FORENSIC SCIENCE Toxicology

1. FORENSIC SCIENCEToxicology

2. 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

3. 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

4. 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

5. 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

6. 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 Infaredlight 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

7. What is Henry’s law? • Describes the relationship between the alcohol content of breath and the alcohol content of blood at a given point in time. • It defines the quantity of breath that would contain the same amount of alcohol as a given quantity of blood

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

9. 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

10. 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

11. 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