed.
Sphincter incontinence is thought to be quite characteristic in strangulation. Harm and Rajs addressed this question in a study of 37 dead and 79 surviving victims of strangulation.18 Of the 37 dead victims, 60% (22) had an empty urinary bladder, compared with 14% of 54 control autopsies whose causes of death were other than violence. Of the 79 surviving victims of asphyxia, 5% (4) had sphincter incontinence. Thus, sphincter incontinence, while more common in strangulation, is not an absolute finding.
In cases of strangulation, the presence of fractures of the larynx or hyoid indicate only that pressure or force has been applied to the neck. These fractures by themselves do not cause death. They are just markers of neck trauma. The authors have seen cases where someone has attempted to strangle an individual, causing fractures of the thyroid cartilage or hyoid, only to give up and stab or beat the victim to death.
One must be sure that the fractures are antemortem, because it is not uncommon to fracture the larynx at the time of autopsy. The distinguishing characteristic of an antemortem fracture is hemorrhage at the fracture site. This hemorrhage should be grossly visible. Hemorrhage demonstrable only microscopically can be a postmortem artifact. In handling suspected strangulation cases, one must be very careful about the interpretation of retro-esophageal and paravertebral cervical hemorrhage. Bleeding over the front and sides of the larynx is virtually always diagnostic of trauma e.g., strangulation, a blow, or an intravenous line. This is not the case for retro-esophageal and paravertebral cervical hemorrhage. These are almost always an artifact and are often seen in natural deaths, especially in elderly individuals dying slowly, i.e., hypoxic deaths.2,31 The presence of petechiae of the mucosa of the epiglottis or larynx is not diagnostic of strangulation or any specific form of asphyxia.
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