Forensic Toxicology


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Forensic Toxicology

  1. 1. Forensic Toxicology
  2. 2. Toxicology <ul><li>toxicologist </li></ul><ul><ul><li>detect and identify drugs and poisons in body </li></ul></ul><ul><ul><ul><li>fluids </li></ul></ul></ul><ul><ul><ul><li>tissues </li></ul></ul></ul><ul><ul><ul><li>organs </li></ul></ul></ul><ul><ul><li>employed in </li></ul></ul><ul><ul><ul><li>crime laboratories </li></ul></ul></ul><ul><ul><ul><li>medical examiner’s offices </li></ul></ul></ul><ul><ul><ul><li>hospitals </li></ul></ul></ul>
  3. 3. Methodology <ul><li>toxicologist often presented body fluids and/or organs and asked to examine them for drugs & poisons </li></ul><ul><li>many potential concerns/obstacles to this process </li></ul><ul><ul><li>usually no clue as to what type of substance will be present </li></ul></ul><ul><ul><ul><li>general screening employed to narrow down thousands of possibilities to just one item </li></ul></ul></ul>
  4. 4. Methodology <ul><ul><li>presence of substances need to be identified when only nanograms or at best micrograms ( ɥ L) are present </li></ul></ul><ul><ul><li>the body changes substances through it’s metabolism </li></ul></ul><ul><ul><ul><li>what was injected/ingested is not what is extracted </li></ul></ul></ul>
  5. 5. Methodology <ul><ul><li>every chemical is processed and stored in different areas of the body = chemical fate </li></ul></ul><ul><ul><li>when substance is detected, identified, and quantified a substance, the toxicity of the substance must be assessed </li></ul></ul><ul><ul><ul><li>published info to reference as far as toxic levels but… </li></ul></ul></ul><ul><ul><ul><li>interpretations of cataloged information must be made to account for each individual case </li></ul></ul></ul>
  6. 6. Techniques <ul><li>specimen extracted </li></ul><ul><li>identification of substance </li></ul><ul><ul><li>screening procedures </li></ul></ul><ul><ul><ul><li>gas chromatography </li></ul></ul></ul><ul><ul><ul><li>thin layer chromatography </li></ul></ul></ul><ul><ul><ul><li>immunoassay </li></ul></ul></ul><ul><ul><li>confirmation tests </li></ul></ul><ul><ul><ul><li>gas chromatography </li></ul></ul></ul><ul><ul><ul><li>mass spectrometry </li></ul></ul></ul>
  7. 7. Techniques <ul><li>immunoassay </li></ul><ul><ul><li>predominantly a presumptive test </li></ul></ul><ul><ul><li>creation of antibodies that are specific to a particular drug </li></ul></ul><ul><ul><ul><li>antigen-antibody reaction will take place if these antigens are added to a body fluid sample that contains the drug </li></ul></ul></ul>
  8. 8. Techniques <ul><li>immunoassay </li></ul><ul><ul><li>EMIT – Enzyme-Multiplied Immunoassay Technique </li></ul></ul><ul><ul><ul><li>to check someone for drug “A”, </li></ul></ul></ul><ul><ul><ul><li>analyst will add “A” antibodies to the urine as well as chemically labeled drug “A” to the body </li></ul></ul></ul><ul><ul><ul><li>any drug already in urine will compete with the labeled drug added to bind with the antibodies </li></ul></ul></ul><ul><ul><ul><li>quantity of labeled drug left uncombined is measured </li></ul></ul></ul><ul><ul><ul><li>this value is related to the amount of the drug originally in the urine sample </li></ul></ul></ul>
  9. 9. Techniques <ul><li>thin layer chromatography </li></ul><ul><ul><li>much like paper chromatography but with different materials </li></ul></ul><ul><li>gas chromatography </li></ul><ul><ul><li>liquid sample is vaporized into gas that is separated in chamber </li></ul></ul><ul><ul><li>recorder graphs the peaks of gases separated </li></ul></ul><ul><ul><li>each drug/substance has it’s own “signature” chromatogram </li></ul></ul>
  10. 10. Techniques <ul><li>mass spectrometry </li></ul><ul><ul><li>an analytical tool to identify substances by the mass and abundance of its individual ions </li></ul></ul><ul><ul><li>often linked to a gas chromatography chamber as the “recorder” </li></ul></ul><ul><ul><li>if this GC/MS is linked to a computer, this system can detect and ID substances present in only one-millionth of a gram quantities </li></ul></ul>
  11. 12. Techniques <ul><li>spectrophotometry </li></ul><ul><ul><li>an analytical tool to identify substances by the way the chemical absorbs different wavelengths of light </li></ul></ul><ul><ul><li>can be accomplished with two different sets of wavelengths </li></ul></ul>
  12. 13. Techniques <ul><li>spectrophotometry </li></ul><ul><ul><ul><li>ultraviolet & visible wavelengths </li></ul></ul></ul><ul><ul><ul><ul><li>result is a UV/V spectrum </li></ul></ul></ul></ul><ul><ul><ul><ul><li>does not provide a definitive result, rather establishes probable identity </li></ul></ul></ul></ul><ul><ul><ul><ul><li>eliminates thousands of possibilities from consideration </li></ul></ul></ul></ul><ul><ul><ul><li>infrafred wavelengths </li></ul></ul></ul><ul><ul><ul><ul><li>result is an IR spectrum </li></ul></ul></ul></ul><ul><ul><ul><ul><li>equivalent to a fingerprint for a specific substance </li></ul></ul></ul></ul>