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FORENSIC SCIENCE Toxicology

FORENSIC SCIENCE Toxicology. Review. Poisons Due Today: Over the counter medications lab from yesterday Til Death do us part video organizer. Forensic File #3. What is the difference between ACUTE and CHRONIC poisonings?. Today’s assignments. Alcohol notes- from MHS website

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FORENSIC SCIENCE Toxicology

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  1. FORENSIC SCIENCEToxicology

  2. Review • Poisons • Due Today: • Over the counter medications lab from yesterday • Til Death do us part video organizer

  3. Forensic File #3 What is the difference between ACUTE and CHRONIC poisonings?

  4. Today’s assignments • Alcohol notes- from MHS website • BAC Detection lab- on table 1 • BAC calculations- front table • Work on PROJECT!!!!

  5. Things to know about Alcohol • Ethyl alcohol is a colorless liquid • Measure of intoxication is based on weight & absorption • Toxicology is typically gauged using blood • Blood-alcohol concentration is directly proportional to concentration in the brain • EtOH appears in the blood within minutes of consumption • Alcohol enters the bloodstream slowly and becomes uniformly distributed in watery portions of the body which is ~ 2/3 of the body volume

  6. Elimination of EtOH • Oxidation- the combination of oxygen with other substances to produce new products. • 95-98% EtOH is oxidized into carbon dioxide and water • This process takes place in the liver • Excretion- elimination of EtOH from body in unchanged state; EtOH is normally excreted in breath and urine, but may also be excreted in sweat • Exhaled EtOH is directly proportional to concentration in blood stream

  7. Path of alcohol in the body: • Mouth- alcohol enters body • Stomach: some alcohol gets into the bloodstream in the stomach, but most goes on to the small intestine • Small intestine: alcohol enters the bloodstream through the walls of the small intestine (villi) • Heart: pumps alcohol throughout the body • Brain: alcohol reaches the brain • Liver: alcohol is oxidized by the liver at a rate of about 0.5 oz per hour • Alcohol is converted to water, carbon dioxide and energy

  8. Movement of EtOH in circulatory system • Artery- blood vessel that carries blood away from the heart (oxygenated) • Vein- blood vessel that carries blood towards the heart (unoxygenated) • Capillary- tiny blood vessel across whose walls exchange materials between blood and tissue takes place; rec’s blood from arts. And carries to vns. • after ingestion to stomach, ~20% of EtOH is absorbed thru small intestine’s portal vein. Remaining EtOH passes into the blood thru walls of the small intestine

  9. Movement of EtOH in circulatory system • Once in the blood, it is carried to the liver where it’s destruction begins. • The blood is carried to the heart, entering the right atrium then the right ventricle, this is oxygen poor • Consequently pumped through the lungs, replenished with oxygen • Carbon dioxide and EtOH vapors are exchanged between blood and breath via alveoli • Also after emerging from lungs, oxygenated blood enters left atrium to left ventricle, into arteries to be moved all over the body

  10. Testing for EtOH • The breathalyzer was developed in 1954 • Widely used to test motorists suspsected of being under the influence up until the early 1990’s. This test measures the alcohol content of alveolar air. • Recent technology uses IV light absorption. These instruments operate on the same principle as spectrophotometers. Fuel cells convert a fuel & and oxidant into an electrical current; the current is proportional to the quantity of EtOH in the breath

  11. Testing for EtOH • Field sobriety tests are normally performed to ascertain the degrees of a suspect’s physical impairment & whether or not an evidential test is justified. • Psychophysical tests include the walk & turn, the one leg stand, & the observation of horizontal nystagmus, which is the involuntary jerking of the eye as it moves side to side

  12. Blood testing • Gas chromatography is the most widely used approach for determining EtOH levels in blood • GC is normally used by forensics labs

  13. Collection & preservation of blood • Blood must always be drawn under medically acceptable conditions by a qualified individual. • Preservation is best ensured when sealed in an airtight container with an anticoagulant & preservative added. • Anticoagulants- prevent clotting • Preservatives- prevents microorganism growth • Postmortem collection requires extra precautions. EtOH may be generated by bacterial, therefore blodo should be collected from a # of sites: heart, femoral artery, cubital vein, vitreous humor of eye and urine

  14. What is Henry’s law? • When volatile chemical (alcohol) is dissolved in a liquid (blood) & is brought to equilibrium with air (alveolar breath), there is a fixed ratio between the concentration of the volatile compound (alcohol) in air (alveolar breath) and its concentration in the liquid (blood), and this ratio is constant for a given temperature.

  15. What is the law regarding alcohol? • Blood toxication level: 0.10 • Refusal to take a test for alcohol intoxication- must submit to a test or be subject to lose license for some designated period

  16. How do you calculate BAC? • Use consistent formulas- male & female differ in amount of body water content so you have different formulas • For males: BAC= 0.071 x (volume consumed in oz) x % alcohol body weight in lbs • For females: BAC= 0.085 x (volume consumed in oz) x % alcohol body weight in lbs. We typically process out 0.05 per hour after drinking

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