Forensic Applications and Criminology - Applied Toxicology Study Notes

FORENSIC TOXICOLOGY DEFINITION

• Definition: Forensic toxicology involves the application of toxicology to the purposes of the law.

• Primary Application: The most common use is identifying any chemical that may serve as a causative agent in inflicting death or injury on humans, or causing damage to property.

• Scientific Basis: It is described as a thoroughly modern science based on published and widely accepted scientific methods.

• Scope: It encompasses both the analysis of drugs in biological materials and the interpretation of those analytical results.

THE CONTROLLED SUBSTANCES ACT (CSA)

• Overview: The CSA is a statute establishing a federal policy to regulate the manufacturing, distributing, importing, exporting, and using of regulated substances.

• Legal Context: It was signed into law by President Richard Nixon in 1970. It serves as a network of laws that forensic toxicologists use to help identify legal violations.

• Classification System: The act consists of 5 categories, known as schedules, based on three criteria:

  1. Potential for abuse.

  2. Potential for legitimate medical use.

  3. Safety or dependence liability.

CSA Schedules and Examples

• Schedule I:

  • Characteristics: High potential for abuse; lack of accepted safety even for medical use.

  • Examples: Heroin, Lysergic acid ($LSD$), Marijuana, Gamma hydroxybutyric acid ($GHB$).

• Schedule II:

  • Characteristics: High potential for abuse; accepted medical use; may lead to severe psychological or physical dependence.

  • Examples: Morphine, Cocaine, Methadone, Hydrocodone, Fentanyl, Methamphetamine.

• Schedule III:

  • Characteristics: Less potential for abuse than I or II; accepted medical use; potential for moderate or low physical dependence or high psychological dependence.

  • Examples: Anabolic steroids (noted in text as having no abuse potential), Codeine and hydrocodone products (when mixed with aspirin or Tylenol).

• Schedule IV:

  • Characteristics: Even lower potential for abuse/dependence compared to Schedule III; leads to limited physical or psychological dependence.

  • Examples: Alprazolam, Clonazepam, Diazepam.

MEDICO-LEGAL ASPECTS OF POISONING

• Classification of Cases: Virtually every poisoning case (acute or chronic) has medico-legal overtones, categorized as:

  1. Accidental.

  2. Suicidal.

  3. Homicidal (noted as quite rare; the majority are accidental or suicidal).

• Legal Obligations of Hospitals: Every hospital (governmental or private) is legally obligated to treat a victim to the best possible extent. A case cannot be turned away because the hospital is not "authorized" for medico-legal cases.

• Primary Duty: The first and foremost duty is to save the patient's life by exercising reasonable skill and care.

• Duties of a Doctor in Suspected Poisoning:

  1. Medical Duty: Direct care and treatment of the patient.

  2. Medico-legal Duty: Proper documentation and preservation of samples to assist investigating agencies.

THE NARCOTIC DRUGS AND PSYCHOTROPIC SUBSTANCES ACT

• Legal vs. Medical Definitions: The term "narcotic" differs legally from its medical definition.

  • Legal Narcotics: Classified as True Narcotics (Opiates), Non-narcotic cannabis, and the Antithesis of a narcotic (Stimulants like Cocaine).

  • Psychotropic Substances: Mind-altering drugs including $LSD$, phencyclidine, amphetamines, barbiturates ($BAR$), and benzodiazepines ($BZD$).

• Prohibitions: The act imposes a complete prohibition on the cultivation of coca, poppy, and cannabis plants, as well as the manufacture, sale, purchase, use, or transport of these substances except for medical or scientific purposes.

• Egyptian Policy: The Government of Egypt ($GOE$) does not encourage or facilitate illicit production or distribution. There are strict laws and harsh penalties for government officials involved in such activities.

FORENSIC TOXICOLOGY AND ALCOHOL USE

• Nature of Ethanol: An addictive Central Nervous System ($CNS$) depressant, hypnotic, and sedative with dose-related neurological effects.

• Mechanism of Action:

  • Enhances the effect of $GABA$ (inhibitory neurotransmitter).

  • Inhibits the action of glutamate (excitatory neurotransmitter) on the $NMDA$ receptor.

• Toxico-kinetics:

  • Absorption: Rapidly absorbed via the $GIT$. Approximately $20\%$ is absorbed from the stomach and $80\%$ from the intestine.

  • Delayed Stomach Emptying: Rate is slowed by the presence of food or drinking undiluted alcohol.

  • Pylorospasm: High concentrations or heavy drinking cause spastic closure of the valve between the stomach and intestine, keeping alcohol in the stomach for hours and causing nausea and vomiting.

  • Peak Concentration: Blood alcohol concentration ($BAC$) peaks in $30-90\,\text{min}$ after the last drink.

  • Distribution: Throughout body tissues except those low in water content (adipose tissue, bone, hair).

Alcohol Consumption in Females

• Metabolism: Females possess less Alcohol Dehydrogenase ($ADH$) enzyme in the stomach. This leads to more alcohol entering the bloodstream and higher liver stress even with lower consumption volumes. Contraception pills or menstrual cycle fluctuations (estrogen) can alter liver enzyme activity.

• Distribution: Females have less total body water than men. Because alcohol is water-soluble, it remains more concentrated (higher $BAC$) in females.

• Telescoping Effect: Females often start drinking later in life but progress more rapidly to alcohol dependence or Alcohol Use Disorder ($AUD$).

Acute Alcohol Poisoning and Symptoms

• Treatment:

  1. Airway protection and ventilatory support.

  2. Gastric lavage (Activated charcoal is ineffective).

  3. Flumazenil ($3\,\text{mg IV}$) may reverse ethanol-associated respiratory depression.

  4. Hemodialysis: Eliminates ethanol $3$ to $4$ times faster than liver metabolism.

• Symptoms of Drunkenness:

  • Alcohol Flush Reaction: Redness in the face caused by excessive capillary dilation and damage.

  • Eye Effects: Relaxation of iris muscles leads to dilated pupils; sluggish pupil reflexes delay constriction in response to light.

FORENSIC TOXICOLOGY AND CANNABIS

• Origin: Derived from the Indian hemp plant (Cannabis sativa).

• Active Principle: $\Delta^9$-tetrahydrocannabinol ($THC$), found in both male and female plants.

• Forms: Marijuana (dried flower tops) and Hash (dried resin).

• Therapeutic Uses: Stimulating appetite in $AIDS$ patients and reducing nausea/vomiting in cancer chemotherapy.

• Mechanism of Action:

  • Stimulates presynaptic cannabinoid receptors ($CB1$).

  • Inhibits $Ca^{2+}$ channels and activates $K^+$ channels.

  • Causes Dopamine ($DA$) release through presynaptic inhibition of $GABA$ neurons in the Ventral Tegmental Area ($VTA$).

• Toxico-kinetics: Smoking has immediate effects; ingestion is slow and unpredictable due to stomach acid instability. Peak effects occur in $10-30\,\text{min}$ and last $1$ to $4\,\text{hours}$.

• Acute Poisoning: Euphoria, temporal/spatial disorientation, intensification of sensations (sights/sounds), and altered perception. Flashback phenomena can occur.

• Treatment: Decontamination for ingestion; Benzodiazepines for acute psychotic reactions.

• Forensic/Social Issues: Interference with motor skills and judgment makes operating machinery dangerous. Studies suggest impaired growth in infants of mothers who used cannabis during pregnancy. Medicinal cannabis is not authorized in Egypt and is regulated by Law No. 182 of 1960.

FORENSIC TOXICOLOGY AND COCAINE

• Origin: Alkaloid from the leaves of Erythroxylon coca.

• Clinical Use: Local anesthetic and iris dilation in ophthalmology.

• Mechanism of Action: Blocks reuptake of $DA$, $NE$, and Serotonin by blocking the Dopamine Reuptake Transporter ($DAT$). This increases $DA$ concentration in the synapse of the nucleus accumbens.

• Forms:

  1. Cocaine Hydrochloride: Water-soluble salt; injected or snorted.

  2. Crack Cocaine: Free base produced by heating cocaine with an alkaline substance; smoked for rapid lung absorption.

• Toxico-kinetics:

  • Onset: $1-3\,\text{min}$ (insufflation); smoking is as rapid as $IV$ injection.

  • Metabolism: Broken down by liver esterases and plasma cholinesterase to Ecgonine Methyl Ester ($EME$).

  • Toxicity: Lower plasma cholinesterase levels (found in children or specific patients) increase the severity of toxicity.

• Symptoms:

  • Acute: Hyperthermia, tremors, convulsions, respiratory/mental depression, cardiac arrhythmia, coma.

  • Chronic: Strong cravings, fatigue, anhedonia, nosebleeds, dilated pupils.

• Detection:

  • Blood: Not clinically useful due to rapid degradation.

  • Urine: Benzoyl-ecgonine (major metabolite) detected for $48-72\,\text{hours}$.

  • Hair: analysis of $EME$ and benzoyl-ecgonine via $GC-MS$.

FORENSIC TOXICOLOGY AND OPIOIDS

• Origin: Opium is the dried extract of the unripe fruit capsule of the poppy plant (Papaver somniferum).

• Alkaloids: Includes Morphine and Codeine.

• Mechanism of Action: Agonists at \mu$ (mu), \delta$(delta), and$\kappa$(kappa) receptors. Binding to$\mu$ receptors on $GABA$ neurons in the $VTA$ inhibits them, stimulating $DA$ neurons and causing euphoria.

• Toxico-kinetics:

  • Bioavailability: Oral morphine is only $25\%$ due to high first-pass metabolism in the liver.

  • Metabolism: Conjugation with glucuronic acid produces Morphine-6-glucuronide (pharmacologically active).

  • Protein Binding: $34\%$ of morphine is protein-bound.

• Acute Poisoning:

  • Pathognomonic Triad: Coma, pinpoint pupils, and respiratory depression.

  • Treatment: Supportive measures and $IV$ Naloxone (opioid antagonist).

• Forensic Issues: Chronic parenteral abuse causes abscesses, transverse myelitis, anaphylaxis, $AIDS$, and arrhythmias.

FORENSIC CRIMINOLOGY

• Definition: The study of scientific principles applied to the investigation of crime, combining scientific and behavioral perspectives.

• Key Techniques: Evidence collection including fingerprints, $DNA$, bodily fluids, tire tracks, tool marks, and fibers.

• Sub-fields of Forensic Criminology:

  1. Crime Scene Investigation: Proper collection, documentation, and preservation.

  2. Forensic Biology: Study of $DNA$ and bodily fluids.

  3. Fingerprinting: Identification and comparison.

  4. Trace Evidence: Fibers, hair, tool marks.

  5. Forensic Toxicology: Study of poisons and drugs.

  6. Forensic Pathology: Study of death, cause, and manner.

  7. Forensic Psychiatry: Mental state of criminals.

  8. Digital Forensics: Investigation of crimes involving computers and digital devices.