Forensic Toxicology

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Forensic Toxicology
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Deaths Investigated by Toxicologists

• Accidental Poisonings
• Drug Abuse Cases
• Suicidal Poisonings
• Homicidal Poisonings

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Questions Addressed by Toxicology

• Is a drug or poison present? What substance?
• How much of the substance is present? Is its
  concentration in the body sufficient to cause
  death?
• How was the drug/poison administered?

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General Classes of Poisons

• Gases (HCN, CO)
• Metallic Poisons (As, Sb, Pb, Li, Hg, Tl)
• Non-volatile Organics
• Corrosive poisions (strong acids and bases)
• Salts (NaCN, etc.)
• Alkaloids
• Pesticides

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Carbon Monoxide (CO)

• Normal level 1-3 (up to 10 in smokers)
• Fatal level at autopsy considered to be gt50 for
  a healthy middle-aged male
• CO prevents O2 binding to Hemoglobin in blood
• Suffocation
• CO victims have cherry pink color

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Metal poisons

• Most common As2O3
• Symptoms
• Vomiting
• Diarrhea
• Death within 24 hrs.
• Can be given over long period of time

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Alkaloids

• Nitrogen containing organic base
• Found in Plants and fungi
• Atropine (deadly nightshade)
• Strychnine
• Death from muscle over-stimulation
• Respiratory failure
• Spasms and convulsions

Strychnine
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Metabolism

• Drugs are changed by the body so that they can be
  made water soluble for excretion
• May not find toxin in body but metabolic product
  instead

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Measuring Blood Alcohol

• Venous Blood (invasive)
• GC
• UV spectra
• NAD to NADH
• Breath (Breathalyzer)
• Ethanol will reduce K2Cr2O7 to Cr2(SO4)3
• K2Cr2O7 is yellow and adsorbs light at 420nm
• Visible spectrometer detects decrease in
  absorbance at 420 nm to determine presence of
  Ethanol is blood

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Toxicological Analysis of Tissue

• Collect sample of all body fluids
• Collect samples from organs and tissues
• A forensic toxicologist cannot simply look for
  the presence of a toxin or drug in a body, she
  must understand how the body processes these
  molecules
• Toxicological analysis must start as soon as
  possible after a persons death

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Samples collected at autopsy

• Specimen collection--fluids
• Blood All available up to 100 mL
• Urine 100 ml (no preservative)
• Bile All available
• Vitreous All available
• Gastric contents 50 grams
• Specimen collection--soft tissue
• Liver 100 grams
• Brain 100-200 grams
• Kidney 50 grams
• Lung 50 grams
• Spleen 50 grams

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Extraction of toxins from fluid

• Drugs are either acidic or basic
• Acidic drugs can be extracted from acidic
  solutions with organic solvents (CHCl3)
• Acidic barbituates
• Basic alkaloids

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Identification

• Screening
• Immunoassay
• GC
• TLC
• Confirmation
• GC/MS

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Solid sample identification methods

• Color test
• Microcrytalline test
• Chromatography
• TLC
• GC
• HPLC
• Spectroscopy
• UV-Vis
• Infrared
• X-ray
• Mass Spectroscopy
• Immunoassay