Ch 10 Forensic Toxicology

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Ch 10 Forensic Toxicology

• Alcohol in the bloodstream.
• Human circulatory system.
• Alcohol excretion in the breath.
• Breathalyzer.
• Chemical equations.
• Infrared breath-testing device.
• Field sobriety tests.
• Alcohol concentration in blood.

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• Blood alcohol in your state.
• Significance of the implied consent law and the
  Schmerber v. California case to traffic
  enforcement.
• Acids and bases.
• Role of toxicologist in the criminal justice
  system.
• Techniques of isolating and identifying drugs and
  poisons.
• Finding a drug in human tissues and organs.

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• Collaboration between Drug Recognition Expert and
  Forensic Toxicologist in positive drug finding.

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• Absorption passage of alcohol across the wall
  of the stomach and small intestine into the blood
  stream
•  Oxidation the combination of oxygen with other
  substances to produce new products
•  Excretion elimination of alcohol from the body
  in an unchanged state alcohol is normally
  excreted in breath and urine

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• Artery a blood vessel that carries blood away
  from the heart
• Vein a blood vessel that transports blood
  toward the heart
• Capillary a tiny blood vessel across whose
  walls exchange of materials between the blood and
  the tissue takes place receives blood from
  arteries and carries it to veins

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• Alveoli small sacs in the lungs through whose
  walls air and other between the breath the breath
  and the blood
• Catalyst a substance that acceleration the rate
  of a chemical reaction but is not itself
  permanently changed by the reaction
• Fuel cell a detector in which chemical
  reactions are used to produce electricit

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• Anticoagulant a substance that prevents
  coagulation or clotting of the blood
• Preservative a substance that stops the growth
  of microorganisms in blood
• Metabolize transforming a chemical in the body
  to another chemical for the purpose of
  facilitating its elimination from the body
• Acid a compound capable of donating a hydrogen
  ion (H) to another compound

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• Base a compound capable of accepting a hydrogen
  ion (H)
• pH a symbol used to express the basicity or
  acidity of a substance. A pH of 7 is neutral
  lower values are acidic and higher values are
  basic

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Ch. 10 - Forensic Toxicology

• Alcohol

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What is Toxicology?

• Toxicological examinations involve the
  identification and often quantization of drugs
  toxic materials in the human body
• The role of the forensic toxicologist is limited
  to matters pertaining to violations of criminal
  law
• determination of the presence of alcohol in the
  body
• identification of substances causing unnatural
  death

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Toxicology of Alcohol

• The Fate of Alcohol in the Body

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Properties of Alcohol

• Alcohol is a general term for a family of organic
  compounds
• commonly encountered members include methanol,
  ethanol, isopropanol
• The term alcohol will be taken to mean ethanol
  (ethyl alcohol)

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Chemical Properties of Ethanol

• A clear volatile liquid
• Burns easily
• oxidizes easily
• Slight, characteristic odor
• Is very soluble in water
• miscible in all proportions

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Physiological Properties of Ethanol

• A central nervous system (CNS) depressant
• CNS is the bodily system which is most severely
  affected by alcohol
• The degree to which the CNS function is impaired
  is directly proportional to the concentration of
  alcohol in the blood

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What Does the Body Do With Alcohol?

• When an alcoholic beverage is swallowed, it is
  diluted by stomach juices quickly distributed
  throughout the body
• Alcohol does not require digestion before its
  absorption into the bloodstream
• some diffuses into bloodstream directly through
  the stomach wall
• remainder passes into the small intestine
• rapidly absorbed circulated

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Alcohol Absorption

• Alcohol is absorbed from all parts of the
  gastrointestinal tract largely by simple
  diffusion into the blood
• small intestine is the most efficient region for
  absorption because of its large surface area
• The rate of absorption varies according to the
  particular beverage the state of the consumers
  stomach

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Alcohol Absorption

• Fasting individual
• 20-25 of a dose of alcohol is absorbed from the
  stomach
• 75-80 is absorbed from the small intestine
• peak blood alcohol concentrations occur in
  0.5-2.0 hrs

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Alcohol Absorption

• Non-fasting individuals
• presence of food in stomach (especially fatty
  foods) delays absorption
• peak alcohol concentrations 1.0-6.0 hrs
• Alcohol ingested with carbonated beverages
• ordinarily absorbed more rapidly than straight
  alcohol

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Alcohol Distribution

• Alcohol has a high affinity for water
• Is diffused in the body in proportion to the
  water content of the various tissues organs
• greater concentration in blood brain
• lesser concentration in fat muscle

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Alcohol Distribution

• Absorbed alcohol is greatly diluted by the
  aqueous body fluids
• 1 oz. (29.57 mL) of 50 (100 proof) whiskey will
  be diluted in a man of average build, to a
  concentration 2 parts per 10,000 in the blood
  (0.02)

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Blood Alcohol concentration

• BAC is the amount of alcohol in the bloodstream
  measured in percentages
• BAC 0.10
• means a person has 1 part alcohol per 1,000 parts
  of blood in the body

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Elimination

• Liver eliminate 95 of the alcohol through
  metabolism
• oxidation via acetaldehyde acetic acid to
  carbon dioxide water
• Remainder of eliminated through excretion in
  breath, urine, sweat, feces, milk saliva
• Rule of Thumb
• 0.5 oz (15 mL) alcohol eliminated per hr

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Blood Alcohol Concentrations

• A set of probable average curves of BAC in an
  average-size man after rapid absorption of
  various amounts of alcohol
• Shows rate of BAC decline over time as a result
  of metabolism excretion

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Elimination

• Absorbed alcohol is passed through the liver by
  circulating blood
• ADH (alcohol dehydrogenase) converts the alcohol
  to acetaldehyde
• acetaldehyde is a highly toxic substance
• Aldehyde dehydrogenase converts acetaldehyde to
  acetate ion
• Acetate enters blood stream is ultimately
  oxidized to CO2

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Elimination

• Both enzymatic reactions require a co-enzyme,
  NAD, which accepts a hydrogen from the molecule
• The temporary depletion of NAD by the first step
  limits the rate at which alcohol can be
  metabolized

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• Curve a
• drinking 2 oz alcohol each hr for 4 hours
• BAC increase is cumulative because alcohol is
  consumed faster than it can be metabolized
• Curve b
• drinking 8 oz all at once

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Affect of Body Mass
One Hour of Drinking
Two Hours of Drinking
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BACs Affect Behavior
Alcohol in the bloodstream continually circulates
to the brain
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Some Alcohol Statistics

• half of traffic injuries involve alcohol
• 1/3 of fatally injured passengers pedestrians
  have elevated blood alcohol levels
• half of homicides involve alcohol
• 1/2 to 1/3 of suicides involve alcohol
• CDC estimates 30,000 unintentional injury deaths
  are directly attributable to alcohol

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Alcohol Driving
Relative Fatality Risk(drivers in a single
vehicle crash)
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Respiratory System

• Volatile chemicals dissolved in the blood will be
  brought to equilibrium with the air in the lungs
• fixed ratio between compound in breath blood

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Alcohol in Blood vs Breath

• The ratio of alcohol in blood to alcohol in
  alveoli air is 2100 to 1
• 1 mL of blood will contain about the same amount
  of alcohol as 2100 mL of breath
• During the period of absorption, the alcohol
  concentration is higher in arterial blood than
  venous blood
• breath test reflects alcohol conc. in the
  pulmonary artery (reflects what reaches the brain

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The Breathalyzer

• Measures the alcohol content of alveolar breath
• Subject blows into a mouthpiece until 52.5 mL of
  alveolar breath has been collected
• measures alcohol concentration of 1/40 mL of
  blood
• The alcohol in the blood is reacted with chromic
  acid

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Breathalyzer

• Beers Law
• the concentration of Cr (VI) is directly
  proportional to the amount of 420 nm light light
  absorbed by the sample
• Measures the concentration of the unknown
  solution to the concentration of a standard
  sample