Deaths occurring while an individual is being restrained are extremely rare. In the UK Police Research Group Paper (26), which covers the period
1990-1996, 16 cases are identified where police action "may have been associated with the death" amounting to 6% of the deaths that this group studied. From consideration of the medical aspects of these deaths recorded in their report, it would appear that six of the deaths resulted from natural disease and four were related to drug use or abuse. Of the remaining six cases, one was associated with a baton blow to the head, two to asphyxiation resulting from pressure to the neck, two to "restraint asphyxia," and one to a head injury. Therefore, in the deaths during the 7 years that this group considered, a total of four deaths (<1.5% of the 267 deaths in police custody reviewed by this group) were apparently directly associated with asphyxia during restraint.
However, the close association of these deaths with the actions of the police in restraining the individual raises questions about the pathologists' conclusions and their acceptance by the courts. It is common for several pathological opinions to be obtained in these cases; in a review of 12 in-custody deaths, an average of three opinions had been obtained (range 1-7) (27). Indeed, in one of the cases cited as being associated with police actions, seven pathological opinions were sought, yet only one opinion is quoted. This points to the considerable difficulty in determining the relative significance of several different and, at times, conflicting areas of medical evidence that are commonly present in these cases.
The area of restraint that causes the most concern relates to asphyxiation during restraint. It has been known in forensic circles for many years that individuals may asphyxiate if their ability to breathe is reduced by the position in which they are placed or into which they fall (Subheading 7.1.; ref. 28). This type of asphyxiation is commonly associated with alcohol or drug intoxication or, rarely, with neurological diseases that prevent the individual from extracting themselves from a position that either partially or completely occludes their mouth and nose or limits the freedom of movement of the chest wall. Death resulting from these events has been described as postural asphyxia to indicate that it was the posture of the individual that resulted in the airway obstruction rather than the action of a third party.
In 1988, research by Reay et al. (29) was published that was initially believed to show that in laboratory conditions, placing an individual in the hog-tie position significantly increased the time taken to return to resting blood oxygenation levels after moderate exercise. "Hog-tieing" is a form of restraint where the detainee is placed face down and the hands are tied together and then tied to the feet. Reay concluded that positional restraint (hog-tieing) had "measurable physiological effects." In 1992, Reay published an article (30) that recorded six cases where, in his opinion, individuals had died as a result of "hog-tieing" and being placed prone in police vehicles. This article raised the possibility that asphyxiation was occurring to individuals when they could not move themselves to safer positions because of the type of restraint used by the police. The concept of "restraint asphyxia," albeit in a specific set of circumstances, was born.
Since the description of deaths in the prone hog-tied position, Reay's original concepts have been extended to account for many deaths of individuals simply under restraint but not in the hog-tied position. The term restraint asphyxia has been widened to account for these sudden and unexpected deaths during restraint. Considerable pathological and physiological controversy exists regarding the exact effects of the prone position and hog-tieing in the normal effects upon respiration. Further experiments by Chan et al. (31) have cast considerable doubt on Reay's thesis, although other experiments by Roeggla et al. (32) support the original theory. Although the physiological controversy continues, it is clear to all those involved in the examination and investigation of these deaths that there is a small group of individuals who die suddenly and apparently without warning while being restrained.
Recent physiological research on simulated restraint (33,34) revealed that restraint did produce reductions in the ventilatory capacity of the experimental subjects but that this did not impair cardiorespiratory function. In two of the eight healthy subjects, breath holding after even moderate exercise induced hypoxia-related dysrhythmias, and it was noted that arterial oxygen saturation fell rapidly even with short breath hold times, especially if lung volume was reduced during exhalation.
The problem that currently faces the forensic pathologist is the determination of the cause or causes of these deaths. This is made harder because there are seldom any of the usual asphyxial signs to assist and, even if those signs are present, it is difficult to assign weight or significance to them because similar changes can be caused simply by resuscitation (35,36).
The major features of asphyxiation are cyanosis, congestion, and petechial hemorrhages (14). These features are seen to a greater or lesser extent in many, but not all, cases of asphyxiation. They often are completely absent in many plastic bag asphyxiations and in hanging, they have variable presence in manual strangulation, and they are most commonly seen in ligature strangulation. However, their most florid appearances are in deaths associated with postural asphyxia or crush asphyxia cases where death has occurred slowly and where it is associated with some form of pressure or force reducing the ability of the individual to maintain adequate respiratory movement, either from outside the body or from the abdominal contents splinting the diaphragm.
It is of interest then that these features, if present at all in these cases are, at most, scant and do not reflect their appearance in other cases of crush asphyxia, suggesting that different mechanisms are the cause of death in these two sets of circumstance.
The individuals who die during restraint are not infrequently under the influence of drugs (particularly cocaine) or alcohol; they may be suffering from some underlying natural disease (particularly of the cardiovascular system), or they may have suffered some trauma. These "additional" factors are sometimes seized by pathologists and courts to "explain" the death, sometimes even in the face of expert opinion that excludes the additional factor from playing a major part in the death. It would seem that there is a subgroup of the population that is either permanently or temporarily susceptible to the effects of restraint, whether those effects be mediated entirely or partially through decreased respiratory effort or some other factor.
There is a separate entity, the exact cause of which is not yet clear, where otherwise fit and healthy individuals die suddenly while being restrained and yet do not show significant features of asphyxiation. It is hoped that further research on the physiology of restraint will elucidate the mechanisms that cause death in these cases. Until these mechanisms are established, it is reasonable to propose that these deaths should be classified for what they are—rapid unexplained death during restraint—rather than to conclude that the cause of death cannot be determined or to ascribe a doubtful medical or toxicological cause of death that does not bear close scrutiny.
Deaths classified as rapid unexplained death during restraint must fulfill several of the following criteria:
1. The death must have occurred during restraint, and the individual must have collapsed suddenly and without warning.
2. A full external and internal postmortem examination must have been performed by a forensic pathologist, which did not reveal macroscopic evidence of significant natural disease, and subsequently a full histological examination of the tissues must have been performed, which did not reveal microscopic evidence of significant natural disease.
3. Studies must not reveal genetic markers of significant disease.
4. There must be no evidence of significant trauma or of the triad of asphyxial signs.
5. A full toxicological screen must have been performed that did not reveal evidence of drugs or alcohol that, alone or in combination, could have caused death.
The small numbers of these deaths in any single country or worldwide makes their analysis difficult; indeed, to search for a single answer that will explain all of these deaths may be futile. The bringing together of these deaths under a single classification would make the identification of cases and their analysis easier.
The problem for the police is that when approaching and restraining an individual, they cannot know the background or the medical history nor can they have any idea of the particular (or peculiar) physiological responses of that individual. The techniques that are designed for restraint and the care of the individual after restraint must allow for safe restraint of the most vulnerable sections of the community.
New research into the effects of restraint may possibly lead to a greater understanding of the deleterious effects of restraint and the development of safer restraint techniques. Although this experimental work is being performed, the only particular advice that can be offered to police officers is that the prone position should be maintained for the minimum amount of time only, no pressure should be applied to the back or the chest of a person restrained on the floor, and the individual should be placed in a kneeling, sitting, or standing position to allow for normal respiration as soon as practical.
It should be noted that an individual who is suffering from early or late asphyxiation may well struggle more in an attempt to breathe, and, during a restraint, this increased level of struggling may be perceived by police officers as a renewed attempt to escape, resulting in further restriction of movement and subsequent exacerbation of the asphyxial process. Officers must be taught that once restrained, these further episodes of struggling may signify imminent asphyxiation and not continued attempts to escape, that they may represent a struggle to survive, and that the police must be aware of this and respond with that in mind.
Since these matters were first brought to forensic and then public attention and training and advice to police officers concerning the potential dangers of face down or prone restraints, especially if associated with any pressure to the chest or back improved, there has been a decrease in the number of deaths during restraint. However, even one death in these circumstances is too many, and it is hoped that by medical research, improved police training, and increased awareness of the dangers of restraint that these tragic deaths can be prevented.
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