Determination of the time of death is important in both criminal and civil cases. In criminal cases, it can set the time of the murder, eliminate or suggest suspects, confirm or disprove an alibi. In civil cases, the time of death might determine who inherits property or whether an insurance policy was in force. Unfortunately, all methods now in use to determine the time of death are to a degree unreliable and inaccurate. They usually give vague or dubious answers. The longer the postmortem interval, i.e., the time between death and the attempt to determine time of death, the less precise the estimate of the interval. One obvious facet of time of death determination often not considered is that the time the fatal injury is incurred is not necessarily the time of death. One can incur massive fatal injuries, yet linger in an unconscious state for hours prior to death (Figure 2.1). Many factors are or have been used in determining the time of death:
Scene markers (papers, letters, clothing, televisions, TV schedules, etc.) Livor Mortis
Livor mortis (lividity, postmortem hypostasis) is a reddish purple coloration in dependent areas of the body due to accumulation of blood in the small vessels of the dependent areas secondary to gravity (Figure 2.2A). Postmortem lividity is occasionally misinterpreted as bruising by people unfamiliar with this phenomenon.
Dependent areas resting against a firm surface will appear pale in contrast to the surrounding livor mortis due to compression of the vessels in this area, which prevents the accumulation of blood. Thus, areas supporting the weight of the body, for example, the shoulder blades, buttocks,
and calves in individuals lying on their backs, show no livor mortis, but appear as pale or blanched areas (Figure 2.2B, C). Tight clothing, for example, a brassiere, corset, or belt, which compresses soft tissues, collapsing the vessels, also produces pale areas.
Livor mortis usually, but not invariably, has a cherry-red to pinkish color in deaths due to carbon monoxide. This is due to carboxyhemoglobin. Identical coloration may be caused by exposure of a body to cold temperatures, and in deaths due to cyanide.Localized areas of bright red livor mortis are
also seen adjacent to chest tubes. In all three of the aforementioned entities, the coloration is caused by predominance of oxygenated hemoglobin.
Livor mortis is usually evident within 30 min to 2 h after death. In individuals dying a slow lingering death with terminal cardiac failure, livor mortis may actually appear antemortem. Livor mortis develops gradually, usually reaching its maximum coloration at 8-12 h. At about this time, it is said to become "fixed." Prior to becoming fixed, livor mortis will shift as the body is moved. Thus, if an individual dies lying on his back, livor mortis develops posteriorly, i.e., on the back. If one turns the body on its face, blood will drain to the anterior surface of the body, now the dependent aspect. Livor mortis becomes "fixed" when shifting or drainage of blood no longer occurs, or when blood leaks out of the vessels into the surrounding soft tissue due to hemolysis and breakdown of the vessels. Fixation can occur before 8-12 h if decomposition is accelerated, or at 24-36 h if delayed by cool temperatures. Thus, the statement that livor mortis becomes fixed at 8-12 h is really just a vague generalization. That livor mortis is not fixed can be demonstrated by applying pressure to a dependent discolored area and noting the subsequent blanching at the point of pressure.
Although livor mortis may be confused with bruising, bruising is rarely confused with livor mortis. Application of pressure to an area of bruising will not cause blanching. An incision into an area of contusion or bruising shows diffuse hemorrhage into the soft tissue. In contrast, an incision into an area of livor mortis reveals the blood to be confined to vessels, without blood in the soft tissue.
Livor mortis also occurs internally, with settling of the blood in the dependent aspects of an organ. This is most obvious in the lungs.
As the blood accumulates in the dependent areas, the pressure of the settling blood can rupture small vessels, with development of petechiae (minute hemorrhages or Tardieu spots) and purpura (patches of purplish discoloration) (Figure 2.3). This usually takes 18-24 h and often indicates that decomposition is fast approaching. This phenomenon is more common in asphyxial or slow deaths. Unfortunately, as time passes, it cannot always be determined with certainty whether the purpura produced are ante- or postmortem. Presence of petechiae and purpura only in dependent areas suggests a postmortem origin. In limbs hanging over the side of a bed or the legs and forearms of an individual who is hanging, Tardieu spots may develop even more rapidly, appearing as early as 2-4 h after death.
Livor mortis can cause difficulty in interpreting head injuries in decomposed bodies. In a body lying on its back, blood accumulates in the posterior or dependent half of the scalp due to gravity. In advanced decomposition, with lysis of red blood cells and breakdown of the vessels, there is seepage of blood into the soft tissue of the scalp. This gives the appearance of confluent bruising and cannot always be differentiated from true antemortem bruising. There will, of course, be no abrasion or laceration of the scalp, but all forensic pathologists have seen extensive scalp contusions without abrasions or lacerations. In decomposed bodies, blood collecting in the occipital areas of the brain due to gravity may escape through small vessels, producing very thin localized films of blood in the subarachnoid or subdural spaces coating the occipital lobes. The rest of the brain does not show subarachnoid or subdural hemorrhage. In drownings where the body floats head down, decomposition produces the picture of
diffuse scalp hemorrhage. Rarely, postmortem leakage of blood into the soft tissue and muscle of the anterior aspect of the neck may also occur in drownings. This "bleeding" is minimal.
Livor mortis is not very important in determining the time of death. It is important, however, in determining whether the body has been moved.
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