Forensic science toxicology
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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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Forensic science toxicology




  • Poisons

  • Due Today:

  • Over the counter medications lab from yesterday

  • Til Death do us part video organizer

Forensic file 3

Forensic File #3

What is the difference between ACUTE and CHRONIC poisonings?

Today s assignments

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

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

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

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

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 system1

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

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 etoh1

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

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

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

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

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

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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