FORENSIC SCIENCE Toxicology

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FORENSIC SCIENCEToxicology
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Why do Toxicology?

• Toxicology can
• Be a cause of death
• Contribute to death
• Cause impairment
• Explain behavior

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OUR STUDY

• Drugs
• Poisons

Basically, toxicology involves the separation,
detection, identification and measurement of the
drug and/or poison.
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Testing

• PDRs--Physicians Desk Reference
• Field Tests--presumptive tests
• Lab Tests--conclusive tests

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Analysis of Drugs

• Controlled Substances Act
• Schedule I--heroin, LSD
• Schedule II--morphine, methadone
• Schedule III--barbiturates, amphetamines
• Schedule IV--other stimulates and depressants
• Schedule V--codeine

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DRUG IDENTIFICATION

• Screening tests or presumptive tests
• Color tests
• Microcrystalline test--a reagent is added that
  produces a crystalline precipitate which are
  unique for certain drugs.

• Confirmation tests
• Chromatography
• Spectrophotometry
• Mass spectrometry

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Presumptive Color Tests

• Marquis--turns purple in the presence of most
  opium derivatives and orange-brown with
  amphetamines
• Dillie-Koppanyi--turns violet-blue in the
  presence of barbiturates

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Presumptive Color Tests

• Duquenois-Levine--turns a purple color in the
  presence of marijuana
• Van Urk--turns a blue-purple in the presence of
  LSD
• Scott test--color test for cocaine

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Confirmation TestsChromatography

• Techniques for separating mixtures into their
  component compounds
• Includes two phases--one mobile and one
  stationary that flow past one another
• As the mixture separates it interacts with the
  two phases.

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Types of Chromatography

• Paper
• Thin Layer
• Gas
• Pyrolysis Gas
• High Pressure Liquid (HPLC)

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Paper Chromatography

• Stationary phase--paper
• Mobile phase--a liquid solvent
• Capillary action moves the mobile phase through
  the stationary phase

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Thin Layer Chromatography

• Stationary phase--a thin layer of coating on a
  sheet of plastic or glass (usually aluminum or
  silica)
• Mobile phase--a liquid solvent

from www.lbp.police.uk
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Retention Factor (Rf)

• If the Rf value for an unknown compound is close
  to or the same as that for the known compound,
  the two compounds are most likely similar or
  identical (a match)

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GC Analysis

• Shows a peak that is proportional to the quantity
  of the substance present
• Uses retention time instead of Rf for the
  quantitative analysis

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Pyrolysis Gas Chromatography

• Used when a sample does not readily dissolve in a
  solvent
• If heating this sample decomposes it into gaseous
  products, these products can be analyzed by CGC
• A pyrogram is the visual representation of the
  results

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Mass Spectrometry

• Gas chromatography has one major drawback--it
  does not give a specific identification. By
  teaming a gas chromatograph with a mass
  spectrometer, this is accomplished.
• The mixture is separated first in a gas
  chromatograph. The GC column is directly
  attached to the mass spectrometer where a beam of
  electrons is shot through the sample molecules.

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MS (cont.)

• The electrons cause the molecules to lose
  electrons and become positively charged. These
  are unstable and decompose into many smaller
  fragments. These fragments pass through an
  electric or magnetic field and are separated
  according to their masses.
• NO TWO SUBSTANCES PRODUCE THE SAME FRAGMENTATION
  PATTERN.

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Human Analysisfor Drugs

• Blood
• Urine
• Vitreous
• Bile

• Liver tissue
• Brain tissue
• Kidney tissue
• Spleen tissue

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If all those buried in our cemeteries who were
poisoned could raise their hands, we would
probably be shocked by the numbers.
--John Trestrail
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POISONERS in HISTORY

• Olympiasa famous Greek poisoner
• Locustapersonal poisoner of Emperor Nero
• Lucretia Borgiafather was Pope Alexander VI
• Madame Giulia Toffanacommitted over 600
  successful poisonings, including two Popes.
• Hieronyma Sparaformed a society to teach women
  how to murder their husbands
• Madame de Brinvilliers and Catherine
  DeshayesFrench poisoners.
• AND many others through modern times.

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Symptoms of VariousTypes of Poisoning

• Type of Poison Symptom/Evidence
• Caustic Poison (lye) Characteristic burns around
  the lips and mouth of the victim
• Carbon Monoxide Red or pink patches on the chest
  and thighs. Unusually brighter red lividity
• Sulfuric acid Black vomit
• Hydrochloric acid Greenish-brown vomit
• Nitric acid Yellow vomit
• Phosphorous Coffee brown vomit. Onion or garlic
  odor
• Cyanide Burnt almond odor
• Arsenic, Mercury Pronounced diarrhea
• Methyl (wood) or Nausea and vomiting,
• Isopropyl (rubbing) alcohol
  unconsciousness, possibly blindness

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Points to Know about aPoison

• Form
• Common color
• Characteristic odor
• Solubility
• Taste
• Common sources
• Lethal dose
• Mechanism
• Possible methods of administration
• Time interval of onset of symptoms.

• Symptoms resulting from an acute exposure
• Symptoms resulting from chronic exposure
• Disease states mimicked by poisoning
• Notes relating to the victim
• Specimens from victim
• Analytical detection methods
• Known toxic levels
• Notes pertinent to analysis of poison
• List of cases in which poison was used

from Criminal Poisoning by John Trestrail
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Evidence

• Class
• Presumptive or screening tests can be used to
  determine that it is a drug.
• Individual
• Chromatography, especially in conjunction with
  mass spectrometry, will specifically identify a
  drug or poison and its components.

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Alcohol in theCirculatory System

• Forensic Science
• Toxicology Unit

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How to measure Alcohol ingested

• Two ways to measure alcohol in the blood
• 1. Direct chemical analysis of blood
• 2. Measure alcohol content of the breath

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Pathway of Blood

• 20 of alcohol ingested is absorbed thru stomach
  walls into the portal vein
• Remaining alcohol passes into the small intestine
• Once in the blood the alcohol goes to the liver
  and moves up to the heart
• Eventually, blood makes its way to the lungs

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Alveoli

• 250 million in lungs, located at the terminal
  ends of bronchial tubes
• It is the surface of these alveolar sacs that
  blood flowing through the capillaries comes into
  contact with fresh oxygenated air in the sacs

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Pathway cont.

• CO2, alcohol, or any other volatile substance
  will move from the capillaries into the air sacs
  to be exhaled
• Oxygen moves into the air sacs

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Henrys Law

• When a volatile liquid (alcohol) is dissolved in
  a liquid (blood) and is brought to equilibrium
  with air (alveolar breath) there is a fixed ratio
  between the concentration of the volatile
  compound (alcohol) in the air (alveolar breath)
  and its concentration in the liquid (blood) and
  this reaction is constant for a given temperature
  (34C)
• The ratio of alcohol in the blood to alcohol in
  alveolar air is approx. 2100 to 1..in other
  words 1 mL of blood will contain nearly the same
  amount of alcohol as 21 mL of alveolar breath.
• Thus.. Henrys Law becomes a basis for relating
  breath to blood alcohol concentration!

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Breath Test Instruments

• The Breathalyzer first developed in 1954
• Collects and measures alcohol content of alveolar
  breath
• I t is a spectrophotometer that has been designed
  to measure the absorption of light passing thru
  the K2Cr2O7 (potassium dichromate) solution at a
  single wavelength

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IR absorption and/or with fuel cell

• Alcohol present is captured in breath chamber
• a beam of infrared light is aimed through the
  chamber
• A filter is used to select a wavelength of IR
  light at which alcohol will absorb
• Information is processed by a microprocessor and
  the percent blood-alcohol concentration is
  displayed on a digital readout
• It is also printed on a card to produce a
  permanent record of the test results

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Field Sobriety Testing

• Performed to ascertain the degree of the
  suspects physical impairment and whether or not
  an evidential test is justified.

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Psychophysical tests

• Horizontal gaze nystagmus
• Refers to an involuntary jerking of the eyes as
  they move to the side
• When bac is 0.10 the jerking will begin before
  the eyeball has moved 45 degrees to the side

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• Higher bac will cause jerking at smaller angles
• Barbituates/depressants can cause nystagmus

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Walk TurnOne-Leg Stand

• Tasks test the subjects ability to comprehend
  and accomplish two or more simple instructions at
  one time