#8 - alcohol

Forensic Toxicology

  • Definition:

    • Detects and identifies drugs and poisons in body fluids, tissues, and organs.

  • Work environments:

    • Crime laboratories, medical examiners’ offices, hospital labs, health facilities.

  • Key fact:

    • Ethyl alcohol, a legal substance, is the most abused drug in Western countries.

Toxicology of Alcohol

  • Main focus:

    • Measurement of alcohol for criminal law issues.

  • Importance:

    • Detection and isolation of drugs for behavioral influence assessment.

  • Characteristics of Alcohol:

    • Colorless liquid, diluted with water, widely consumed.

    • Major factor in traffic deaths.

    • Depressant affecting the central nervous system (CNS).

    • Blood alcohol concentration correlates with brain alcohol levels.

Alcohol in the Body

Absorption

  • Process:

    • Alcohol enters blood minutes after consumption, peaks 30-90 minutes post-drinking.

    • Rate affected by:

      • Stomach contents (empty/full affects absorption time).

      • Beverage type (beer vs. distilled spirits).

  • Uniform distribution through body fluids after absorption.

Distribution

  • Alcohol spreads evenly across all watery body compartments (approx. 2/3 of body volume).

Elimination

  • Theetholysis through oxidation in the liver:

    • Alcohol converted to acetic acid, then to carbon dioxide and water.

  • Excretion:

    • 5% of alcohol unchanged via breath, urine, perspiration.

    • Average elimination rate is 0.015% per hour, affecting time to return to zero.

Blood Alcohol Concentration (BAC)

  • Definition:

    • Measurement of alcohol in blood (% weight per volume).

  • Legal limit in U.S.: 0.08%.

  • BAC's impact on driving ability:

    • Elevated risks at varying BAC levels.

    • Connection to impairment symptoms.

Alcohol and the Circulatory System

  • Summary of interaction:

    • Alcohol absorbed into bloodstream from stomach/intestines, carried to the liver, affects breathing and heart rate.

  • Diagram representation of human circulatory system:

    • Oxygenated vs. deoxygenated blood pathways.

Alcohol’s Effect on Youth

  • Statistics:

    • Approx. 11 million U.S. youth under 21 consume alcohol.

    • High binge-drinking rates and associated risks (teen crashes, suicides, assaults).

    • Early experimentation with alcohol (boys at age 11, girls at 13).

Biological Impact of Alcohol

  • Brain impact:

    • Depressant effects on judgment, coordination, basic survival functions depending on BAC.

  • Sex disparities:

    • Women metabolize alcohol differently, less muscle (more fat) affects dilution; lack of protective stomach enzymes leads to higher BAC.

Alcohol Metabolism

  • Three major elimination methods:

    • Kidneys (5% urine), lungs (5% breath), liver (oxidation).

  • Breakdown process entails ethanol conversion to acetaldehyde and then to acetic acid in the presence of oxygen.

Alcohol Detection Methods

Gas Chromatography

  • Commonly used method for determining blood alcohol levels in forensic labs.

  • Auto analyzers in clinical settings measure alcohol levels as serum alcohol.

Breath Testing

  • Breath analysis shows alcohol concentration based on blood alcohol levels.

  • Ratio: 2,100 ml alveolar air = 1 ml blood.

  • Breathalyzers (Breathalyzer and Intoxilyzer) utilize infrared light absorption for BAC measurement.

Legal Aspects of Alcohol Testing

  • Accuracy and calibration are crucial for the use of results in DWI trials.

  • Portable breath testing devices provide preliminary measures but are not admissible in court.

Understanding Alcohol Chemistry

  • Molecular structure of ethanol (C2H5OH) involves distinctive bonding crucial for detection.

  • Infrared spectroscopy identifies ethanol based on specific molecular vibrations.

Conclusion

  • Forensic toxicologists face diverse challenges when analyzing drugs and poisons, necessitating a thorough understanding of both biological and chemical properties of substances like alcohol.