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Forensic Toxicology

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

  2. 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

  3. Forensic Toxicology • Evaluation of contraband material –Examples include: • Seized drugs • Methamphetamine or other clandestine drug labs

  4. 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

  5. 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

  6. 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

  7. 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

  8. 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 asopiates • 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

  9. 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

  10. 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

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

  12. 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

  13. 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

  14. 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

  15. 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

  16. 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

  17. 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

  18. Prescription Medications • Sedative Hypnotics • Cardioactive agents • Antipsychotic drugs • Antiepileptic drugs • Antidepressants

  19. Non-Medicinal Agents • Alcohol • Cyanide • Carbon monoxide • Hydrocarbons

  20. 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

  21. 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

  22. 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

  23. 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

  24. 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

  25. 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

  26. 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

  27. 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

  28. 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

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

  30. 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

  31. 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

  32. 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