NOTES
FORENSIC TOXICOLOGY
 Toxicology is the study of drugs and poisons, and their interactions
and effects on the body.
 Anything can be a poison (any substance taken in sufficient
quantities, causing a harmful or deadly reaction). The key is
“sufficient quantities”.
 Forensic Toxicology is the application of toxicology to the law,
including
1. Workplace or forensic drug testing
2. Postmortem toxicology
3. Human performance testing
 Role of Forensic Toxicologist
a)
b)
c)
d)
e)
Studies bodily fluids and tissues for drugs and/or poisons
May conduct examination of personal effects and empty containers
May have extremely minute quantities to test
Must detect, identify and quantify the toxicity
Assess the state of inebriation of an automobile or industrial accident
victim
f) Determine whether someone died from a poison or from natural causes
g) Assess whether drugs played a role in a perpetrators actions or in
someone’s seizure, coma.
 The first toxicological test dates back to 1775, when Swedish chemist Karl
Scheele discovered a way to prove that arsenic was the culprit in a suspicious
death.
Looking for toxins:
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Most poisons work their mischief within the cells of the body and leave behind
no visible footprints. The Medical Examiner collects fluids and tissues from a
body and analyzes for the presence or absence of toxins.
Mercury, lead, arsenic, antimony, selenium, and many other metals can kill you,
and they’ve caused accidental, suicidal, and homicidal deaths for many years.
Collecting samples:

The best places to get samples for testing are the locations where chemicals
enter the body, where they concentrate and along routes of elimination:
o BLOOD - the toxicologists’ most useful substance. You can find
essentially any drug and its major metabolites in the blood.
o URINE- toxicologists can often find substances in greater concentrations
in the urine than in the blood. Easily sampled with a cup.
o STOMACH CONTENTS – Critical in cases where investigators suspect
poison or drug ingestion or overdose.
o LIVER – Many drugs, particularly opiates, tend to concentrate in the liver
and the bile, so investigators can measure them even when the blood
shows no traces.
o VITREOUS HUMOR – the liquid in the eyeball is fairly resistant to
putrifaction and in severely decomposed corpses, in may be the only
remaining fluid. Substance levers in the vitreous lag behind blood levels
by 1-2 hours, so testing reflects the concentration of the toxin in the
blood 1-2 hours earlier.
o HAIR – hair absorbs heavy metals and other drugs
o INSECTS – certain drugs tend to concentrate in the tissues of bugs that
feed on corpses.
Determining the cause and manner of death:
 Natural: The cause of death may be of natural causes, like a heart
attack, but a drug such as amphetamines may be a contributory
factor.
 Accident: Most accidental poisonings occur at home and often
involve children.
o In adults, accidental poisoning most often occurs because
a product is mislabeled, or a dose is miscalculated, or
two or more drugs are incompatible.
 Suicide: the most common manner of death in poisonings, and the
most common agent used is carbon monoxide. Other common
agents are prescription drugs.
 Homicide: Much more common in the past. Homicidal poisionings
occur most often at home, meaning the killer usually knows about
the victims habits and has access to the victims food, drink, and
medications.
Understanding the testing procedures:
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Literally thousands of drugs and chemicals are harmful, addictive, or lethal
which can cause huge problems for a toxicologist. Clues at the scene often
point toward a particular drug or poison.
When testing for drugs, toxins, or poisons, the toxicologist typically follows a 2tier approach.
Presumptive tests are used for initial screening (easier and cheaper). When
positive, the results indicate that a particular substance may be present.
 Color tests are chemical tests in which a reagent is added to a
substance (blood, urine or tissue) being tested. A color change occurs
whenever the suspected chemical is present.
Examples: In the Marquis test the reagent turns
Purple in the presence of heroin and morphine;
The Scott test is a color test for cocaine. The
Solution will turn blue is cocaine is present.
 Immunoassays involve an antigen-antibody reaction. The toxicologist
adds an antibody that can specifically id the suspected substance to the
sample. A reaction gives a positive result.
 Thin-layer chromatography is an inexpensive screening test that
identifies hundreds of compounds at once by separating compounds
according to how far they move through an absorbent material when
combined with a solvent.
 Gas chromatography is a method of separating compounds according to
their respective sizes, shapes, and chemical properties.
 Ultraviolet spectroscopy takes advantage of the fact that different
compounds absorb or reflect light in differing amounts and at varying
wavelengths.
Confirmatory tests are used only after presumptive tests find the possible
presence of a drug or toxin. They are more expensive and time-consuming, but
they establish the identity of the specific drug present. The most important
confirmatory test used by the toxicologist is Mass spectrometry.
DRUGS
 A drug is a natural or synthetic substance that is used to produce
physiological or psychological effects.
 In the US, more than 75% of the evidence evaluated in crime labs is
drug related. This deluge of drug specimens has forced the
expansion of existing crime labs and the creation of new ones.
Many concerned forensic scientists see this as a serious distraction
from time that should be devoted to evaluating evidence related to
homicides and other serious crimes.
 Approximately 23 million people in the US use illicit drugs.
o Psychological dependence = the conditioned use of a
drug caused by underlying emotional needs
o Physical dependence = the physiological need for a drug
brought about by its regular use and characterized by
withdrawal illness when administration of the drugs stops
abruptly.
The results of a forensic toxicologist (chemist) will have a direct
bearing on the process of determining the guilt or innocence of a
defendant. If a specimen is found to be a specific drug, or not, the
forensic chemist must be prepared to support and defend the validity of
the results in a court of law.
 Collection and Preservation of Drug Evidence:
o The main objective here is to prevent loss and or crosscontamination of the contents of any drug evidence. Often,
the original container in which the drug was seized will suffice
to meet these requirements.
ALCOHOL
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Approximately 40% of traffic deaths in the US are alcohol-related.
Today 90 million Americans drink alcohol regularly, and 10 million are addicted
or have severe problems in coping with their drinking habits. It is estimated that
about 40% of violent crimes involve the use of alcohol.
Alcohol appears in the blood within minutes after ingestion. When all of the
alcohol has been absorbed (stomach and small intestines) a maximum alcohol
level is reached in the blood.
Elimination of alcohol throughout the body is accomplished through oxidation
(the combination of oxygen with other substances to produce new products)
and excretion (breath, perspiration and urine). Oxidation takes place almost
entirely in the liver. (one drink/hour)
Toxicologists have had to develop specific procedures for measuring alcohol
intoxication.
Determination of Blood Alcohol Concentration (BAC)
 Analyzing brain tissue best. Brain and Blood concentrations are directly
proportional, so blood best for living individuals ;)
 Either blood or breath can be analyzed for quantity of alcohol consumed.
 Breath testing devices operate on the principle that the ratio between the
concentration of alcohol in alveolar breath and its concentration in blood is
fixed.
 Testing for intoxication –
1. Breath testing
a) Most widespread
b) A breathalyzer measures alcohol content in the alveolar (deep in lungs)
c) It requires 1 – 1.5 liters of breath
d) For accuracy, avoid “mouth alcohol” such as belching, or recent mouthwash.
2. Field Sobriety
a) Preliminary test performed to ascertain the degree of a suspect’s physical
impairment
b) Psychological tests – horizontal gaze, walk and turn, one-leg stand
c) Preliminary Breath Test – handheld breath tester uses a fuel cell to measure
alcohol content
d) Used to establish probably cause for more thorough breath or blood tests
3. Blood Analysis – high degree of accuracy using gas chromatography
a) Clean area with non-alcohol disinfectant
b) Refrigerate blood until delivered to the lab
c) Postmortem blood should be collected from a variety of bodily sites.
 Metabolism involves the body’s ability to breakdown chemicals. Three steps1. Absorption – alcohol appears in the blood minutes after consumption
2. Distribution – after absorption, alcohol becomes distributed uniformly
throughout the “watery” parts of the body. Factors affecting absorption:
a) Speed of consumption
b) Percentage of alcohol content
c) Quantity of alcohol consumed
d) Quantity and type of food in the stomach
3. Elimination – the boy begins to eliminate alcohol. Two methodsa) Oxidation – in the liver
b) Excretion – through breath, urine and perspiration
Blood Alcohol Laws
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A person with a blood-alcohol concentration of 0.08% is considered under the
influence of alcohol in the US. (.04% for commercial truck drivers and bus
drivers)
For driving a vehicle in Finland, France, Germany, Ireland, Japan, the
Netherlands , Norway and Australia - 0.05% - in Sweden - 0.02%
A blood alcohol concentration of .08% means  .08grams of alcohol/100milliliters of blood
Other Toxins/Poisons
 Environmental poisons : Some examples are radon, formaldehyde,
asbestos, lead, carbon monoxide, arsenic, cadmium, and mercury.
 Poisonous Invertebrates: Examples include: Banana spiders, hobo
spiders, scorpions, and white-tailed spiders.
 Poisonous plants: Examples include: Aconite, baneberry, black
locust, buckwheat, crown vetch, death cap mushrooms, and
dogbane.
 Food borne poisons: Examples: Salmonella, Escherichia coli, and
Shigella.
 Household poisons: Examples: insecticides, oven cleaners, antifreeze, bleach, drain cleaners, and spot removers.
 Poisonous animals: Blowfish, brown snake, vipers, cobras, poison
dart frog, and platypus.