1. Forensic Toxicology
Chapter 10

2. What is Forensic Toxicology?
The detection and identification of drugs or poisons present in body fluids, tissues and organs.

3. The Biggest Culprit
Alcohol is the most abused “drug” in the West and most likely the world.
40% of all traffic accidents are alcohol related.
So the most numbers of samples sent to forensic toxicology labs are alcohol related.

4. What is Alcohol? Colorless liquid
Organic compound
Carbon and hydrogen backbone with at least one hydroxyl group (OH)
Many types, depending on the number of carbons present
Humans consume Ethyl Alcohol or Ethanol
Colorless liquid
Produced when yeast ferment grain, fruit and other vegetation such as potatoes

5. Toxicology of Alcohol What happens to alcohol once it enters the body?
Consumption / Ingestion
Absorption into bloodstream
It then crosses the blood-brain barrier into neurons, affecting the Central Nervous System (CNS)
Elimination
Oxidation (alcohol is changed to other products)
Excretion (alcohol is unchanged)

6. How do we measure alcohol levels?
The most obvious measure of intoxication would be to see how much an individual has consumed
This is impossible for a forensic toxicologist for several reasons:
He wasn’t present (Duh!)
Person’s body weight varies
Rate of alcohol absorption into bloodstream varies

8. This is your brain on ethanol
The Absolute (no pun intended) best way to check for intoxication would be to check brain tissue
This is also impossible for obvious reasons – unless the person in question is dead.

9. The next best thing So forensic toxicologists concentrate on blood.
Blood circulates the consumed alcohol to ALL body tissues
The concentration of alcohol in the blood is directly proportional to the concentration of alcohol in the brain

10. The Route Alcohol Takes
Mouth  Esophagus  Stomach  Small Intestine  Bloodstream
Alcohol is absorbed across the lining of the small intestine, into the bloodstream (some absorption can occur across stomach wall also)
This happens within minutes of consumption
The blood concentration levels keep increasing as more and more alcohol gets absorbed across S.I.

11. The path alcohol follows to your brain, via bloodstream

12. The Rate of Absorption Several factors affect the rate of absorption:
The amount of alcohol consumed
What was the alcohol content (or proof) of the beverage?
The rate at with it was consumed (1 beer over 1 hour, or 1 beer over 1 minute)
How much food was in the stomach?

13. You need to absorb this material!
The longer it takes for all the alcohol consumed to be absorbed, the lower the peak alcohol concentration in the bloodstream.
Food in stomach hinders/slows absorption

14. Empty vs. Full Stomach

15. After Absorption
When all the alcohol is absorbed, its levels will be equally distributed in the “watery” tissues of the body (so not in fat, hair, nails, bones, etc.).
If blood is not available (dead body) – a forensic toxicologist can work with other body fluids and tissues – Cerebrospinal fluid, vitreous humor, or brain

16. BAC – Blood Alcohol Concentration
It is usually measured as mass per volume and expressed as a percentage.
For example, a BAC of 0.02% means 0.02 grams of alcohol per 100 grams of an individual's blood, or 0.2 grams of alcohol per 1000 grams of blood.
BAC can vary according to the person’s tolerance and metabolic rate

17. Can you tolerate it?
Tolerance to alcohol varies from one person to another, and can be affected by such factors as genetics, adaptation to chronic alcohol use, and synergistic effects of drugs.

18. Metabolism The breakdown of chemicals, including alcohol
The elimination of alcohol from the body depends upon the individual’s metabolism.

19. Elimination by Oxidation
Nearly all alcohol (95-98%) gets oxidized.
Oxidation – Ethanol is oxidized to produce carbon dioxide and water
Oxidation occurs almost entirely in the cells of the liver.
Oxidation of ethanol is performed by an enzyme called Alcohol Dehydrogenase in the following process.
(Acetaldehyde)
(Acetic Acid)
The Acetic Acid is then oxidized further into CO2 and H2O

20. Rate of Ethanol Oxidation
The rate of elimination via oxidation varies from individual to individual, depending upon their metabolic rate. Oxidation is also called “burn-off” and it reduces blood-alcohol concentrations.
Absorption must be complete in order for burn-off to reduce BAC levels.

21. Elimination by Excretion
The 2% of ethanol that is not eliminated by oxidation is excreted through the breath, urine and perspiration.
This excreted alcohol is not changed chemically – it remains ethanol.

22. Breath Dragon (Alveolar breath)
The amount of alcohol exhaled in the breath is directly proportionate to the concentration of alcohol in blood.
When air is exhaled, it contains CO2 and alcohol
Hence the “Breathalyzer” Test

23. Pulmonary Vein
Pulmonary Artery
Alveolar Breath

24. Breathalyzer
A breathalyzer (or breathalyser) is a device for estimating blood alcohol content (BAC) from a breath sample.
“Breathalyzer” is a brand name and was originally made by Smith and Wesson, but now is a generic term used for all such devices.
Measures alcohol found in alveolar breath.

27. Where’s the Proof?
Alcoholic proof is a measure of how much ethanol is in an alcoholic beverage, and is approximately twice the percentage of alcohol by volume
The proof number is twice the percentage of the alcohol content measured by volume at a temperature of 60 °F (15.5 °C). Therefore "80 proof" is 40% alcohol by volume, and pure alcohol is "200 proof".

29. What’s in a drink?

30. Legal BAC Levels
The alcohol level at which a person is considered to be legally impaired varies by country.
In the US the BAC limit is 0.08%
However, drivers of commercial vehicles have a limit of 0.04%
Sweden is one of the countries with the lowest level of 0.02%

31. When can you drink legally?
As of 2007, all U.S. states have a minimum purchase age of 21. Unlike the states, Puerto Rico, the U.S. Virgin Islands, and Guam have a minimum purchase age of 18.
In Mexico and Canada the drinking age is lower than 21, which encourages young people to go to these countries if they live near the border.

32. The brain of a six-week old baby with “Fetal Alcohol Syndrome”
Normal brain of six week old baby

33. Field Sobriety Testing
Horizontal Gaze Nystagmus
Walk and Turn Test
One Leg Stand Test

34. Horizontal gaze nystagmus

35. Horizontal gaze nystagmus
The officer attempts to estimate the angle at which the eye begins to jerk
"nystagmus" is medical jargon for a distinctive eye oscillation
if this occurs sooner than 45 degrees, it theoretically indicates a blood-alcohol concentration over .05%.
The smoothness of the eye's tracking the penlight (or finger or pencil) is also a factor, as is the type of jerking when the eye is as far to the side as it can go.

36. Walk and Turn

37. One leg stand

38. Collection and Preservation of Blood Evidence
Must be drawn aseptically under medically accepted conditions
An anticoagulant such as EDTA or potassium oxalate is added – to prevent clotting
A preservative such as sodium fluoride is added to prevent bacterial growth
Stored in refrigerator
Tested at a lab or medical facility

39. Other toxins in blood Narcotics (Heroine)
Non-narcotic substances (Cocaine)
Carbon Monoxide (CO)
Heavy metals such as lead, mercury, arsenic, etc.

40. ACID vs. BASE Drugs
Barbiturates and Aspirin (Acetylsalicylic acid) are acidic drugs with pHs lower than 7.
Phencyclidine (PCP), Methadone, Amphetamines and Cocaine are basic drugs with pHs higher than 7.

41. Carbon Monoxide
CO is a by product of combustion of organic materials (Gas, fires, etc.)
CO has a greater affinity to hemoglobin than does CO2 or O2.
CO + hemoglobin = carboxyhemoglobin
So once it is inhaled an enters the bloodstream, it competes with O2 for hemoglobin.
Too much CO kills – death by asphyxiation

42. The fate of other drugs in the bloodstream
Heroin – gets converted into morphine once in the bloodstream

43. THE END