Pharmacology and Toxicology Quiz

DNA Analysis

• Sir Alec Jeffreys (1985) developed VNTR analysis using RFLP.
• DNA evidence sources:
  • Blood (white blood cells)
  • Hair (nuclear DNA in root, mitochondrial DNA in shaft; medulla, cuticle, cortex)
  • Bone (osteocytes, osteoclasts, osteoblasts; compact bone)
  • Teeth (pulp)
  • Other cells (spermatozoa, vaginal cells, buccal cells)
• Extraction methods:
  • Cell and tissue disruption
  • Membrane and organelle lysis
  • Organic extraction (phenol:chloroform)
• Contamination control crucial.
• Storage methods: FTA® Cards, Chelex®.
• Semen: Differential lysis.
• Quantification:
  • PCR (denature, anneal, extension)
  • Real-time Q-PCR (measures DNA concentration based on amplicon amount)
  • Quantitative PCR (Q-PCR) uses TaqMan® method (reporter dye, quencher molecule; cleavage releases dye).

Forensic DNA Profiling

• Short Tandem Repeats (STRs):
  • Core repeat regions in 20 STR loci used in US forensic science.
  • STR naming example: D5S818 (chromosome #, locus number).
  • Repeat lengths (dimer to hexamer), with tetra- and pentameric repeats used most.
  • Allele designation based on repeat numbers (example: (AGAT)10 = allele 10).
  • Simple, compound, and complex repeats (example alleles for D5S818, D8S1179, D21S11).
• Multiplexing: fluorescent labels on amplicons, separated by capillary electrophoresis.
• Electropherogram and allelic ladder show homozygosity (one peak), heterozygosity (two peaks) at loci.
• Mixed samples pose challenges. Interpretation of STR profiling leads to inclusion, exclusion, or inconclusive results.

Combined DNA Index System (CODIS)

• Used for case-to-offender, case-to-case, familial, and international searches.
• Two indices: Forensic index (crime scenes), Offender index.
• Rapid DNA instruments speed up analysis.

Probability of Matching STR Profiles

• The product rule calculates the probability of a combined match (Pm) for multiple loci. Allele frequencies guide calculations.

Sex Typing

• Amelogenin (AMEL) loci distinguish male from female. (AMELX, AMELY).

Mitochondrial DNA Profiling

• mtDNA is maternally inherited.
• Forensics benefits: maternal inheritance, large amount of mtDNA, robustness.
• Forensics drawbacks: less resolution compared to nuclear DNA.

Strength of DNA Profiling

• Allele frequency (p): count of one allele type divided by total alleles at a locus. Table of frequencies available.
• Genotype frequency (P): Number of individuals with a given genotype / total individuals.
• Hardy-Weinberg principle: equilibrium allows prediction of genotype frequencies based on allele frequencies (p² for homozygotes, 2pq for heterozygotes, p² + 2pq + q² = 1).

Bloodstain Pattern Analysis

• Analyzing bloodstain characteristics (dispersion, shape, volume, pattern, number, relationship).
• First systematic studies by Eduard Piotrowski (1895).
• Compositions
  • 55% plasma; 45% formed elements (RBCs, WBCs, platelets).
• Three bloodstain types:
  • Passive (clots, drops, flows, pools)
  • Transfer (wipes, swipes, pattern transfers, contact)
  • Projected (spatters, splashes, cast-offs, arterial spurts)
• Spatter types: forward, back.
• Cast-offs: linear, reflect the motion of bloody objects.
• Arterial spurts: arc patterns indicate blood pressure.
• Miscellaneous (fly spots, voids, skeletonized stains).
• Measurements: angle of impact, direction angle, directionality, satellite droplets, point-of-origin.
• Visual enhancements: Luminol, LCV.
• Documentation of entire scene crucial.

Pharmacokinetics

• Absorption into bloodstream via various routes (oral, rectal, inhalation, IV, sublingual, transdermal, etc.)
• Gastrointestinal tract (GIT).
• First-pass effect/metabolism (drug reduction before systemic circulation).
• Bioavailability (proportion of drug reaching systemic circulation after oral vs IV).
• Distribution factors: tissue blood flow, drug-tissue partitioning, molecular size, protein binding.
• Metabolites = substances produced during metabolism (more or less active).
• Liver = major site of metabolism.
• Postmortem redistribution (uneven drug distribution after death; heart blood affected most, femoral or subclavian preferred).
• Half-life = time for drug concentration to decrease by 50%.

Drug Recognition Expert (DRE) Program

• Overview: IACP coordinates DEC program; NHTSA support.
• 12-step DRE process (details in links)
• 7 Drug categories (details in links)

Drugs of Abuse

• Drug definitions and seven DRE categories.
• Analogue drugs, "cousin" drugs.
• DEA Schedules (I-V) classify drugs based on abuse potential.
• Ethanol (CNS depressant); distribution in tissues with high water content; chronic consumption leads to liver damage (cirrhosis).
• CNS depressants (adverse effects: reduced pulse & blood pressure). Examples: barbiturates, benzodiazepines (Valium®, Xanax®).
• CNS stimulants (adverse effects: increased pulse & blood pressure; dilated pupils). Examples: amphetamines (methamphetamine), cocaine (crack), MDMA.
• Hallucinogens (adverse effects: synesthesia). Example: LSD.
• Dissociative anesthetics; adverse effects: "moon walking" Example: PCP.
• Narcotic analgesics (adverse effects: "on the nod" constricted pupils). Opioid = morphine-like. Opiate = naturally occuring/semi-synthetic from opium. Heroin (metabolizes to 6-monoacetylmorphine and then morphine), oxycodone/hydrocodone (Vicodin®), carfentanil.
• Inhalants (adverse effects: flushed face; examples: nitrous oxide, volatile solvents, aerosols)
• Cannabinoids (adverse effects: reddened eyes). Active drug: delta-9-tetrahydrocannabinol.

Forensic Toxicology

• Pharmacology (drug effects), Pharmacokinetics (drug movement), Pharmacodynamics (drug actions).
• Clinical vs. Forensic toxicology.
• Postmortem toxicology, Human Performance Toxicology (DUI), Workplace drug testing.
• Postmortem specimens (blood [2 sites], VH, urine, bile, tissues, gastric contents, other). Alternative samples (skeletal muscle, bone, hair, nails, maggots).
• Interpretation considers context, tested specimens, drug interactions, and postmortem redistribution.

Other Substances Encountered

• Volatile substances (inhalants; toluene, analysis by GC).
• Carbon monoxide (colorless, odorless, tasteless gas; high affinity for hemoglobin, analysis by measuring carboxyhemoglobin).
• Salicylates (aspirin, Bengay®, analysis by ELISA or GC/MS).
• Metals (Arsenic, Lead, Lithium, Mercury, Thallium; acute/chronic toxicity; analysis is challenging).
• Anions (cyanide, analysis by GC/MS or spectrophotometry).

Forensic Microbiology

• Emerging discipline analyzing biocrimes/bioterrorism. Definitions: biological warfare, bioterrorism, biocrime, epidemiology, forensic epidemiology, zoonoses.
• Case example: Anthrax attack (Bacillus anthracis, 2001).
• Microbial forensic tools: Nucleic acid-based methods (MLVNTR), cultures (gold standard).
• Preparedness: Anti-terrorist bill (1999), PulseNet, Bioterrorism Act (2002), Select Agents and Toxins List, plans.
• Laboratory biosafety levels.

Trace Evidence Analysis

• Locard's exchange principle: every contact leaves a trace.
• Comparative analysis of known (K) and questioned (Q) materials.
• Class vs. individual characteristics. Class characteristics are more useful when subsets are very small.
• Examples:
  • Fibers (natural/manufactured; color analysis, PLM).
  • Paints (binder, vehicle, solvent; microscopes; PGC; PDQ database).
  • Soil (organic humus and inorganic minerals; microscopes; HPLC).
  • Glass (physical fit, density, refractive index, microscopic analysis).

Analysis of Seized Drugs

• Components: Physical exam, sampling plans (using statistical tools like hypergeometric table).
• Screening tests: Marquis, Duquenois-Levine. Qualitative analysis: GC-MS, microscopic (e.g., marijuana cystolithic hairs)
• Using references such as PDR.