The combined examination of bloodstains on the victim, assailant, weapon, and scene should be a routine procedure in all cases. For the forensic pathol- ogist there are additional parameters and factors that should be considered in conjunction with blood at the scene which involve the amount or volume of blood that has been shed. There is also a need to relate the quantity of blood with the nature of the bleeding and the anatomic site of bleeding. This may be especially helpful in those cases where the victim has been injured or killed at the scene and removed to another location.
Examination of the blood at the scene may also be used as a source of information as to the survivability of the victim after injury. The careful examination of the blood accumulation may reveal additional tissue such as hair, skin, and brain tissue whose presence would help establish not only the injury site on the victim but also the capabilities of the victim after injury and an approximation of post-injury survival time. The appearance of the blood may also provide information regarding the origin of blood from the body. Lung injuries often result in frothy blood in the mouth associated with respirations of the victim. There may be evidence of the coughing up or vomiting of blood that would be significant. A cut to the sides of the neck may result in the severance of the carotid artery and produce a rapid spurting type of bleeding and rapid disability of the victim with death occurring very shortly after the injury at the location where the attack took place. This would also apply to accidental or suicidal injuries to areas of the body where arteries are accessible.
Abdominal or chest wounds very often have little or no extrusion of blood since blood may accumulate within the body cavities. The clothing may become soaked and impede further extrusion of blood from the body.
Clothing which is tight against the skin of a victim may impede the outward flow of blood from the body. A prone or supine body may have blood leakage owing to gravity depending upon the position of the body. A chest wound on a victim who is on his back may show little evidence of external bleeding but when the body is turned over considerable blood may leak from the chest cavity. If the circulation is impaired by the rapid drop of blood pressure prior to death, external blood loss may be minimal. Cold temperatures may limit the extent of bleeding in a victim because of the body’s reaction to preserve internal heat by peripheral vessel contraction.
The determination of the period of time that the blood has been present on a surface may be an issue as well. This may relate to the clotting time of blood as well as the drying time of quantities of blood on a particular surface and may have to be determined by experimental work as discussed in Chapter 4. The character of the blood at the scene must be described as to the degree of drying and clotting. The blood clots will change after a period of time with visible separation of the serum from the clot. It may be possible to relate the appearance of the blood clot and drying of blood to its approximate time of deposition. Although it is variable, one might expect a considerable amount of dried blood at a scene 24 hours after injury. The environment and type of surface upon which the blood is deposited are important consider- ations with experiments of this type.
Attempts to evaluate cases in which blood loss evidence is a crucial factor have to be based on the fact that the known volume of blood present in a normal person is in the range of 5000 to 6000 ml or 5 to 6 liters (Figure 5.15). When the vascular system of a victim is disrupted so that the blood is able to leak or leave the vessels, the stability of the body will change. Blood may leave the circulatory system externally or accumulate within the cranial, thoracic, pericardial, or peritoneal cavities. When 20 to 25% of the blood volume is lost from the circulation (1000 to 1500 ml), the first symptoms of shock are imminent. This is significant when one also considers this change in conjunction with injuries to a specific organ such as the heart, lungs, or brain whose dysfunction will produce additional changes to impair the victim. The rate of bleeding is also a factor that will vary according to the portion of the vascular system that is injured.
The degree of intoxication involving alcohol and/or drug use may have an indirect effect on the amount of bloodshed. After injury, the activities of intoxicated victims may be related to their reduced sense of inhibition and unusual behavior, and increased physical activity may increase bleeding because of the increased action of the heart. Persons may exhibit aggressive behavior which may include attacks on others producing additional injuries, jumping from heights, or attempting to break away from law enforcement officers there to assist them.
The volume of blood loss becomes important for several reasons includ- ing the evaluation of the degree of activity of a victim after he or she has received a lethal injury. Estimations of external blood volume should be made at the scene as well as internally during the postmortem examination by measuring the volume of free blood present in the various body cavities. The rapidity of death after the wound has been sustained is an important factor to evaluate plus the possibility that the assailant’s clothing received victim’s blood during the struggle or attack.
The various situations where blood evidence becomes important do not always involve criminal cases as in the case of the accidental leakage of blood from a surgical patient when intravenous tubing became disconnected and significant blood loss occurred. The questions were how to measure the blood loss in a quantitative manner and to evaluate the significance of the blood loss in relation to the death of the patient. Unexpected internal bleeding may bring up questions as to cause and what measures of medical treatment would have been effective under the proper conditions. The question of activity after a lethal injury is frequently asked during testimony in trials. The degree of external and internal bleeding must be carefully evaluated in these cases.
Figure 5.15 The average quantity of blood in the human body represented as units of blood is approximately 5000 to 6000 ml or 5 to 6 liters.