Chapter 10 Forensic Toxicology Introduction: Toxicologists

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Chapter 10Forensic Toxicology
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Introduction Toxicologists

• Detect and identify
• presence of drugs and poisons
• body fluids
• Tissues
• organs
• Work in crime laboratories and medical examiners
  offices
• May also reach into hospital laboratories and
  health facilities to identify a drug overdose or
  monitor the intake of drugs
• Major branch measurement of alcohol in the body
  (violations of criminal law)

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Toxicology of Alcohol
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Toxicology of Alcohol

• Analysis of alcohol example
• Primary objective of forensic toxicology
• Detection and isolation of drugs in the body
• Purpose of determining influence on human
  behavior
• Alcohol (ethanol, ethyl alcohol)
• Colorless liquid
• Normally diluted with water
• Consumed as a beverage
• CNS depressant

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Alcohol Levels

• Alcohol appears in the blood within minutes
• Slowly increases in concentration while it is
  being absorbed from the stomach (20) and the
  small intestine
• All the alcohol absorbed ? maximum alcohol level
  reached in the blood
• Post absorption period begins
• Concentration slowly decreases until a zero level
  is again reached
• Factors influencing rate of absorption
• Time taken to consume the drink
• Alcohol content
• Amount consumed
• Food present in the stomach.

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Alcohol Levels

• Elimination of alcohol throughout the body
• Oxidation in the liver
• Excretion unchanged in breath, urine,
  perspiration
• Measure
• Blood alcohol
• Alcohol content in the breath direct proportion
  to the blood concentration

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Alcohol and Circulatory System

• Closed circulatory system consisting of a heart,
  arteries, veins, and capillaries
• Alcohol absorbed from the stomach and small
  intestines
• Carried to the liver where the process of its
  destruction starts
• Blood, carrying alcohol, moves to the heart,
  pumped to the lungs
• Carbon dioxide and alcohol leave the blood
• Oxygen enters the blood in the air sacs (alveoli)
• Carbon dioxide, alcohol exhaled

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Human Circulatory System
Figure 102  Dark vessels contain oxygenated
blood light vessels contain deoxygenated blood.
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The Respiratory System
Figure 103b  The trachea connects the nose and
mouth to the bronchial tubes. The bronchial tubes
divide into numerous branches that terminate in
the alveoli sacs in the lungs.
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Gas Exchange In The Lungs
Figure 103a  Blood flows from the pulmonary
artery into vessels that lie close to the walls
of the alveoli sacs. Here the blood gives up its
carbon dioxide and absorbs oxygen. The oxygenated
blood leaves the lungs via the pulmonary vein and
returns to the heart.
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Circulation

• YouTube - Circulation animation
• YouTube - St. Joseph Aspirin Pumps Your Blood -
  Banjo Man
• YouTube - Pumps Your Blood

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Driving Risk
Figure 1010  Diagram of increased driving risk
in relation to blood-alcohol concentration.
Courtesy U.S. Department of Transportation,
Washington, D.C.
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Breath Test Instruments
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Breath Testers

• Operate on the principle of infrared light
  absorption
• Becoming increasingly popular within the law
  enforcement community
• Designed to capture a set volume of breath
• Captured breath is exposed to infrared light

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Breathalyzer

• Glass ampoule
• Potassium dichromate
• Sulfuric acid
• Water
• Silver nitrate catalyst
• Alcohol oxidized to acetic acid
• Potassium dichromate destroyed

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Figure 104  Schematic diagram of a Breathalyzer.
Courtesy Draeger Safety, Inc., Breathalyzer
Division, Durango, Colo.
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Infrared Breath-testing Instrument

• Breathalyzer phased out in 1970s
• Replaced by computerized instruments
• Free of chemicals
• IR radiation absorption

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Infrared Breath-testing Instrument

• Degree of the interaction of the light with
  alcohol in the captured breath sample that allows
  instrument to measure blood alcohol
  concentration in breath

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Considerations in Breath Testing
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Considerations in Breath Testing

• Instruments can be connected to external standard
• Sampled before an after subject test
• Unit must measure alveolar breath (deep lung
  breath)
• 1,5 liters breath needed

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Considerations in Breath Testing

• Avoid measuring mouth alcohol
• Regurgitation
• Belching
• Recent intake of alcohol
• Alcohol mouthwash
• No foreign material 15-20 minutes before test
• Duplicate measurements within a few minutes

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Field Sobriety Testing
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Field Sobriety Testing

• Estimate motorists degree of physical impairment
  by alcohol
• Evidential test for alcohol justified?
• Preliminary breath-alcohol content
• Portable, handheld, roadside breath tester
• Contains fuel cell the oxidizes alcohol
• Produces electrical current proportional to
  alcohol content

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Field Sobriety Testing Nystagmus Test

• Horizontal gaze nystagmus test
• Involuntary jerking as eye moves to side
• Subject unaware of jerking
• 0.10 blood alcohol ? jerking before movement
  of 45 degrees

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Field Sobriety TestingDivided Attention Tests

• Comprehension of two instructions
• Walk and turn
• Stand heel to toe
• Walk nine steps heel-toe
• Turn around
• Repeat
• One-leg stand
• Balance standing with heels together
• Stand on one leg 30 seconds
• Count aloud while standing

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Analysis for Blood Alcohol
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Gas Chromatography Testing

• Most widely used approach for determining alcohol
  levels in blood
• Blood must be
• Drawn under medically accepted conditions
• By a qualified individual
• Nonalcoholic disinfectant be applied before the
  suspects skin penetrated with a sterile needle
  or lancet
• Preservation
• Anticoagulant and a preservative added
• Sealed in an airtight container and stored in a
  refrigerator

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Alcohol Dehydrogenase

• Used inclinical labs
• Enzyme plus NAD
• NADH formed measured spectrophotometrically

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Alcohol and Law
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Figure 1011  To use this diagram, lay a
straightedge across your weight and the number of
ounces of liquor youve consumed on an empty or
full stomach. The point where the edge hits the
right-hand column is your maximum blood-alcohol
level.
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Figure 1011  The rate of elimination of alcohol
from the bloodstream is approximately 0.015
percent per hour. Therefore, to calculate your
actual blood-alcohol level, subtract 0.015 from
the number in the right-hand column for each hour
from the start of drinking.
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Alcohol and Law

• Uniform and reasonable blood-alcohol standards
• American medical association
• National safety council
• Between 1939 and 1964
• Blood-alcohol level in excess of 0.15 percent w/v
• By 1965 was lowered to 0.10 percent
• In 1972 lowered again to 0.08 percent w/v

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Alcohol and Law

• Starting in 2003
• States that have not adopted the 0.08 percent per
  se level
• Lose part of their federal funds for highway
  construction
• National highway traffic safety administration
  recommended an implied consent law
• Adopted by all states by 1973
• States that the operation of a motor vehicle on a
  public highway
• Automatically carries stipulation that a driver
  will submit for a test for alcohol intoxication
• Or subject to loose of the license

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Schmerber v. California

• Blood drawn when Schmerber treated for accident
  injuries
• Supreme court
• Emergency situation
• No time to obtain warrant
• Drawn under medicallly accepted procedures
• Must be considered case-by-case

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Role of the Toxicologist
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Role of the Toxicologist

• Drugs and poisons
• Body fluids and/or organs
• Requested to examine them for the presence of
  drugs and poisons
• Toxicologist is forced to use general screening
  procedures
• Without supportive evidence
• Victims symptoms
• Postmortem pathological examination,
• Examination of the victims personal effects

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Role of the Toxicologist

• Not dealing with drugs at concentration levels
  found in powders and pills
• Dissipated and distributed throughout the body
• Body is an active chemistry laboratory
• Substances enter and completely leave the body in
  the same chemical state
• Must be prepared to assess the toxicity of the
  drug or poison

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Role of the Toxicologist

• Living person
• Blood
• Tox screen 10 ml minimum
• Alcohol 5 ml
• More blood needed for alcohol-drug interaction
• Urine
• Taken in duplicate in separate containers
• cases

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The Analytical Scheme
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The Analytical Scheme
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The Analytical Scheme

• Detect, isolate, and specifically identify toxic
  drug substances
• 90 of drugs
• Alcohol
• Cocaine

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The Analytical Scheme

• Extract from appropriate biological fluids,
  tissues, and organs
• Based on a large number of drugs either acidic or
  basic

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pH

• Definition of pH
• Acids H donors
• Bases H acceptors
• Minus log of H ion concentration

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pH Scale
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Categories by pH
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The Analytical Scheme

• Identify the drug substance present
• Screening
• Confirmation

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Techniques Used in Toxicology
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The Screening Step

• Quick insight into likelihood that specimen
  contains a drug substance
• Positive results arising from screening test
• Tentative at best
• Must be verified with a confirmation test
• Most widely used screening tests
• Thin-layer chromatography
• Gas chromatography
• Immunoassay

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The Confirmation Step GC-MS

• Confirmation test of choice.
• Gc separates the sample into components
• MS represents a unique fingerprint pattern that
  can be used for identification
• May be required to provide an opinion on the
  drugs effect on an individuals natural
  performance or physical state

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Figure 1013  The combination of the gas
chromatograph and the mass spectrometer enables
forensic toxicologists to separate the components
of a drug mixture and provides specific
identification of a drug substance.
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Heavy Metals

• Metals included
• Arsenic
• Bismuth
• Antimony
• Mercury
• Thallium
• Reinsch test
• Dissolve in HCl
• Copper strip
• Silvery or dark coating

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Carbon Monoxide

• Combines with hemoglobin
• Interferes with oxygen carrying capacity of blood
• Methods
• Spectrophotometric spectrum carboxyhemoglobin
• Liberate CO measure by GC

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Carbon Monoxide

• Expressed as saturation
• Middle aged person greater than 50-60 sat.
  fatal
• With alcohol (0.20) 35-40 sat. fatal
• Chain smokers 8-10 sat.
• Suicide 5-10 minutes in garage
• Fire victim low CO ? murder

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Significance of Toxicological Findings
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Significance of Toxicological Findings

• Used to assess influence on behavior
• Alcohol levels proscribed by law
• Other drugs
• Only estimate of effects
• Live person
• Police report of behavior (DRE)
• Deceased person
• Levels in various organs
• Info on use history
• Synergy between drugs

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Drug Recognition Expert (DRE)
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Drug Recognition Expert (DRE)

• Standardized methods for examining automobile
  drivers suspected of being under influence of
  drugs
• Ensure that each subject tested in a routine
  fashion
• DRE must complete a standard drug influence
  evaluation form
• Usually cannot determine which specific drug was
  ingested
• Reliable data from both the DRE and forensic
  toxicologist required to prove drug intoxication

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Categories of Drugs

• CNS depressants
• CNS stimulants
• Hallucinogens
• Phencyclidine
• Inhalants
• Narcotic analgesics
• Cannabis

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Summary