week 4

Understanding key terms related to forensic toxicology.
Familiarity with the legal impairment levels for blood and breath alcohol in South Africa.
Comprehension of how alcohol is absorbed, transported, and eliminated in the body.
Recognition of important components of the human circulatory system.
Explanation of breath alcohol excretion via alveoli.
Understanding infrared and fuel-cell breath-testing devices for alcohol detection.
Awareness of commonly used field sobriety tests for assessing alcohol impairment.
Comparison of laboratory procedures for measuring blood alcohol concentration.
Knowledge of precautions for preserving blood for alcohol analysis.
Appreciation of the toxicologist's role in the criminal justice system.
Understanding of techniques for isolating and identifying drugs and poisons.
Discussions on the significance of drug presence in human tissues for impairment assessment.

Toxicology: Study of toxic effects of drugs and chemicals on biological systems.
- Definition of Poison: Any substance that produces harmful effects when introduced to a living organism.
Forensic Toxicology: Application of toxicology, analytical chemistry, pharmacology, and medicinal chemistry in cases with legal implications.
- Reports often utilized in trials.
- Detects medications and toxins in bodily fluids (serum, blood), tissues, and organs.
- Toxicologists may work in criminal laboratories, medical examiners' offices, and hospitals.

Focuses on alcohol measurement in cases involving criminal law violations.
Alcohol - ethyl alcohol: colorless liquid commonly consumed as a beverage.
- Considered a depressant affecting the central nervous system, particularly the cerebellum.
- Blood alcohol concentration directly correlates with brain alcohol concentration.

Absorption:
- Alcohol enters blood minutes after ingestion, increasing concentration from stomach and intestines.
- Maximum blood alcohol level attained post absorption.
- Absorption time varies:
  - Empty stomach: 30-90 minutes.
  - Full stomach: 2-4 hours.
- Beer absorbed slower than high-concentration spirits due to carbohydrate content.
Distribution:
- Alcohol disperses uniformly in body’s watery areas (approx. two-thirds of body volume).
- In deceased individuals, alternative fluids (brain, cerebrospinal fluid, vitreous humour) may be assessed if blood unavailable.
Elimination:
- Alcohol is mainly eliminated through oxidation in the liver, converted to acetic acid, then to carbon dioxide and water.
- Approx. 5% excreted unchanged in breath, urine, and sweat.
- Blood alcohol concentration (BAC) expressed as percentage weight per volume:
  $ext{BAC} = \frac{ ext{grams of alcohol}}{ ext{100 mL of blood}}$
- Average elimination rate: 0.015% per hour.
- Example: At 0.10% BAC, approximately 6.5 hours needed to reach 0.00%.
- Legal BAC limits: 0.08% for drivers in the US, equivalent to 80 mg/dL.

Alcohol in blood to breath ratio at 34°C is 1:2100.
Breath testers measure alcohol concentration based on infrared absorption:
- Alcohol in breath exposed to infrared radiation determining BAC.
Fuel cell detectors convert alcohol to electrical current.

Field sobriety tests assess physical intoxication and evidence test acceptance.
Common tests:
- Horizontal gaze nystagmus test.
- Walk-and-turn test.
- One-leg stand test.
Mobile breath testers (fuel cell-based) are typically not admissible in court.

Forensic toxicologists analyze bodily fluids/organs for drugs/poisons without extensive background details.
- rely on general screening techniques to narrow down substances.
Challenges include:
- Evaluating drugs at low concentration different from concentrated forms (pills/powders).
- Drugs are altered/metabolized in the body, complicating detection and identification.
- Determination of drug potency required.

Identification of abused drugs involves a two-step approach:
- Screening: Initial tests to detect probable substances.
- Confirmation: Definitive tests to validate presence.
- Gas Chromatography/Mass Spectrometry (GC/MS):
- Gas Chromatography separates samples into components.
- Mass Spectrometry creates a “fingerprint” for identification.
Drug testing commonly occurs in blood; urine testing gaining popularity in workplaces.

Detecting and identifying drugs leads to evaluations impacting physical state/performance.
Blood concentrations of certain drugs can indicate pharmacological effects on individuals, but urine concentrations are poor indicators for action or behavior influence.
Considerations such as age, fitness, and individual tolerance must be taken into account.

Drugs in blood embed in hair during growth, allowing history of drug use assessment.
Average hair growth rate: 1 cm/month; analysis of hair segments provides drug intake timeline.

Heavy metals (e.g., arsenic, mercury): Identified via extraction in hydrochloric solution.
Carbon Monoxide Poisoning: Binds to hemoglobin with 230x affinity compared to oxygen, forming carboxyhemoglobin to measure severity of poisoning.

The primary duties of a forensic toxicologist.
Requirements for suitable alcohol intoxication tests.
Factors influencing alcohol absorption rates.
Alcohol elimination processes and their testing implications.
Advantages of blood tests conducted shortly after drinking.
Historical significance of the first breath-testing device.
Differences between early devices and modern testing tools.
Fuel cell detector functioning principles.
Factors affecting breath tester accuracy.
Explanation of divided-attention tasks in field sobriety tests (including examples).
Understanding the horizontal gaze nystagmus test impact on blood-alcohol level assessment.
Substances in collected blood and preservation significance.
Value of collecting blood from multiple body sites for alcohol determination.
Legal intoxication limits for general and commercial drivers in the US.
Challenges faced by forensic toxicologists in drug identification.
Role of metabolism in complicating toxicological tasks.
Importance of follow-up confirmation tests after positive screening.
Identification of preferred confirmation test.
Measurement of carbon monoxide levels in determining victim's condition during fire incidents.
Relevance of individual drug use history in evaluating forensic toxicology findings.