Toxicology: Poisons and Alcohol. Chapter 8 Toxicology: Poisons and Alcohol 2 Kendall/Hunt Publishing...

Toxicology: Poisons and Alcohol

Chapter 8


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



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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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.

Chapter 8



More Information

Read more about forensic toxicology at truTV’s Crime Library:

http://www.crimelibrary.com/criminal_mind/forensics/toxicology/2.html

Toxicology: Poisons and Alcohol. Chapter 8 Toxicology: Poisons and Alcohol 2 Kendall/Hunt Publishing...

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