Forensic science toxicology
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FORENSIC SCIENCE Toxicology PowerPoint PPT Presentation

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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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  • 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

  • BAC Detection lab- on table 1

  • BAC calculations- front table

  • Work on PROJECT!!!!

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

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

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

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

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

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

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

Blood testing

  • Gas chromatography is the most widely used approach for determining EtOH levels in blood

  • GC is normally used by forensics labs

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

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.

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

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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