1 FORENSIC SCIENCE Toxicology

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

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

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

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

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

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

Movement of EtOH in circulatory system u Artery- blood vessel that carries blood away from the heart (oxygenated) u Vein- blood vessel that carries blood towards the heart (unoxygenated) u Capillary- tiny blood vessel across whose walls exchange materials between blood and tissue takes place; rec’s blood from arts. And carries to vns. u 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 8

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

Testing for EtOH u The breathalyzer was developed in 1954 u 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. u 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 10

Testing for EtOH u Field sobriety tests are normally performed to ascertain the degrees of a suspect’s physical impairment & whether or not an evidential test is justified. u 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 11

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

Collection & preservation of blood u Blood must always be drawn under medically acceptable conditions by a qualified individual. u Preservation is best ensured when sealed in an airtight container with an anticoagulant & preservative added. u Anticoagulants- prevent clotting u Preservatives- prevents microorganism growth u 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 13

14 What is Henry’s law? u 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? u Blood toxication level: 0.10 u Refusal to take a test for alcohol intoxication- must submit to a test or be subject to lose license for some designated period

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