Forensic Toxicology: Alcohol Overview

What is Alcohol?

• Alcohol is a liquid produced from the fermentation of various items.
• It is the most abused drug in America.
• In large quantities, it is toxic to the Central Nervous System.
• Acts primarily as a depressant, impacting cognitive functions:
  • Slows down cognitive processing.
  • Increases response time.
  • Decreases judgment.

Blood Alcohol Content (BAC)

• Alcohol is detectable in the bloodstream within minutes of consumption.
• Full absorption may take up to 90 minutes after finishing drinking.
• Up to 90% of consumed alcohol is processed by the body, mainly through the liver.
• About 5% is excreted unchanged via breath, sweat, and urine.

Rate of Absorption

• Factors affecting alcohol absorption:
  • Quantity of alcohol consumed.
  • Duration over which it was consumed.
  • Alcohol content of the beverage.
  • Presence of food in the stomach before drinking (and the type of food).
  • The weight and body type of the drinker.

Understanding BAC

• BAC is expressed as a percentage (weight per volume of blood).
• Example: "Her BAC at the time of arrest was 0.13."
  • Influenced by:
  • Weight of the individual.
  • Alcohol content of drinks.
  • Number of drinks consumed.
  • Time elapsed between consuming drinks.

Definition of a Standard Drink

• A drink is defined as:
  • 12 oz of beer.
  • 5 oz of wine.
  • 2 oz of liquor.

How Many Drinks Have You Had?

• Example:
  • 3 - 12 oz beers.
  • 2 - 12 oz beers and a full solo cup of wine.
  • 2 - 1 oz shots of whiskey and half a full solo cup of beer.

Processing Alcohol

• Generally, the body processes alcohol at a rate of $0.015$% BAC per hour, averaging about 1 drink per hour.
• Formula for determining expected BAC:
  • For Males: 0.071 imes ( ext{# oz of alcohol}) imes ( ext{% of alcoholic drink}) / ext{Body weight (lbs)}
  • For Females: 0.085 imes ( ext{# oz of alcohol}) imes ( ext{% of alcoholic drink}) / ext{Body weight (lbs)}

BAC Effects on the Body

• BAC ranges and associated effects:
  • $0.02 - 0.03$: Mildly relaxed, talkative.
  • $0.04 - 0.05$: Definite relaxation, slight impairment.
  • $0.06 - 0.07$: Judgment and safe driving impaired.
  • $0.08$: Judgment impaired, mood swings.
  • $0.09 - 0.10$: Loss of inhibition, impaired reaction times.
  • $0.11 - 0.13$: Possible vomiting, memory impairment.
  • $0.14 - 0.15$: Staggering, irrational behavior.
  • $0.16 - 0.3$: Extreme drunkenness, potential loss of consciousness.
  • Greater than $0.3$: Possible coma, risk of death exceeds $0.45$.

Example Calculations

• Tim's Scenario: 4 shots of tequila (40% alcohol) consumed in 1 hour.

  • Calculation: $0.071 imes 8 imes 40 / 220 = 0.10$
  • Expected effects: Loss of inhibition, impaired control.

• Sheila's Scenario: 18 oz ribeye and shared 25 oz bottle of wine (18% alcohol) over 3 hours.

  • Calculation: $0.085 imes 12.5 imes 18 / 160 = 0.12$
  • Adjusting for burn-off: $0.12 - (0.015 imes 3) = 0.075$
  • Advice: Should consider sobriety for driving.

Measurement of BAC

• Approx. 5% of alcohol leaves the body unchanged; breathalyzers measure breath alcohol.
• Henry's law relates breath and blood alcohol concentrations (1 ml of blood = 2,100 ml of expelled air).

Breathalyzer Test

• Breathalyzers measure alcohol content from air exhaled from the lungs.
• Reflect changes in blood alcohol via light transmission analyzes: more alcohol, less light.

Other Tests for Sobriety

• HGN Test: Tracking movement of a pen, indicating potential impairment at 0.10 BAC.
• WAT Test: Walk and turn, requiring simultaneous instruction execution.
• OLS Test: One-leg stand, assesses balance and cognitive function.
• Importance: These tests verify cognitive function which declines with alcohol impairment.

Final Notes

• Dangers of driving under influence are profound; cognitive impairment can lead to serious consequences regardless of perceived sobriety.