Forensic Toxicology—Postmortem & Human Performance (copy)

Postmortem Toxicology - Definition & Scope

• Investigation of drugs, gases, metals, or other toxic chemicals in a decedent to determine contribution to death.

• Contrasted with human-performance toxicology (living subjects, performance/behavior). ### Case History Gathering - Elements collected before laboratory work:

• Age, sex, weight, medical history.

• Medications administered pre-mortem.

• Autopsy findings.

• Drugs available to the deceased.

• Time interval between onset of symptoms and death.

• Scene investigation to tentatively identify possible toxins. ### Specimen Collection During Autopsy - Drugs concentrate differently; multiple organs/fluids collected:

• Brain – 50\;g

• Liver – 50\;g

• Kidney – 50\;g

• Heart (central) blood – 25\;mL

• Peripheral blood – 10\;mL

• Vitreous humor, bile, urine, gastric contents – all available amounts. - Labeling: date/time, name, specimen type, case #, pathologist’s signature. - Collect before embalming; embalming fluid (alcohols) can confound results. ### Special Situations & Alternative Matrices - Exhumed/burned bodies → bone marrow, vitreous humor, hair, or maggots. - Vitreous humor resists putrefaction → slower chemical decay. - Hair segments document chronic/temporal exposure (e.g., arsenic timeline using growth rate 12.5\;mm\,/\,month). ### Analytical Strategy 1. Prioritize specimens by likely concentration pathway:

• Oral intake → analyze gastric contents first, then urine (major excretion route), then liver. 2. Metabolite knowledge: FDA & DEA libraries allow ID of prescription/abuse-drug metabolites. 3. Stable poisons (Hg, As, barbiturates) detectable years later. #### Screening vs. Confirmation - Presumptive/Immunoassay tests → opiates, barbiturates, drug classes. - GC-MS confirmation

• GC separates by volatility/polarity; MS provides fragment spectra.

• Library > 10^5 reference spectra; software matches unknown peaks. #### Inorganic/Metal Analysis - ICP-OES screens up to \approx20 metals (Hg, As, Tl, etc.) simultaneously. ### Interpretation of Results - Determine: route, dose, lethality. - Highest concentration indicates entry site (GI → oral, lungs → inhalation, localized tissue → injection). - Medical interventions (transfusions, diuretics) dilute evidence. - Dose estimation:

• For each organ: \text{conc}*i\times\text{mass}*i → sum = minimal administered dose. - Time-of-administration (hair): segmental analysis correlates spikes with suspect’s access times. - Heart vs. peripheral blood: postmortem redistribution ↑ heart-blood drug levels over time. ## Human-Performance Toxicology - Measures alcohol/drugs in living persons to assess behavioral impairment (e.g., DUI/DUID). ### Field Sobriety Testing (FST) - Presumptive battery before chemical BAC test:

• Interview & structured questions.

• Horizontal gaze nystagmus, eye convergence.

• Divided-attention psychophysical tasks: walk-and-turn, one-leg stand, Romberg balance, finger-to-nose.

• Vital signs, dark-room pupil exam, muscle rigidity, injection-site check.

• Breath/urine screening. - Failure → breath or blood confirmation. ### BAC Levels & Physiological Effects - \le 0.06\% → considered sober. - 0.08\% (legal U.S. per-se limit since 2003) → impaired. - 0.18\% → confusion. - 0.27\% → stupor. - 0.35\% → coma. - USA fatal-crash data (2002): 17{,}000 deaths, 41\% of traffic fatalities. ### Legal Evolution - 1939 Indiana: first BAC-based statute. - 1964 Grand Rapids Study (17,000 controls; 3,300 crash drivers):

• Quantified crash-risk vs. BAC; >0.04\% ↑ risk.

• Founded per-se laws (BAC alone = intoxication).

• Validated breathalyzer. - Implied-consent laws (by 1973 all states): refuse test → license loss 6{-}12 months. - Advocacy (MADD, 1980) → harsher penalties; DUI fatalities fell from 60\% → 43\% (1980-1993). - Federal 0.08\% mandate, 2000; 0.04\% for commercial drivers. - International limits: Canada/UK/Italy 0.08\%; Australia 0.05\%; Sweden 0.02\%. ## Alcohol Pharmacokinetics ### Absorption - Oral route: mouth → esophagus → stomach → small intestine. - Absorbed \approx20\% in stomach, \approx80\% in small intestine. - Influencing factors:

• Gastric emptying rate.

• Food presence (delays emptying 1.5{-}2\;h).

• Concentration & beverage type.

• Drinking rate (drinks/hour).

• Exercise or GI-active drugs (nicotine, marijuana, ginseng) slow absorption. - Experimental data:

• 0.8\;g/kg on empty stomach → faster/higher peak BAC.

• One drink/hr for 8 h never >0.05\%; two drinks/hr → 0.18\% in 5 h. ### Distribution - Alcohol partitions with body water; tissues equilibrate quickly with blood. - Water-rich organs show higher concentrations. ### Elimination - Oxidation in liver: alcohol → acetaldehyde → acetic acid → CO*2 + H*2O. - >90\% metabolized; remainder excreted in sweat, urine, breath (basis for breath tests). - Chronic intake ↑ liver enzymes → testosterone oxidation → alcoholic impotence. - Competitive treatment: IV ethanol for methanol/ethylene-glycol poisoning (slows toxic metabolite formation). ## Estimating & Measuring BAC ### Back-Extrapolation - After absorption ends:

\text{BAC}*{\text{accident}} = \text{BAC}*{\text{sample}} + (k \times \Delta t)

• k = elimination rate 12.5{-}25\;mg/100\;mL\;h (avg 18.7).

• \Delta t = hours between incident and sampling. ### Direct vs. Indirect Measurement - Blood analysis (GC) = gold standard; must draw under medical conditions. - Breath analysis (portable, immediate) converts breath alcohol via Henry’s law:

• At 34\;^{\circ}C, 1\;mL blood ⇔ 2100\;mL alveolar breath (ratio 2100{:}1). ## Breath-Testing Technologies ### Breathalyzer (1954) - Chemistry: 2\;K*2Cr*2O*7 + 3\;C*2H*5OH + 8\;H*2SO*4 \rightarrow 2\;Cr*2(SO*4)*3 + 3\;CH*3COOH + 11\;H*2O - Color change (orange → green) measured photometrically at \lambda = 420\;nm. - Beer's law: A = Kc (absorbance ∝ alcohol conc.). - Requires fresh reagents; chemical consumption a limitation. ### Intoxilizer (IR Spectroscopy) - Deep-lung sample ensured by spring-valve. - IR lamp → sample cell → wavelength filters (exclude acetone, toluene, acetaldehyde). - Detector converts IR absorbance to BAC; no chemical reagents consumed. ### Alco-Sensor (Fuel Cell) - Pt-coated acidic fuel cell; reaction:

C*2H*5OH + H*2O \rightarrow CH*3COOH + 4H^+ + 4e^- (anode)

O*2 + 4H^+ + 4e^- \rightarrow 2H*2O (cathode) - Electron flow ∝ oxidized alcohol amount; microprocessor outputs BAC. ## Blood Collection & GC Analysis ### Sampling & Preservation - Skin disinfected with non-alcoholic antiseptic. - Collected into sealed vial containing:

• Anticoagulant (EDTA or K₂

Postmortem Toxicology - Definition & Scope

• Investigation of drugs, gases, metals, or other toxic chemicals in a decedent to determine contribution to death.

• Contrasted with human-performance toxicology (living subjects, performance/behavior). ### Case History Gathering - Elements collected before laboratory work:

• Age, sex, weight, medical history.

• Medications administered pre-mortem.

• Autopsy findings.

• Drugs available to the deceased.

• Time interval between onset of symptoms and death.

• Scene investigation to tentatively identify possible toxins. ### Specimen Collection During Autopsy - Drugs concentrate differently; multiple organs/fluids collected:

• Brain – 50\;g

• Liver – 50\;g

• Kidney – 50\;g

• Heart (central) blood – 25\;mL

• Peripheral blood – 10\;mL

• Vitreous humor, bile, urine, gastric contents – all available amounts. - Labeling: date/time, name, specimen type, case #, pathologist’s signature. - Collect before embalming; embalming fluid (alcohols) can confound results. ### Special Situations & Alternative Matrices - Exhumed/burned bodies → bone marrow, vitreous humor, hair, or maggots. - Vitreous humor resists putrefaction → slower chemical decay. - Hair segments document chronic/temporal exposure (e.g., arsenic timeline using growth rate 12.5\;mm\,/\;month). ### Analytical Strategy 1. Prioritize specimens by likely concentration pathway:

• Oral intake → analyze gastric contents first, then urine (major excretion route), then liver. 2. Metabolite knowledge: FDA & DEA libraries allow ID of prescription/abuse-drug metabolites. 3. Stable poisons (Hg, As, barbiturates) detectable years later. #### Screening vs. Confirmation - Presumptive/Immunoassay tests → opiates, barbiturates, drug classes. - GC-MS confirmation

• GC separates by volatility/polarity; MS provides fragment spectra.

• Library > 10^5 reference spectra; software matches unknown peaks. #### Inorganic/Metal Analysis - ICP-OES screens up to \approx20 metals (Hg, As, Tl, etc.) simultaneously. ### Interpretation of Results - Determine: route, dose, lethality. - Highest concentration indicates entry site (GI → oral, lungs → inhalation, localized tissue → injection). - Medical interventions (transfusions, diuretics) dilute evidence. - Dose estimation:

• For each organ: \text{conc}\i\times\text{mass}\i → sum = minimal administered dose. - Time-of-administration (hair): segmental analysis correlates spikes with suspect’s access times. - Heart vs. peripheral blood: postmortem redistribution ↑ heart-blood drug levels over time. ## Human-Performance Toxicology - Measures alcohol/drugs in living persons to assess behavioral impairment (e.g., DUI/DUID). ### Field Sobriety Testing (FST) - Presumptive battery before chemical BAC test:

• Interview & structured questions.

• Horizontal gaze nystagmus, eye convergence.

• Divided-attention psychophysical tasks: walk-and-turn, one-leg stand, Romberg balance, finger-to-nose.

• Vital signs, dark-room pupil exam, muscle rigidity, injection-site check.

• Breath/urine screening. - Failure → breath or blood confirmation. ### BAC Levels & Physiological Effects - \le 0.06\% → considered sober. - 0.08\% (legal U.S. per-se limit since 2003) → impaired. - 0.18\% → confusion. - 0.27\% → stupor. - 0.35\% → coma. - USA fatal-crash data (2002): 17{,}000 deaths, 41\% of traffic fatalities. ### Legal Evolution - 1939 Indiana: first BAC-based statute. - 1964 Grand Rapids Study (17,000 controls; 3,300 crash drivers):

• Quantified crash-risk vs. BAC; >0.04\% ↑ risk.

• Founded per-se laws (BAC alone = intoxication).

• Validated breathalyzer. - Implied-consent laws (by 1973 all states): refuse test → license loss 6{-}12 months. - Advocacy (MADD, 1980) → harsher penalties; DUI fatalities fell from 60\% → 43\% (1980-1993). - Federal 0.08\% mandate, 2000; 0.04\% for commercial drivers. - International limits: Canada/UK/Italy 0.08\%; Australia 0.05\%; Sweden 0.02\%. ## Alcohol Pharmacokinetics ### Absorption - Oral route: mouth → esophagus → stomach → small intestine. - Absorbed \approx20\% in stomach, \approx80\% in small intestine. - Influencing factors:

• Gastric emptying rate.

• Food presence (delays emptying 1.5{-}2\;h).

• Concentration & beverage type.

• Drinking rate (drinks/hour).

• Exercise or GI-active drugs (nicotine, marijuana, ginseng) slow absorption. - Experimental data:

• 0.8\;g/kg on empty stomach → faster/higher peak BAC.

• One drink/hr for 8 h never >0.05\%; two drinks/hr → 0.18\% in 5 h. ### Distribution - Alcohol partitions with body water; tissues equilibrate quickly with blood. - Water-rich organs show higher concentrations. ### Elimination - Oxidation in liver: alcohol → acetaldehyde → acetic acid → CO\2 + H\2O. - >90\% metabolized; remainder excreted in sweat, urine, breath (basis for breath tests). - Chronic intake ↑ liver enzymes → testosterone oxidation → alcoholic impotence. - Competitive treatment: IV ethanol for methanol/ethylene-glycol poisoning (slows toxic metabolite formation). ## Estimating & Measuring BAC ### Back-Extrapolation - After absorption ends:

\text{BAC}\{\text{accident}} = \text{BAC}\{\text{sample}} + (k \times \Delta t)

• k = elimination rate 12.5{-}25\;mg/100\;mL\;h (avg 18.7).

• \Delta t = hours between incident and sampling. ### Direct vs. Indirect Measurement - Blood analysis (GC) = gold standard; must draw under medical conditions. - Breath analysis (portable, immediate) converts breath alcohol via Henry’s law:

• At 34\;^{\circ}C, 1\;mL blood ⇔ 2100\;mL alveolar breath (ratio 2100{:}1). ## Breath-Testing Technologies ### Breathalyzer (1954) - Chemistry: 2\;K\2Cr\2O\7 + 3\;C\2H\5OH + 8\;H\2SO\4 \rightarrow 2\;Cr\2(SO\4)\3 + 3\;CH\3COOH + 11\;H\2O - Color change (orange → green) measured photometrically at \lambda = 420\;nm. - Beer's law: A = Kc (absorbance ∝ alcohol conc.). - Requires fresh reagents; chemical consumption a limitation. ### Intoxilizer (IR Spectroscopy) - Deep-lung sample ensured by spring-valve. - IR lamp → sample cell → wavelength filters (exclude acetone, toluene, acetaldehyde). - Detector converts IR absorbance to BAC; no chemical reagents consumed. ### Alco-Sensor (Fuel Cell) - Pt-coated acidic fuel cell; reaction:

C\2H\5OH + H\2O \rightarrow CH\3COOH + 4H^+ + 4e^- (anode)

O\2 + 4H^+ + 4e^- \rightarrow 2H\2O (cathode) - Electron flow ∝ oxidized alcohol amount; microprocessor outputs BAC. ## Blood Collection & GC Analysis ### Sampling & Preservation - Skin disinfected with non-alcoholic antiseptic. - Collected into sealed vial containing:

• Anticoagulant (EDTA or K₂Oxalate) — prevents clotting.

• Preservative (e.g., sodium fluoride) — inhibits microbial growth and prevents glucose metabolism.