Forensic Toxicology

Forensic Toxicology

Identification and quantitation of drugs, poisons, or toxins in medicolegal cases

Applications of Forensic Toxicology

• Medical Examinations

• DUID/DUIs

• Workplace drug testing

• Drug-facilitated crimes (DFC) like sexual assault

Forensic Toxicologist requirements

• Know about drug metabolism, distribution, and excretion

• Use analytical instruments

• Understand legal meaning of impairment

• Know statutes/regulation

• Translate knowledge to examiners, coroners, LEOs

What is the top cause of overdose deaths?

Fentanyl

Wine is produced with…

Grapes

Beer is produced with…

Barley/wheat/hops

Bourbon is produced with…

Corn

Scotch is produced with…

Malt barley

Vodka is produced with…

Potatoes

Rum is produced with…

Molasses

NYS Vehicle and Traffic Safety Law

Article 31, 1192 and 1194 defines impairment while driving and administration of chemical tests during investigation

Article 31, 1194

Governs the administration of chemical tests when someone is suspected of driving under the influence

Implied consent

Any person driving a vehicle has given consent to chemical testing if lawfully arrested

When should chemical tests be administered?

Within 2 hours of arrest

Driving While Ability Impaired

Blood alcohol more than .05% but less than .08%

Evidence needed for Driving While Ability Impaired

• Chemical test

• Field sobriety test

• Officer observations

Driving While Intoxicated

Blood alcohol of .08 or higher (0.04 for commercial drivers)

Common Law DWI

Driving while intoxicated even without BAC, based on observed impairment

Zero Tolerance laws

Commercial drivers and drivers under 21

BAC above 0.18

Incurs enhanced penalty higher than DWI

Alcohol Absorption

Mainly in the small intestine but also the stomach

Absorption rate depends on…

• Amount consumed

• Time consumed

• Food in stomach

Peak BAC

Occurs 30 to 90 minutes after last drink

Where does alcohol get distributed to?

Watery portions of the body

Elimination mechanisms

• Oxidation (95%)

• Excretion

Oxidation of alcohol

• Occurs in liver

• Alcohol dehydrogenase: ETOH → Acetaldehyde

• Aldehyde dehydrogenase: acetic acid

• Acetic acid is oxidized to CO2 and water

Excretion of alcohol

2-5% is excreted in the urine, breath, and perspiration

Amount exhaled is directly proportional to blood content

Rate of elimination for alcohol

.015% per hour

Types of breath testing technology

1. Infrared spectrophotometry

2. Fuel-cell based

Infrared Spectrophotometry Breath Test

Intoxilyzer 9000, measuring specific IR absorption by ethanol, specificity

MOST common

Fuel-Cell Based Breath Test

Portable devices with platinum-based oxidation reactions used for screening

Evidence sources for impairment

• Analytical (quantitative) results

• Field Sobriety Tests

• Drug Recognition Expert evaluation

• Officer observations

Limitations to quantitative tests

• Poor correlation between blood concentration and impairment for drugs

• Individual variability in effects

Drug Recognition Expert (DRE)

Officer trained to recognize drug impairment and determine likely drug family based on eyes, vitals, and psychophysical tests

Headspace GC Analysis

• GC with 2 columns for separating alcohols

• Blood is collected and analyzed for the concentration of ethanol

  • By direct injection of serum or injection of headspace after equilibriating

Analysis of drugs in blood

• First, screen with urine sample and if positive, blood is analyzed

  • Minimized unnecessary blood draws

• Most drugs are excreted in urine

Screening Tests

Immunoassay screens for drug class

Good screening test

Immunoassay

Confirmatory Tests

• Definitively identifies drug with high specificity and sensitivity

• Can be used in court as evidence

• Slower and more expensive (run in batches)

Gold standard for drug confirmation

LC-MS/MS

GC-MS for confirmation

Stable, robust, and reproducible analysis with a more dynamic range than LC-MS/MS

Run in SIM (selective ion monitoring mode)

SIM Mode

Instead of detecting all fragments, only specific ions are detected

Loss in specificity but increase sensitivity

LC-MS/MS

Superior to GC/MS (sensitivity and specificity), less sample volume, less stability concerns, and can analyze many drugs simultaneously

Does presence = impairment?

No, drugs can stay in the system for days to weeks without causing effects, individuals vary (tolerances)

Multiple lines of evidence required

Blank sample

Sample without analyte used before each analysis to verify no contamination in the instrument that would result in false positives

Certified reference material

Controls used to check quality and accuracy of lab tests

False Positive

Test says drug is present even if none is

Marijuana DUI

Screen urine/blood for major metabolite of THC using SIM mode

MUST identify active THC

Cocaine detection

Found in urine if shortly after consumption (benzoylecgonine), then confirmed in blood

Cocaine in blood = recent ingestion

High levels if CRACK was smoked

Types of cocaine abuse

1. Intranasal (snorting) - 2-3 minute onset lasting 30-45 min

2. IV - 30-45 sec onset lasting 10-20 min

3. Smoking (CRACK) - 8-10 sec onset lasting 5-10 min

Heroin Metabolized

1. Diacetylmorphine hydrolyzed to 6-monoacetylmorphine

2. Hydrolyzed to morphine

3. Demethylation to normorphine

GHB

• Precursor and catabolic metabolite of neurotransmitter GABA

• Easily made with GBL and NaOH

  • Another precursor = 1,4-butandiol and pine needle oil

GHB Appearance

White powder, dissolved in water colorless, odorless, tasteless

GHB Effects

CNS depression: sedation, drowsiness, dizziness, vomiting, seizures, unconsciousness

Carbon Monoxide (CO)

Most common cause of accidental poisoning death

50-60% CO in air is fatal, dependent on physical condition

Why does alcohol lower amount of CO needed to be fatal?

Alcohol is oxidized by the liver into CO₂, enhancing the effects of CO

Full Steps to Confirmation

1. Urine test is taken first

2. Blood samples are taken to confirm presence

3. Blood is analyzed using GC-MS or LC-MS/MS

Detection window of amphetamines

1-2 days

Detection window of barbiturates

1-3 days (short acting)

1-3 weeks (long acting)

Benzodiazepines Detection Window

1-14 days

Cannabinoids detection window

1-7 days (occasional use)

1-4 weeks (chronic use)

Cocaine detection window

12-48 hours

Opiates detection window

1-3 days

PCP detection window

1-8 days (occasional)

30 days (chronic)