Asphyxia by smothering is caused by the mechanical obstruction or occlusion of the external airways, i.e., the nose and mouth. Deaths such as these are usually either homicide or suicide, very rarely accident (Figure 8.1).
The most common form of suicidal smothering is the placing of a plastic bag over an individual's head (Figure 8.1 A). If it is heavy plastic, it may be secured at the neck. More commonly, suicides employ the thin, filmy plastic bag used by dry cleaners. Here, there is often no necessity to secure the bag at the neck, because it clings to the face, occluding the airways. These filmy plastic bags also account for the rare accidental deaths by smothering when these bags are used to cover a mattress or pillow in a crib of a young child. The child becomes enmeshed in the bag and smothers. In all the deaths that the authors have seen in which plastic bags have been placed over the head, there have been no specific autopsy findings. Petechiae of the face, sclerae, and conjunctivae were virtually always absent. Petechiae of the epicardium or pleural surfaces of the lung were sometimes present, but these are so nonspecific that the authors do not give any weight to them. If an individual commits suicide by use of a plastic bag and the bag is removed prior to notification of the authorities, a medical examiner cannot determine the cause of death by the autopsy.
There are occasional allegations of infants smothering in their cribs because of heavy blankets or bedding placed over them. The authors feel that these cases are examples of sudden infant death syndrome (SIDS) and that it is just coincidental that they are found covered by bed clothes. One can pile a number of blankets on an infant without causing any respiratory difficulty.
Occasionally, an alcoholic is found face down on a pillow, dead. Circumferential oral and nasal pallor is noted and death is attributed to smothering. This pallor, however, can be caused post mortem by passive pressure of the dependent head on the pillow. Thus, the diagnosis cannot be made on this "evidence." The authors have grave reservations about this diagnosis. An individual would have to be in an alcoholic coma to smother this way. Alcoholic coma, however, puts them in grave danger of death anyway and this is more likely the cause of death, rather than the alleged suffocation.
Accidental smotherings can occur with defective cribs. Here, an infant is trapped either between a too-small mattress and the frame of the crib, or between a defective crib and mattress, with the face wedged against the mattress (Figure 8.2). The child is unable to move and smothers.
Gags obstructing the nose and mouth can cause death by smothering. Such deaths, though unintentional, are still homicides if the victims die during the commission of a crime. Typically, a gag is placed around the face obstructing the mouth and nose (Figure 8.3). Victims are usually elderly individuals who are either unable to struggle sufficiently to move the gag or who are unusually susceptible to the anoxia by virtue of natural disease. Mucus and fluids may accumulate in the nasal cavities and airways, contributing to asphyxia. In the elderly, there may be congestion of the face with
scattered fine petechiae of the sclerae, conjunctivae, and skin of the face. This has not been the case in young individuals in whom petechiae are usually absent. It is the discovery of the gag obstructing the airways that makes the diagnosis, not alleged signs of asphyxia.
In homicide by smothering, the implements used are usually pillows, bedding, and the hands. Infants may be placed in plastic bags. The victims tend to be very young, very old, debilitated, or incapacitated by restraints, disease or drugs. It is extremely difficult to smother adults in full control of their faculties.
When a pillow is used, it is placed over the face and pushed down. This causes obstruction of the nose and mouth, asphyxia, and death. There are usually no marks on the face. The face is not congested and there are no petechiae of the sclerae or conjunctivae (Figure 8.4). Abrasion injuries of the face will occur only if the victim puts up a vigorous resistance. In a review of 15 smothering deaths involving children below the age of 2 years, of the 13 who could be evaluated for the presence of petechiae, only one had findings. This child had a single petechia of the conjunctiva and a single area of scleral hemorrhage. Because of the circumstances of this case, there was the possibility that the child might also have been choked. Pushing the face into the bedding will accomplish the same end as using a pillow.
Smothering can also be accomplished using the hands. The nose is pinched off with one hand, while the other hand is used to push the jaw closed. In small children, one hand can accomplish both these tasks. In infants and adults unable to put up any effective resistance, an autopsy will fail to disclose any injury due to this process. In adults, even those who can muster only a minimal struggle, there may be abrasions on the nose or chin from the fingernails, and contusions of the lips from pressure of the palm (Figure 8.5).
The sequence of physiological events in smothering is:
• Bradycardia (decrease in heart rate)
• Decrease in respiration to agonal gasps with eventual cessation of respiration
• Slowing and finally flattening of the electroencephalogram (EEG)
The heart will continue to beat even after flattening of the EEG. In infants, bradycardia has been observed to start 30 sec after the initiation of smothering, and flattening of the EEG at 90 sec.6 If, after cessation of respiration, the pillow or hand is removed from the face, respiration will not usually restart spontaneously. The individual must be resuscitated. Violent struggles with increased utilization of oxygen can speed up this sequence of events, just as natural disease could make the individual more susceptible to the effects of hypoxia.
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