Chapter 12

Forensic Toxicology

Toxicology

Study of adverse effects of chemical on living organisms

Postmortem toxicology

identifies presence of drugs, gases, metals, and other toxic chemicals in human fluid/organs and determines, if any, as contributing factors in the individual’s death

Human performance toxicology (behavioral toxicology)

Measures the amount of alcohol/drugs in a living person’s blood/breath and estimates their role in modifying human performance or behavior

Steps of postmortem toxicological investigation (always begins with a case history of the deceased)

1. Age, sex, weight, medical history
2. Medication administered before death
3. Autopsy findings
4. Drugs that were available to the decedent
5. Interval between the onset of symptoms and death

During the autopsy, they collect postmortem specimens for analysis

Pathologist

The ___________,____________, and ________ are organs that should be collected for postmortem toxicological analysis

brain, liver, kidney

If it is suspected that a poison was administered orally, the ________ should be analyzed first

gastrointestinal contents

Postmortem blood from the ___________ has been found to contain higher concentrations of drugs than other parts of the body

heart

The most widely abused drug in Western Countries is

ethyl alcohol

A BAC of .08% is equivalent to ________ grams of alcohol per 100 mL of blood

0.08

Is the field sobriety test a presumptive or confirmatory test?

presumptive

Legislation that triggers sanctions at a certain BAC level is called "___" legislation.

per se

Most of the alcohol a person drinks is absorbed into the bloodstream through the ___ ___.

small intestine

The higher the proportion of water in an organ, the (higher/lower) the concentration of alcohol.

higher

Alcohol in the body is oxidized in this organ: ___.

liver

More than 90% of the ethyl alcohol that enters the body is completely oxidized to ___ ___.

acetic acid

Alcohol that is not metabolized is excreted in the sweat, the urine, or the ___.

breath

One milliliter of blood with contain the same amount of alcohol as ___ milliliters of expired breath.

2100

The more alcohol present in the breath sample, the (greater/smaller) the absorbance observed by intoxilyzer.

greater

The most reliable method of determining BAC is by ___ ___.

gas chromatography

T/F In badly decomposed bodies, poisons are more likely to be found in the vitreous humor

True

T/F The rate at which the body moves alcohol from the blood is constant for any one individual.

True

T/F Failure to properly preserve the blood sample will always give a BAC that is falsely high.

True

T/F When sampling blood from a corpse, it is best practice to collect blood samples from multiple sites on the body.

True

BAC from 2am if it was at 0.07% at 4am?

0.1% (diff of 0.015% every hour)

Analysis of Toxicology Specimens:
All starts with the case history

– How was the poison taken?

Analysis of Toxicology Specimens:
If taken orally:

– Check the gastrointestinal (GI) contents first since it may still hold unabsorbed poisons or drugs
– Urine should be analyzed next
May contain intact poison or one of its metabolites

Analysis of Toxicology Specimens:
The liver is the next organ that usually has the highest concentration of poisons

Liver detoxifies the body of chemicals:
• By either oxidizing or reducing the poison
• By binding the poison to a sugar that is naturally present in the liver

Poisons

Over 2 million poisonings occur in the U.S. each year
Poisons can be categorized as:
– Inorganic: Mercury, Arsenic, Lead
– Organic: Chloroform, Ipecac, Heroin
– Radiological: Any radioactive species
– Biological: Certain plants, disease

Corrosive Poisons

A substance that destroys tissues on contact
These include strong acids and bases
– HCl, H2SO4, NaOH, KOH
– These substances are contained in many household items such a drain cleaner and car batteries
– How dangerous a substance is depends on its pH
• Determined by the concentration of H+ ions

Corrosive Poisons

Corrosive compounds attack the peptide bond to break down the protein, and damage the tissue

pH Scale

Very Acidic: Battery Acid
Very Basic: Over Cleaner

Metabolic Poisons

• A poison that interferes with essential metabolic process in the body
• Cyanide Poisoning (CN-) – either as a gas (hydrogen cyanide) or as a solid(potassium or sodium cyanide)
– It inhibits an enzyme called cytochrome C oxidase
– Binds to iron (III) in the enzyme and prevents its reduction to iron (II)
– If this reduction does not occur, oxygen cannot be used by the cells

Metabolic Poisons

Carbon Monoxide (CO)
-a colorless, tasteless, and odorless gas that is a product of incomplete combustion
-Makes the skin turn pink and the lips turn cherry red

Toxic Metals

Some metals are toxic in very small amounts
• Metals of particular concern include berylium (Be), cadmium(Cd), chromium (Cr), lead (Pb), mercury (Hg), thalium (Tl), and arsenic (As)
• Heavy metals and As are highly reactive with sulfhydryl groups(-SH) present in the active site of enzymes involved in oxygen transport

Reinsch Test

it works when metal ion reacts in acid to form a colored coat on copper metal
– Suspect tissue or blood are dissolved in a Hydrochloric acid solution and a strip of copper is added to the solution
– It is only a presumptive test
– The presence of the metal needs to be confirmed by an analytical test such as ICP-OES or X-ray

Organic Poisons

Very common poison due to availability, even if that is by illegal methods
• Are typically administered to incapacitate a victim
• Immunoassays tests are used to test the specimens for opiates, barbiturates, and other classes of prescription drugs

Organic Poisons

• Organic poisons can be acidic or basic
• Toxicologists can change the pH of a solution by adding an acid or a base to extract a potential poison
• Used to concentrate the poison in order to be used for further analysis

Interpretation of Toxicological Information

• Once the specimens are analyzed, the forensic toxicologist must assemble the results, study them, and determine the cause of death
• Must determine:
– How the poison entered the body
– How much poison was administered
– Whether enough poison was ingested to cause death directly or indirectly
• The concentration of drugs in postmortem blood is not uniform throughout the body
– Highest concentration of drugs have been found in heart blood
• It has been found to increase as the interval between death and autopsy lengthens

Interpretation of Toxicological Information

Analysis of tissue specimens allows toxicologists to estimate the “minimal administered dose” of a drug or poison
• How is the minimal administered dose determined?
– Determine the concentration of the drug or poison in as many different organ tissues as possible
– Concentration of each drug or poison in each separate organ tissue is multiplied by the total weight or volume of that organ
– Add the amount of drugs found in all organs
– Total amount is the minimal administered dose

Marijuana DUI and DUIDHuman Performance Testing

• The most commonly used human performance tests are those employed to determine whether an individual is driving a car under the influence of alcohol (DUI) or drugs (DUID).
• Currently, laws governing the use of a motor vehicle after using marijuana are either:
– Effect-based laws: Evidence of impairment.
– Per se DUID laws: Assumed to be guilty if the drug concentration exceeds a defined level.
No requirement to obtain evidence of impairment.
– Zero tolerance laws.

Immunoassay Test for Marijuana Use

• A rapid, on-site oral fluid screening.

Field Sobriety Testing

• Field sobriety tests include a structured process that may include:
– An officer interview
– Psycho-physiological tests (eye exam and coordination tests)
– Physical examination of the suspect
– Evaluation of suspect statements
– Toxicology exam (breath, blood, and/or urine)

Alcohol

a depressant that acts on the central nervous system.

Alcohol and The Law

• 1800s, first sanctions were imposed by the railroad industry
• 1939, Indiana became the first state to enact a “drunk driving” law in which BAC was used as the basis determining a person’s sobriety.
• 1964, Grand Rapids Study was published

Grand Rapids Study

Grand Rapids study was the first of its kind to
– Connect motor vehicle crashes to BAC
– Provide scientific base for court cases
– Let room open for more research
• It took 20 years for the study to finish and established a scientific foundation for“per se”.
• Meaning, the study provided reference for minimum penalty thresholds
• It’s still used to develop programs to reduce drinking and driving

Results of Grand Rapids study

validated the effectiveness of breathalyzers and their accuracies

Alcohol and The Law

By 1973, “implied consent” laws require motorists to takeBreathalyzer test or face sanctions (lose their license)
• 1980’s found the growth and development of both civilian(MADD) and government groups that pushed for harsher laws against DUI
• U.S. Department of Transportation recommends that all states adopt a 0.08% BAC as the legal definition of drunk driving
– States that had not adopted it lost federal highway construction funds
– Commercial drivers have lower limit of 0.04% BAC

Alcohol Metabolism

As ethyl alcohol travels through the GI tract, it is absorbed into the bloodstream (stomach 20%, small intestine, 80%).
• Once in the bloodstream, the alcohol travels to the brains and effects central nervous system (CNS).
• Factors which influence absorption rate:
– Rate of gastric emptying
– Presence of food in the stomach
– Concentration of the ethyl alcohol
– Rate of alcohol consumption

Alcohol Metabolism Chart

Blood Ethanol after 1 drink
Empty stomach: (about) 100mg/dL
Full stomach: (about) 50mg/dL

Alcohol Metabolism

Ethyl alcohol gets into the body by absorption, which is a slow process
• The actual concentration of ethanol in a particular tissue in the body depends on the water content of that tissue
– The more water the organ contains, the higher the concentration of alcohol expected
• Ethanol concentrations in the tissues rapidly reach equilibrium with the BAC

Alcohol Metabolism

Alcohol like any toxin is eventually eliminated from the body
• During ethyl alcohol’s elimination process, it is transported to the liver, where enzymes catalyze the oxidation of the alcohol.
• More than 90% of the ethyl alcohol that enters the body is completely oxidized to acetic acid, primarily in the liver.
• The remaining alcohol that is not metabolized is excreted in either the sweat, urine, or breath.

Measuring BAC

BAC via blood at the time of an accident can be estimated via a simple equation
– Ca BAC at the time of the accident
– Ct BAC measured after the accident
– β is the rate at which body removes alcohol
• Different for every person
• Ranges from 12.5 mg/100 mL/hr to 25 mg/100 mL/hr
• Average is 18.7 mg/100 mL/hr

Breathalyzer

developed in 1954 by Dr. Robert Borkenstein. It based on Henry’s law which states that
At a constant temperature, the amount of a given gas that dissolves in a given type and volume of liquid is directly proportional to the partial pressure of that gas in equilibrium with that liquid.
-Based on Henry’s law, in humans the ratio of exhaled alcohol to blood alcohol is 2,100 to 1

Breathalyzer

The absorption of light by potassium dichromate is measured before and after its reaction with alcohol present in the suspect’s breath
• The absorption of light of the suspect sample is compared to a standard
• The higher the concentration of alcohol the more potassium dichromate will react and less will be available in the vial

Intoxilyzer

How? measures the infrared (IR) absorption in a specific wavelength to confirm the presence of ethanol
BAC? The amount of IR absorbed by a compound corresponds to the energy it takes to stretch or bend bonds in a specific organic molecule
Each molecule has an unique IR spectrum but presence acetone or acetaldehyde molecules can give a false positive
Unlike Breathalyzer, Intoxilyzer measures “deep lung” air not just if there is alcohol in the persons mouth

Alcosensor

an alcohol fuel cell that consists of a porous, chemically inert layer that is coated on both sides with a thin platinum layer, which is impregnated with an acid solution and has electrical wires attached to the platinum.
-Can be connected to a smartphone

Blood Testing

Carried out using a Gas Chromatograph-MassSpectrometer (GC-MS)
• Highly accurate and never gives a high false positive
– So accurate almost always admissible in court
• Blood must be properly taken and stored in an airtight container
– Container has an anticoagulant, which is intended to prevent clotting of the blood, as well as a preservative, which inhibit microorganisms from growing and contaminating the sample. Example-> EDTA

Blood Testing

In case of post mortem testing, blood samples from various locations and sometimes samples of urine and the vitreous humor
• After a person dies, bacteria grow in the cadaver and produce ethanol, which may lead to a falsely high BAC reading
• If blood samples collected from different locations produce similar BAC results the alcohol content was the result of alcohol consumption by the person before death

GC Analysis of BAC

When a blood sample is analyzed, the area under the peak is measured. By referring to the calibration curve, the forensic examiner can calculate the concentration of alcohol in the sample