Forensic Toxicology

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Transcript Forensic Toxicology

Forensic Toxicology
SFS3. Students will analyze the use of toxicology…in forensic investigations.
a. Classify toxins and their effects on the body.
b. Compare the effects of alcohol on blood alcohol levels with regard to gender, and
according to the law.
c. Evaluate forensic techniques used to isolate toxins in the body.
• How can you distinguish among the
types of toxins and their effects on
the body?
• How are different forensic
techniques used to isolate and
identify toxins in the body?
• What factors influence the effects of
alcohol on the body and why?
Forensic toxicology is…
• the use of detecting and identifying
the presence of drugs and poisons
in body fluids, tissues, and organs to
aid medical or legal investigation.
• The primary concern for forensic
toxicology is not the legal outcome
of the toxicological investigation or
the technology utilized, but rather
the obtaining and interpreting of the
• Earliest recorded use of poison
was Socrates’ execution in 339 BC
via ingestion of hemlock
• In the Renaissance, poisoning
became an art, occupation, even a
• Philippus Theophrastus
Aureolus Bombastus von
Hohenheim (aka
Paracelsus [~1525])
observed that any
substance could be a
poison, depending on its
"All things are poison and nothing is without
poison; only the dose makes a thing not a
• Mathieu Orfila, chairman
of the legal medicine
department at La
Sorbonne in France,
published a book in
• This was the first attempt to
systematically study and classify
• Orfila was the first to articulate
the fact that poisons must be
absorbed, or enter the blood, to
manifest their effects.
• In the U.S., forensic toxicology
did not develop until the early
20th century in New York
• Dr. Alexander Gettler (lead FT in
NYC medical examiner lab) is
considered this country’s first
forensic toxicologist.
Poison vs. Toxin vs. Venom
• Poison – substances that cause
biological disturbance when
absorbed in sufficient quantities
– Toxin – produced biologically
• Venom – injected via bite or sting
Cyanide is poisonous
Botulinum is toxic
Rattlesnakes are venomous
Types of Poisons
• Microbicide – used to reduce infectivity of
– chlorine, peroxide, antibiotics
• Herbicide – used to kill unwanted plants
– 2,4-D, atrazine, glyphosate (Roundup)
• Pesticide – used to kill unwanted animals
– DDT, pyrethrin, nicotine
Types of Toxins
• Hemotoxin – destroy red blood cells
– pit vipers
• Necrotoxin – cause cell & tissue death
– brown recluse spider, “flesh-eating
• Neurotoxin – affect the nervous system
– Black widow spider, scorpions
Types of Venoms
• Fang-released
– snakes, centipedes, spiders
• Sting-released
– bees/wasps/ants, scorpions
• Other methods
– Hairs (caterpillars)
– Tentacles (jellyfish)
– Saliva (Gila monster)
– Fins (lionfish, stingrays)
• Dosage is indeed important, but
so are…
– The form of the substance
• Insoluble vs. soluble
– How it enters the body
• Inhalation vs. injection vs. ingestion
– Body weight/age/sex of victim
– Time period of exposure
• Acute vs. chronic toxicity
– Interactions with other chemicals
in the body
• Synergistic vs. antagonistic
• LD50 – refers to amount of
substance that would kill 50% of
test population within 4 hrs.
– Typically represented as
(mg subst. / kg weight)
LD50 information
<1 mg/kg = taste to drop
~50 mg/kg = teaspoon
~500 mg/kg = ounce
~5000 mg/kg = pint
Sugar - LD50=29700
Caffeine - LD50=192
Ethanol - LD50=7060
Nicotine - LD50=48
Salt - LD50=3000
Cyanide - LD50=6.4
Botulinum toxin - LD50=0.00005
Roles of the Toxicologist
• Must identify one of thousands of
drugs and poisons
• Must find nanogram to microgram
quantities dissipated throughout the
entire body
• Not always looking for exact
chemicals, but metabolites of
desired chemicals (ex. heroin 
morphine within seconds)
Toxicology Procedures
• Presumptive/Screening
– quick test to narrow down possibilities
– spot/color tests
• Confirmation
– determines exact identity
– thin-layer/gas chromatography, IR
spectroscopy, mass spectrometry
• Marquis Test:
– Turns purple in the presence of opiates
– Turns orange-brown in presence of
• Scott Test:
– Turns blue in the presence of cocaine
• Duquenois-Levine:
– Turns purple in the presence of tetrahydrocannabinal
Marquis Test
Scott Test
Confirmatory Tests
• Microcrystalline Tests: Identifies
drug by using chemicals that react to
produce characteristic crystals
• Chromatography: Separates drugs
and gives tentative ID
• Mass Spectrometry: Chemical
“fingerprint” – no two drugs fragment
the same
• IR Spectroscopy: IR light is
absorbed by different chemicals
Microcrystalline Tests
Mass Spectrometry
IR Spectroscopy
Testing Samples
• Divided into 2 samples
– 1st sample is for screening test
– 2nd sample is for confirmatory test
• Only done for samples that test
positive during screening
Testing Samples
• Blood
– 10 mL whole blood, anticoagulant,
– More expensive, but more accurate,
can detect hours to days usage
• Urine
– Samples always given under direct
– Easy, cheap, can detect hours to days
Testing Samples
• Hair samples
– Collected from scalp or body
– Can detect days to months usage
• Saliva
– Can detect hours to ~2 days usage
• Vitreous humor
– Only used post-mortem
– Resists putrefaction, can detect usage
after embalming
Regulatory Agencies
• Food and Drug Administration
• Environmental Protection Agency
• Consumer Product Safety
• Department of Transportation
• Occupational Safety and Health
Controlled Substances Act
• In 1970, federal law established 5
schedules of classification of
controlled substances based on
– Drug’s potential for abuse
– Potential to physical and psychological
– Medical value
• Federal law also controls materials
that are used in making drugs and
those that are manufactured to
resemble drugs
• DEA and FDA set classifications
Controlled Substances Act
• Abuse
– Inappropriate (misuse) or
unwarranted use of substances,
either legal (alcohol, prescriptions)
or illegal
Controlled Substances Act
• Dependence
– Physical dependence occurs
when the drug becomes
necessary for the body to function
• Withdrawal symptoms can lead to
• NOT the same as addiction
– Psychological dependence
occurs when a person thinks they
need a drug to function normally.
Drug Schedules
• Schedule I:
Drugs with high potential for abuse and
addiction, NO medical value
Ex: heroin, LSD, MDMA (Ecstasy),
marijuana, GHB, peyote, psilocybin
• Schedule II:
Drugs with high potential for abuse and
addiction, have some medical value with
restrictions (no refills)
Ex: PCP, cocaine, Ritalin, oxycodone,
morphine, methamphetamine
Drug Schedules
• Schedule III:
Drugs with less potential for abuse and
addiction, currently acceptable for medical
use (no more than 6 refills)
Ex: Vicodin, codeine, ketamine, anabolic
• Schedule IV:
Drugs with low potential for abuse and
addiction, currently acceptable for medical
use (no more than 6 refills)
Ex: Valium, Xanax, Rohypnol
Drug Schedules
• Schedule V:
Drugs with low potential abuse, lowest
potential dependency, acceptable for
medical use
• Ex: antitussive, antidiarrheal, analgesic
Classes of Drugs
• Stimulant
– Enhances the function or activity of the
brain; causes alertness and motivation
• Depressant
– Relieves anxiety and muscle spasms;
causes sedation and confusion
• Hallucinogen
– Causes subjective changes in perception,
thought, emotion and consciousness
• Narcotics (opioids)
– Slowed physical activity, analgesia,
Toxicology of Alcohol
• Alcohol is absorbed through the
stomach and intestine
• Once absorbed, alcohol is:
– Oxidized in liver by alcohol
dehydrogenase—turned into
acetic acid (vinegar)
– Excreted by breath, perspiration,
and kidneys—turned into carbon
dioxide and water
Blood Alcohol Content
• Relates amount of alcohol per
volume of blood
• Legal intoxication limit in US is
0.08, meaning 0.08 grams of
ethanol per 100 mL of blood
(4.5-5.5 mL absorbed [~1 tsp])
>0.20 – Stupor
>0.40 – Unconsciousness/death
and the Law
intoxicated =
0.15% BAC
1965: intoxicated
= 0.10% BAC
2003: intoxicated
= 0.08% BAC
At least we don’t live in France,
Germany, Ireland, or Japan
(0.05%), Sweden or China (0.02%),
and Russia or Saudi Arabia (0.00%)
Factors that Affect Alcohol
• Amount consumed
– More alcohol = more absorbed
• Alcohol content
– Maximum absorption with 20-25% alcohol
• Time of consumption
– Maximum absorption with 30 minute
consumption period
Factors that Affect Alcohol
• Presence of food in stomach
– Food in stomach slows absorption of
• Body weight
– More weight = more water in body to dilute
• Gender
– Females have more fat tissue = less water
Time of Consumption &
Food in Stomach on BAC
Body Weight and Time of
Consumption on BAC
Men vs. Women
Blood Alcohol Content
• Measuring the quantity of alcohol in
the blood system (BAC) determines
the degree to which someone is
• Two methods of making this
– Measurement of alcohol content in
– Measurement of alcohol in breath
BAC Testing
• Blood alcohol is metabolized at the
rate of 0.015 per hr, so…
– If your BAC is 0.08, how long will it take
for your BAC to be 0.00?
0.08 ÷ 0.015 = 5.33 hrs
• Alcohol is identical to the BAC tester
1 can of beer = 1 glass of wine = 1 shot of liquor
Breath Tests
• Evidence has shown that the ratio of
alcohol in the blood to alcohol in
alveoli air is approx. 2100 to 1—This
is a basis for relating breath to
blood-alcohol concentration.
• One instrument used for breath tests
is called The Breathalyzer.
The Breathalyzer
The Breathalyzer Con’t
• The Breathalyzer traps 1/40 of 2100
milliliters of alveolar breath, so it, in
essence, measures the alcohol
concentration present in 1/40 of a
milliliter of blood.
• Developed in 1954, it was originally
based on a color change observed
by spectroscopy
Other Breath Tests
• Infrared spectrophotometer technology
• Electrochemical fuel cell technology
These instruments are used more
recently because they don’t depend upon
chemical reagents and are entirely
Infrared and Fuel Cell
Breath Tests
• Infrared Breath Test
uses infrared
wavelengths to test for
alcohol or other
interferences in the
• Fuel Cell Test
converts fuel (alcohol)
and oxygen into a
measurable electric
Field Sobriety Testing
• Two reasons for the field
sobriety test:
1. Used as a preliminary test to
ascertain the degree of the
suspect’s physical impairment
2. To see whether or not an
evidential test is justified
Field Sobriety Testing
• Field sobriety testing consists of a
series of psychophysical tests and a
preliminary breath test (typically
done with a handheld fuel cell tester)
• These tests are preliminary and
nonevidential in nature—they only
serve to establish probable cause
requiring a more thorough breath or
blood test
Field Sobriety Tests
• Horizontal Gaze Nystagmus
– Involuntary eye jerk as eye moves horizontally
• Walk and Turn (divided attention tasks)
• One-Leg Stand