1 / 61

Forensics: Chapter 10

Forensics: Chapter 10. FORENSIC TOXICOLOGY. OBJECTIVES: . Describe general categories of drugs and their effects on humans. Describe and demonstrate tests used to detect heavy metals, toxins, alcohol, or other drugs inside or outside body tissues. Alcohol Statistics:.

wright
Download Presentation

Forensics: Chapter 10

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Forensics: Chapter 10 FORENSIC TOXICOLOGY

  2. OBJECTIVES: • Describe general categories of drugs and their effects on humans. • Describe and demonstrate tests used to detect heavy metals, toxins, alcohol, or other drugs inside or outside body tissues.

  3. Alcohol Statistics: • Current statistics indicate that ethyl alcohol (legal over-the-counter drug), is the most heavily abused drug in Western countries. • It is less toxic than methanol or isopropyl alcohol

  4. Sad Statistics: • U.S.: Approximately 17,500 automobile deaths (40% of all traffic deaths) are alcohol related with over two million persons per year requiring hospital treatment.

  5. The Job of a Toxicologist: • Toxicologists are charged with the responsibility of detecting and identifying the presence of drugs and poisons in body fluids, tissues, and organs.

  6. Absorption: • Passage of alcohol across the wall of the stomach and small intestine into the blood stream.

  7. Factors That Affect The Rate Of Alcohol Absorption: • quantity and type of food in the stomach • the alcoholic content of the beverage • the amount consumed • total time taken to consume the drink

  8. Blood & Brain: • Blood alcohol concentration is directly proportional to the concentration of alcohol in the brain.

  9. Maximum Blood-Alcohol Concentrations: • Depending on several factors, maximum blood-alcohol concentration may not be reached until 2 to 3 hours have elapsed from the time of consumption. • Under normal social drinking, it takes anywhere from 30 to 90 minutes from the time of final drink until the absorption process is completed.

  10. Other Sources for Alcohol Content: • When alcohol absorption is complete, alcohol will be distributed uniformly throughout the watery portions of the body. • If blood is not available to a medical examiner for alcohol content, there are always options of selecting a water-rich organ or fluid such as: 1. brain 2. cerebrospinal fluid 3. vitreous humor

  11. Alcohol Elimination: • Elimination of alcohol is accomplished through 2 processes: oxidation & excretion.

  12. Oxidation: • Combination of oxygen with other substances to produce new products. • Nearly all alcohol consumed is oxidized to CO2 and H2O. • Takes place almost entirely in the liver.

  13. Excretion: • Elimination of alcohol from the body in an unchanged state; alcohol is normally excreted in breath and urine. • Remaining portion of alcohol is excreted unchanged in the breath, urine, and perspiration. • The amount of alcohol exhaled in the breath is in direct proportion to the concentration of alcohol in the blood.

  14. Alcohol Is: • absorbed into the bloodstream • distributed throughout the body’s water • eliminated by oxidation and excretion

  15. Alcohol Elimination: • The elimination or “burn off” rate of alcohol varies in different individuals (0.015% w/v is about average)

  16. Under The Influence? • The extent to which an individual may be under the influence is usually determined in one of two ways: • direct chemical analysis of the blood for its alcohol content • measurement of the alcohol content of the breath

  17. What Happens When You Drink Alcohol? • After alcohol is ingested, about 20% of the alcohol is absorbed through the stomach walls. • The remaining alcohol passes into the blood through the walls of the small intestine.

  18. Human Circulatory System: • Humans have closed circulatory system. • It consists of arteries, veins and capillaries. • It is across the thin walls of the capillaries (particularly in the lungs) that the exchange of materials between the blood and the other tissues takes place.

  19. Blood Passages: • Artery – blood vessel that carries blood away from the heart. • Vein – blood vessel that transports blood toward the heart. • Capillary – tiny blood vessel across whose walls exchange of materials between the blood and the tissues takes place; receives blood from arteries and carries it to veins.

  20. Blood Alcohol Concentration: • Blood alcohol concentration is greater in arterial blood than in venous blood.

  21. Alveoli: • Small sacs in the lungs through whose walls air and other vapors are exchanged between the breath and the blood.

  22. Blood & Breath: • The ratio of alcohol in the blood to alcohol in alveolar air is approximately 2100 to 1.

  23. Henry’s Law: • Basis for relating breath to blood-alcohol concentration.

  24. Breath Tests: • Reflect the alcohol concentration in thepulmonary artery. • More accurately reflect the concentration of alcohol reaching the brain and, therefore, directly reflect the effects of alcohol on the subject.

  25. Breath Analysis: • Very useful in that it provides an easily obtainable specimen along with a rapid and accurate result.

  26. The Breathalyzer • Common breath-testing instrument. • Device for collecting and measuring the alcohol content of alveolar breath. • A type of spectrophotometer that measures the absorption of light by potassium dichromate before and after its reaction to alcohol. • Silver nitrate acts as a catalyst (substance that speeds up the rate of a chemical reaction but is not itself permanently changed by the reaction.

  27. Did You Know? • Some breath-testing devices for alcohol use infrared light to measure the quantity of alcohol trapped in a chamber.

  28. GC & Alcohol Testing: • Gas chromatography offers the most widely used approach for determining alcohol levels in blood (forensic labs normally use this device).

  29. Field Sobriety Tests (FST): • Preliminary tests normally performed to determine the degree of the suspect’s physical impairment and whether or not an evidential test is justified.

  30. Parts of A FST: • Field sobriety tests include: • One leg stand • Walk and turn • Horizontal gaze nystagmus • Portable roadside breath tester

  31. Collection and Preservation of Blood: • One blood is removed from an individual, it is preserved by: • Adding an anticoagulant and a preservative • Sealing it in an airtight container • Refrigerating it until delivery to the toxicology laboratory

  32. Anticoagulant: • Substance that prevents coagulation or clotting of the blood • Examples: EDTA or potassium oxalate

  33. Preservative: • Substance that stops the growth of microorganisms in blood • Examples: sodium fluoride

  34. Did You Know: • Failure to keep the blood refrigerated, storing for long periods of time, or to add the preservative results in a substantial decline in alcohol concentration.

  35. Alcohol Testing After Death: • Postmortem blood samples – • Ethyl alcohol may be generated in a deceased individual as a result of bacterial action. • Therefore, collection of numerous samples from different body sites is required (ex: heart, femoral and cubital veins, vitreous humor, urine )

  36. “Under the Influence”: • The blood alcohol concentration level for being presumed to be legally “under the influence” in most states is 0.08%.

  37. Alcohol & the DOT: • In 1992, the U.S. Department of Transportation (DOT) recommended that states adopt a 0.08 % blood alcohol concentration as the legal measure of drunk driving. • In 2003, any states not adopting this percent would lose part of their federal funds for highway construction. The 0.08% level applies only to noncommercial drivers and 0.04% for commercial truck and bus drivers.

  38. Did You Know? • Sweden has the lowest blood alcohol concentration in determining legal impairment level.

  39. Schmerber vs. California: • The leading case relating to the constitutionality of collecting a blood specimen for alcohol testing, as well as for obtaining other types of physical evidence from a suspect without consent. • In this case, blood was considered to be “non-testimonial” evidence.

  40. FYI: • Few substances enter and completely leave the body in the same chemical state. • The drug that is injected is not always the substance extracted from the body tissues.

  41. Metabolize: • Transforming a chemical in the body to another chemical for the purpose of facilitating its elimination from the body.

  42. FYI: • Heroin is almost immediately metabolized to morphine on entering the bloodstream (therefore, heroin will not be found in blood or urine).

  43. Capabilities of a Toxicologist: • Toxicologist capabilities are directly dependent on the input received from: • the attending physician • medical examiner • police/ police investigators

  44. Did You Know? • Alcohol and cocaine account for 90% or more of the drugs encountered in a typical toxicology laboratory.

  45. Acids & Bases: • A large amount of drugs fall into the categories: acids and bases • Acid – compound capable of donating a hydrogen ion to another compound. • Base – compound capable of accepting a hydrogen ion

  46. The pH Scale • The concentration of acids and bases are expressed in terms of a simple numerical value that relates to the concentration of the hydrogen ion in a liquid medium such as water. Chemists use the pH scale to do this. The scale runs from 0 to 14 (7 is neutral, less than 7 is acidic, greater than 7 is basic).

  47. Acidic & Basic Drugs: • Acidic Drugs include: Basic Drugs include: • Barbiturates Phencyclidine • Acetylsalicylic acid (aspirin) Methadone • Amphetamines • Cocaine

  48. Screen & Confirmation: • Once a specimen has been extracted and categorized as either acidic or basic, the toxicologist can then proceed to identify the drugs present. • This is a two step approach called: screening and confirmation

  49. Screening Tests: • Screening tests are tentative and must be verified by confirmation tests.

  50. 3 Most Widely Used Screening Tests in Toxicology Labs: • TLC (thin-layer chromatography) • GC (gas chromatography) • most sensitive & reliable when studying flammable residue • Immunoassay • results based on specific drug antibody reactions • can detect small concentrations of drugs in body fluids & organs

More Related