Carbon Monoxide Poisoning - How Is Death Determined From An Arson Crime Scene?

When CSI investigators arrive at a crime scene such as arson and find a dead body, the first thing they want to know is how the person died assuming that the body is not burned beyond recognition. They will look for cuts, bruises, gunshot wounds, knife wounds, or evidence of strangulation to make that determination since the person may not necessarily have died from smoke inhalation. However, not all of this evidence may be apparent to the naked eye for a CSI technician. A highly trained medical examiner may have to take a closer look at the body to arrive at a more educated guess as to how the person passed. For that reason, the body is shipped off to a medical examiner's office for autopsy.

In this article, we will elaborate on one of the possible causes of death called asphyxiation. We will also explain how a medical examiner makes this determination by analyzing the blood and tissues of the deceased.

Asphyxiation, aka suffocation, from the breathing in of air deficient in oxygen can contribute to a death. A medical examiner (ME) can run tests on the victim's blood and tissues to determine what substances, if any, are present. If, for example, the victim's blood shows a presence of carbon monoxide (CO) between 45 and 90 percent, this will lead the ME to arrive at a conclusion that the victim died of CO asphyxiation. Finding levels of CO this high in a victim suggests that he/she died from smoke and CO inhalation. However, low levels of CO may indicate that the victim died just prior to a fire being set.

Interpreting the CO level is also dependent upon the evaluation of the pathology in the deceased individual. An elderly person with severe coronary artery disease will die from a lower level of CO than a young individual with a healthy body.

Carbon monoxide intoxication (greater than normal levels of CO in the bloodstream) not only contributes to death, many times it prevents victims from escaping before the fire kills them. As the CO level in the bloodstream goes up, the person loses the capability to think and move properly. At a 20 percent CO level in the bloodstream, the person experiences dizziness and confusion. At a 35 percent CO level in the bloodstream, the person undergoes muscular weakness, loss of coordination, and disorientation. At levels greater than 50 percent, the victim loses consciousness and dies. Even if the victim is alive and has ample time to escape when a fire starts, the toxicity level of CO may prevent him/her from doing so.

During an autopsy, victims of CO intoxication display several characteristics. One of these is unique coloring. As you breath in CO, it hooks up with another molecule called hemoglobin, the iron-containing pigment of red blood cells, to make a compound called carboxyhemoglobin, which is bright red in color. If the victim's blood, organs, and muscles, are bright red or cherry-like in color, the victim most likely died from smoke and CO inhalation. However, definitive proof can be made by conducting a scientific analysis of the CO levels in the blood and tissues.

Other than evidence of increased blood CO level, soot in the mouth, throat, lungs, and airways suggests that the person was alive as the fire spread. On the other hand, if the CO level is low and there was no soot found in the airways, the ME can consider other causes and manners of death. One possibility that could be considered is homicide.

What if CSI technicians found a body that was tied up, gagged, and shot? The ME conducts blood CO levels to ascertain the cause of death. Did the shooting or the fire kill the victim? If the ME found high blood CO levels and soot in the airways and lungs, he could conclude that the victim was alive after a gunshot and subsequently died as a result of CO inhalation caused from the fire. If low blood CO levels were found, the gunshot is more likely the cause of death. This finding can be crucial to the prosecuting attorneys if there was more than one perpetrator in a crime. One person pulled the trigger, while the other started the fire. One is considered the murderer while the other is an accomplice.

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