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Authors: John H. Trestrail
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allows the poisoner to lessen the guilt that he or she may feel about being the one who actively carries out the deed ( see Fig. 2-4 ).
2.4. HOW DO POISONS KILL?
Like a wrench thrown into a finely tuned engine of a car would disrupt its proper running, the chemical molecule, like a “chemical monkey wrench,”
disrupts the proper running of the body’s biochemical processes. Literally thousands of these “chemical monkey wrenches” are available to the poisoner. Each poison can be carefully selected to disrupt a specific body process. Fig. 2-5 shows some of the major classifications of poisons based on how they will do their dirty work on various organ systems.
Poisons can kill a victim in a number of ways, depending on the effects of the chemical substance on the body’s normal physiology.
2.4.1. Central Nervous System Effects
By altering the critical function of the body’s nervous system, a poison can cause central nervous system depression, resulting in coma; loss of the respiratory drive, resulting in respiratory arrest (the stoppage of breathing); and loss of the reflexes protecting the airway, resulting in a flaccid tongue obstructing the airway, or aspiration of gastric contents into the bronchial tree. The poison can also affect the heart with cardiovascular (circulatory) effects, including hypotension (low blood pressure) from decreased cardiac contractions, hypovolemia from loss of fluids, peripheral vascular collapse, or cardiac arrhythmias.
The body’s cells can die from a lack of oxygen necessary for normal cellular respirations, called cellular hypoxia (low oxygen at the cellular level), owing to a breakdown in the normal transport of oxygen. There can be seizures resulting from muscle hyperactivity, which results in hyperpyrexia (increase in body temperature); or kidney failure, resulting from destruction of muscle tissue (deposition of myoglobin in the kidneys). There can be brain
36
Criminal Poisoning
Figure 2-4
damage from lack of oxygen, which results in loss of the master control for the entire body engine. Death can be caused by pulmonary aspiration, which results in chemically induced pneumonia and destruction of the lungs.
Some poisons seem to pinpoint specifically a particular vital organ of the body. For example, the herbicide Paraquat destroys the lungs, the analgesic acetaminophen or the fungal amatoxins destroy the liver, and antifreeze (ethylene glycol) or another fungal toxin called orellanine destroys the kidneys.
For some of the more common homicidal poisons, the investigating officer and analytical toxicologist can find poison profiles in the appendix to this
Types of Poisons
37
Figure 2-5
volume. In each profile, the investigator will find discussions of the following important points about the poison: • Form
• Common color
• Characteristic odors
• Solubility
• Taste
• Common sources
• Lethal dose
• Mechanism
• Possible methods of administration
• Time interval of onset of symptoms
• Symptoms resulting from acute exposure
• Symptoms resulting from chronic exposure
• Disease states mimicked by poisoning
• Notes relating to the victim
• Specimens from the victim to be obtained for analysis
• Analytical detection methods
• Known toxic levels
• Notes pertinent to analysis of the poison
• List of selected homicide cases in which particular poisons were used What quantity of a poison would be necessary to produce a lethal outcome in a human victim? Many individuals are surprised to learn that a minute amount of a poison can result in death. To give the reader a hands-on feel for lethal amounts, let us use as a reference the weight of one US nickel (or two
38
Criminal Poisoning
Figure 2-6
pennies). The average weight of these American coins is approx 5000 mg. If one had the same weight of some common homicidal poison, how many human lethal doses would this weight equal? See Fig. 2-6 for examples of poisons and the
2.4. HOW DO POISONS KILL?
Like a wrench thrown into a finely tuned engine of a car would disrupt its proper running, the chemical molecule, like a “chemical monkey wrench,”
disrupts the proper running of the body’s biochemical processes. Literally thousands of these “chemical monkey wrenches” are available to the poisoner. Each poison can be carefully selected to disrupt a specific body process. Fig. 2-5 shows some of the major classifications of poisons based on how they will do their dirty work on various organ systems.
Poisons can kill a victim in a number of ways, depending on the effects of the chemical substance on the body’s normal physiology.
2.4.1. Central Nervous System Effects
By altering the critical function of the body’s nervous system, a poison can cause central nervous system depression, resulting in coma; loss of the respiratory drive, resulting in respiratory arrest (the stoppage of breathing); and loss of the reflexes protecting the airway, resulting in a flaccid tongue obstructing the airway, or aspiration of gastric contents into the bronchial tree. The poison can also affect the heart with cardiovascular (circulatory) effects, including hypotension (low blood pressure) from decreased cardiac contractions, hypovolemia from loss of fluids, peripheral vascular collapse, or cardiac arrhythmias.
The body’s cells can die from a lack of oxygen necessary for normal cellular respirations, called cellular hypoxia (low oxygen at the cellular level), owing to a breakdown in the normal transport of oxygen. There can be seizures resulting from muscle hyperactivity, which results in hyperpyrexia (increase in body temperature); or kidney failure, resulting from destruction of muscle tissue (deposition of myoglobin in the kidneys). There can be brain
36
Criminal Poisoning
Figure 2-4
damage from lack of oxygen, which results in loss of the master control for the entire body engine. Death can be caused by pulmonary aspiration, which results in chemically induced pneumonia and destruction of the lungs.
Some poisons seem to pinpoint specifically a particular vital organ of the body. For example, the herbicide Paraquat destroys the lungs, the analgesic acetaminophen or the fungal amatoxins destroy the liver, and antifreeze (ethylene glycol) or another fungal toxin called orellanine destroys the kidneys.
For some of the more common homicidal poisons, the investigating officer and analytical toxicologist can find poison profiles in the appendix to this
Types of Poisons
37
Figure 2-5
volume. In each profile, the investigator will find discussions of the following important points about the poison: • Form
• Common color
• Characteristic odors
• Solubility
• Taste
• Common sources
• Lethal dose
• Mechanism
• Possible methods of administration
• Time interval of onset of symptoms
• Symptoms resulting from acute exposure
• Symptoms resulting from chronic exposure
• Disease states mimicked by poisoning
• Notes relating to the victim
• Specimens from the victim to be obtained for analysis
• Analytical detection methods
• Known toxic levels
• Notes pertinent to analysis of the poison
• List of selected homicide cases in which particular poisons were used What quantity of a poison would be necessary to produce a lethal outcome in a human victim? Many individuals are surprised to learn that a minute amount of a poison can result in death. To give the reader a hands-on feel for lethal amounts, let us use as a reference the weight of one US nickel (or two
38
Criminal Poisoning
Figure 2-6
pennies). The average weight of these American coins is approx 5000 mg. If one had the same weight of some common homicidal poison, how many human lethal doses would this weight equal? See Fig. 2-6 for examples of poisons and the
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