Forensic Toxicology

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Forensic Toxicology

• Toxicology study of poisons
• Forensic toxicology - examination of all aspects
  of toxicity that may have legal distinctions

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Forensic Toxicology

• Postmortem drug testing
• Examples of this testing include
• Overdoses
• Suspected poisoning
• Workplace drug testing
• All Federal agencies require preemployment drug
  testing
• Some random testing of employees in specific
  occupations
• 90 of largest U.S. corporations require drug
  free urine as a condition of employment

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Forensic Toxicology

• Evaluation of contraband material
• Examples include
• Seized drugs
• Methamphetamine or other clandestine drug labs

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Testing Samples Blood

• Blood- most important specimen in postmortem
  toxicology
• Toxin correlates more closely with lethal outcome
  in blood than other specimens
• Two specimens of 50 100 milliliters are taken
• One from heart
• One from a peripheral site

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Testing Samples Urine

• Most frequently used in preemployment screening
  due to
• Large amount can be easily collected
• Does not require venipuncture
• Urine - collected in postmortem investigation

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Testing Samples Gastric Contents

• Gastric Contents- may be tested in sudden death
  of person who had large quantities of lethal
  agent in stomach
• Highly toxic substances maybe found in small
  quantities in blood in contrast to large amount
  in stomach
• In suicide cases, large amounts of drug in
  stomach may be present

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Testing Sample Eye

• Vitreous humor eye is an isolated body area,
  and the vitreous humor is resistant to
  putrefaction,
• Vitreous humor may be only fluid remaining in
  decaying cadaver
• Chemical abnormalities may be found here
• Postmortem increases of potassium or hypoxanthine
  may assist in establishing time of death

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Testing Samples Liver

• Liver organ most heavily involved in drug
  metabolism
• Bile drains from liver and may be very rich in
  certain types of drugs- such as opiates
• Hair- not commonly used in forensic
  investigations due to the following factors
• Drugs are present in extremely low
  concentrations- picogram to milligram
• Controversy regarding how drug entered hair
  internally or externally

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Workplace Drug Testing

• Workplace drug testing is concerned with testing
  for drugs of abuse
• NIDA National Institute of Drug Abuse
• Program created to curb drug use
• Required preemployment drug testing as a
  condition of federal employment
• Only specific drugs can be screened

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• Drugs which may be tested under NIDA
• Amphetamines and methamphetamine
• Opiates (including morphine and codeine)
• Phencyclidine
• Cocaine
• Cannabinoids marijuana
• Other laboratories may test for barbituates,
  hallucinogens, etc

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Types of Drugs

• Amphetamines- stimulants which create an
  excitatory condition
• Amphetamines are primarily synthetic
• Amphetamines (speed) and methamphetamine (meth)
  are most widely known

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Types of Drugs

• Opiates ability to cause profound euphoria
• best examples are morphine and codeine
• Grown predominantly in Southeast Asia
• Pharmaceutical use is as an analgesic or pain
  reliever
• Drug abusers dissolve oxycodone and inject it to
  gain euphoria

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Types of Drugs

• Phencyclidine better known as PCP
• Originally designed as a surgical anesthetic for
  humans, but found to be unsatisfactory due to
  certain side effects
• A feeling of euphoria
• A feeling of detachment from world
• Higher doses can cause severe perceptive
  distortions
• psychosis, violent behavior, paranoia and
  hallucinations
• After regular use of PCP, results can be found in
  urine for about one week

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Types of Drugs

• Cocaine stimulant that resembles
  methamphetamine in abusive potential
• Derived from plant of coca leaf, Erythroxylon
  coca
• Plant primarily grows in South America Andes
  mountain range
• Normally extracted with hydrochloric acid
• Cocaine is converted to Benzoylecgonine and can
  be tested for and found in urine up to 3 days
  following use of cocaine

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Types of Drugs

• Cannabis sativa plant
• Many psychoactive compounds are derived from this
  plant
• THC- tetrahydrocannabinol is primary active
  agent, and present in 2-6 of weight of cannabis
  or marijuana
• Hashish- oily extract of cannabis that produces
  up to 12 THC level

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Types of Drugs

• Marijuana mary jane, pot, dope, weed
• Typically smoked in a rolled cigarette- known as
  a joint, or through a bong pipe
• Reaches peak concentrations in blood 10-20
  minutes after inhalation
• Effect lasts about 2 hours
• Euphoria, perceptive alterations, memory
  impairment , mood swings and intoxications
• Can be tested for in urine and discovered for up
  to two months

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Prescription Medications

• Internal organ damage may occur as a result of a
  primary medical condition not allowing person to
  metabolize drug
• As a result, drug may build up in blood to lethal
  concentrations

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Prescription Medications

• Sedative Hypnotics
• Cardioactive agents
• Antipsychotic drugs
• Antiepileptic drugs
• Antidepressants

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Non-Medicinal Agents

• Alcohol
• Cyanide
• Carbon monoxide
• Hydrocarbons

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Alcohol

• Blood alcohol is measured by
• Gas chromatography- gas flowing through a tube
  separates compounds by size, weight and chemical
  reactivity with coating of tube
• Blood is preferred specimen for measuring
  alcohol, and should be placed in a gray top tube
  that contains sodium flouride as a preservative
• Concentrations of 500 milligrams per deciliter
  are consistent with cause of death

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Analysis

• Screening- test for presumptive positives and is
  sensitive to presence
• Confirmation confirm presence through results
  which are both sensitive and specific
• Use of both creates a double positive

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SCREENING

• Immunoassays- tests which use antibodies and
  allow reagents to react only with a substance
  that recognizes that antibody
• Absorbance spectrophotometry, flouresence or
  chemiluminescence are used to complete
  measurement

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SCREENING

• Thin layer chromatography
• Specimen is extracted into organic solvent and
  Spotted on plate coated with silica
• Plate is placed into tank that contains a mobile
  phase which migrates to plate and separates
  whatever chemicals are present

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SCREENING

• Ultraviolet Visible Spectrophotometry (UV-VIS)
• Certain drugs absorb light at different wave
  lengths
• Each drug produces a spectrum that allows
  identification of the drug through absorbance at
  a certain wavelength and other spectral
  characteristics

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• Technology of this method is limited by
• Ultraviolet visible spectra tend to be
  characterized by broad number of peaks and many
  spectra lack highly specific features
• High risk of misidentification when another drug
  or chemical is present that absorbs light in that
  specific region
• Remedi auto analyzer has greatly improved UV-VIS
  detection of drugs

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Confirmatory Analyses

• Gas Chromatography
• relies upon separation and emergence of substance
  from other components, and measurement of
  retention time from the column
• Gas Chromatography- Mass Spectrometry
• allows for separation and measurement of
  retention time of elements in a gas
  chromatographic column, and mass spectrum
  analysis of substance

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Confirmatory Analyses

• Chemical Ionization type of mass spectrometry
  in which a molecule reacts under relatively low
  energy with a reagent gas rather than fragmenting
  extensively
• Tandem Mass Spectrometry fragment produced in
  first stage of electron impact is isolated and
  subjected to further bombardment produces a
  daughter spectrum

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Confirmatory Analyses

• Liquid Chromatography-Mass Spectrometry
• Technology in which a liquid chromatograph
  replaces the gas chromatograph
• Mixture is swept into liquid instead of a gas
• Since no heat is needed for conversion to gaseous
  state, it is compatible with every organic
  chemical

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METALS

• Metals are accurately measured by colorimetric
  testing
• Simple reagents needed
• Inexpensive photometer needed

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Metal Analyses

• Atomic Absorption Spectrophotometry (AAS)
• Ions in metal are reduced to atoms, and specific
  wavelength of light is used to raise a valence
  electron of metal to high energy state
• Detector measures light before and after sample
  is introduced

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Metal Analyses

• Neutron Activation Analyses (NAA)
• Highly specialized for metal detection
• Sample placed in presence of low energy neutrons
  and undergoes radioactive changes
• Products of this emit gamma rays or x- rays
• Characteristics of emitted radiation allow
  analyst to identify metals present and measure
  concentration

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Metal Analyses

• Inductively Coupled Plasma Mass Spectrometry
  (ICP-MS)
• Best and most modern technique for metal analysis
• Argon atoms in ICP-MS torch are subjected to
  radio frequency energy which makes them collide
  and drives temperature to over 6000 degrees
  Celsius
• Several metals may be analyzed at a time
• Very low detection limits of metal present are
  achieved