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Chapter 8
Toxicology: Poisons and Alcohol
2Kendall/Hunt Publishing Company 2
Lesson Essential Questions:
1. What is toxicology?
2. How is toxicology important in forensic science?
3. What are the ways that scientists measure drugs, alcohol, and poisons?
Chapter 8
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Toxicology
Toxicology—the study of the adverse effects of chemicals or physical agents on living organisms
Types:Environmental—air, water, soil
Consumer—foods, cosmetics, drugs
Medical, clinical, forensic
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Forensic Toxicology
Postmortem—medical examiner
or coroner
Criminal—motor vehicle accidents (MVA)
Workplace—drug testing
Sports—human and animal
Environment—industrial, catastrophic, terrorism
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Toxicology
Toxic substances may:
Be a cause of death
Contribute to death
Cause impairment
Explain behavior
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Historical Perspective of Poisoners
Olympias—a famous Greek poisoner
Locusta—personal poisoner of Emperor Nero
Lucretia Borgia—father was Pope Alexander VI
Madame Giulia Toffana—committed over 600 successful poisonings, including two popes
Hieronyma Spara—formed a society to teach women how to murder their husbands
Madame de Brinvilliers and Catherine Deshayes—French poisoners
AND many others through modern times.
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The Severity of the Problem
“If all those buried in our cemeteries who were poisoned could raise their hands, we would probably be shocked by the numbers.”
—John Harris Trestrail, Criminal Poisoning
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People of Historical Significance
Mathieu Orfila—known as the father of forensic toxicology, published in 1814 Traité des poisons which described the first systematic approach to the study of the chemistry and physiological nature of poisons
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Aspects of Toxicity
Dosage The chemical or physical form of the substance The mode of entry into the body Body weight and physiological conditions of the victim, including
age and sex The time period of exposure The presence of other chemicals in the body or in the dose
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Lethal Dose
LD50 refers to the dose of a substance that kills half the test population, usually within four hours
Expressed in milligrams of substance per kilogram of body weight
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Toxicity Classification
LD50 (rat,oral) Correlation to Ingestion by 150-lb Adult Human
Toxicity
<1 mg/kg a taste to a drop extreme
1–50 mg/kg to a teaspoon high
50–500 mg/kg to an ounce moderate
500–5,000 mg/kg to a pint slight
5–15 g/kg to a quart practically nontoxic
Over 15 g/kg more than 1 quart relatively harmless
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Toxicology: Poisons and Alcohol
12Kendall/Hunt Publishing Company 12
Symptoms of Various Types of Poisoning
Symptom/EvidenceCharacteristic burns around the lips and
mouth of victim
Red or pink patches on the chest and
thigh, unusually bright red lividity
Black vomit
Greenish-brown vomit
Yellow vomit
Coffee-brown vomit, onion or garlic odor
Burnt almond odor
Extreme diarrhea
Nausea and vomiting, unconsciousnesspossibly blindness
Type of PoisonCaustic poison (lye)
Carbon monoxide
Sulfuric acid
Hydrochloric acid
Nitric acid
Phosphorus
Cyanide
Arsenic, mercury
Methyl (wood) or isopropyl
(rubbing) alcohol
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Critical Information
FormCommon colorCharacteristic odorSolubilityTasteCommon sourcesLethal doseMechanismPossible methods of
administrationTime interval of onset of
symptoms
Symptoms resulting from an acute exposure
Symptoms resulting from chronic exposure
Disease states mimicked by poisoningNotes relating to the victimSpecimens from victimAnalytical detection methodsKnown toxic levelsNotes pertinent to analysis of poisonList of cases in which poison was used
—John Trestrail from Criminal Poisoning
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To Prove a Case
Prove a crime was committed
Motive
Intent
Access to poison
Access to victim
Death was homicidal
Death was caused by poison
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Forensic Autopsy
Look for:
• Irritated tissues
• Characteristic odors
• Mees lines—single transverse white bands on nails
Order toxicological screens
• Postmortem concentrations should be done at the scene for comparison.
• No realistic calculation of dose can be made from a single measurement.
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Human Specimens for Analysis
Blood
Urine
Vitreous humor of eyes
Bile
Gastric contents
Liver tissue
Brain tissue
Kidney tissue
Hair/nails
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Alcohol—Ethyl Alcohol (C2H5OH)
Most abused drug in America
About 40 percent of all traffic deaths are alcohol-related
Toxic—affecting the central nervous system, especially the brain
Colorless liquid, generally diluted in water
Acts as a depressant
Alcohol appears in blood within minutes of consumption; 30–90 minutes for full absorption
Detoxification—about 90 percent in the liver
About 5 percent is excreted unchanged in breath, perspiration, and urine
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Rate of Absorption
Depends on:
Amount of alcohol consumed
The alcohol content ofthe beverage
Time taken to consume it
Quantity and type of food present in the stomach
Physiology of the consumer
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BAC: Blood Alcohol Content
Expressed as percent weight per
volume of blood
Legal limit in all states is 0.08
percent
Parameters influencing BAC:
• Body weight
• Alcohol content
• Number of beverages consumed
• Time since consumption
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BAC Calculation
Male
BAC =
Female
BAC =
Burn-off rate of 0.015 percent per hour, but can vary:
0.071 (oz) (% alcohol)
body weight
0.085 (oz) (% alcohol)
body weight
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Henry’s Law
When a volatile chemical is dissolved in a liquid and is brought to equilibrium with air, there is a fixed ratio between the concentration of the volatile compound in the air and its concentration in the liquid; this ratio is constant for a given temperature. THEREFORE, the concentration of alcohol in breath is proportional to that in the blood.
This ratio of alcohol in the blood to alcohol in the alveolar air is approximately 2,100 to 1. In other words, 1 ml of blood will contain nearly the same amount of alcohol as 2,100 ml of breath.
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Field Tests
Preliminary tests—used to determine the degree of suspect’s physical impairment and whether or not another test is justified
Psychophysical tests—three basic tests:
• Horizontal gaze nystagmus (HGN): follow a pen or small flashlight, tracking left to right with one’s eyes. In general, wavering at 45 degrees indicates 0.10 BAC.
• Nine-step walk and turn (WAT): comprehend and execute two or more simple instructions at one time
• One-leg stand (OLS): maintain balance; comprehend and execute two or more simple instructions at one time
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The Breathalyzer
More practical in the field Collects and measures alcohol content
of alveolar breath
Breath sample mixes with 3 ml of 0.025 percent K2Cr2O7 in sulfuric acid
and water:2K2Cr2O7 +3C2H5OH + 8H2SO4 2Cr2(SO4)3 + 2K2SO4 + 3CH3COOH + 11H2O
Potassium dichromate is yellow; as concentration decreases, its light absorption diminishes, so the breathalyzer indirectly measures alcohol concentration by measuring light absorption of potassium dichromate before and after the reaction with alcohol.
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Generalizations
During absorption, the concentration of alcohol in arterial blood is higher than in venous blood.
Breath tests reflect alcohol concentration in the pulmonary artery. The breathalyzer also can react with acetone (as found in diabetics),
acetaldehyde, methanol, isopropyl alcohol, and paraldehyde, but these are toxic and their presence means the person is in serious medical condition.
Breathalyzers now use an infrared light-absorption device with a digital readout. Prints out a card for a permanent record.