Forensic Toxicology

Role of Forensic Toxicologist Toxicologist detect and identify drugs and poisons in body fluids, tissues and organs. Toxicologists found that ethyl alcohol is the number 1 abused drug in Western countries. 40% of all traffic deaths in the US are alcohol related (that makes 17,500 fatalities per year and 2 million injuries)

Toxicology of Alcohol-1 Metabolism Absorption and Distribution Alcohol is a colorless liquid and appears in the blood w/in minutes of consumption. Absorption Phase: Absorbed from the stomach into the small intestine then into the blood stream During the absorption phase alcohol is carried to all parts of the body-distributed uniformly in the watery parts of the body. Rate of absorption depends on: time taken to consume, alcohol content of beverage, amount consumed, quantity and type of food present in gut. When this phase is over a max level of alcohol is in the blood and post absorption begins and the alcohol level decreases.

Toxicology of Alcohol-2 Metabolism cont. Elimination By two methods: Oxidation Nearly all the alcohol consumed is oxidized into CO2 and water Occurs in the liver using an enzyme called alcohol dehydrogenase Excretion Remaining alcohol is excreted unchanged in the breath, urine, and perspiration. Burn off rate varies (.015% weigh per volume per hour) can vary as much as 30% b/w individuals

Toxicology of Alcohol-3 Metabolism cont. Blood Alcohol Concentration Blood is used to determine quantity consumed and is directly proportionate to the concentration in the brain. Alcohol is concentrated evenly through watery portions of the body, which aids examiners when blood is not available.

Toxicology of Alcohol-4 Alcohol in the Circulatory System Ingestion and Distribution Via Mouth  Esophagus  Stomach  Portal Vein  Circulatory system  Liver  Heart: right atrium then the right ventricle  Lungs via pulmonary artery Aeration Lungs: As CO2 and O2 are exchanged in the lungs any volatile substance present will also enter the alveoli where the gases are exchanged. CO2 and alcohol are released Henry’s Law explains how alcohol will divide itself b/w blood and the air. Pp

Toxicology of Alcohol-5 Alcohol in the Circulatory System cont. Recirculation and Absorption Pulmonary Vein  Left atrium  Left Ventrical  Arteries  Capillaries  Body Tissues  Veins  Back to the heart. Fig 6.2 pp206 Concentration of alcohol is considerably higher in arterial blood than in venous blood during the absorption stage After absorption stage alcohol is equally distributed through the blood system.

Testing for Intoxication-1 Breath Testing for Alcohol Breath Test Instruments Breathalyzer: developed by R.F. Borkenstein in 1954 See Closer Analysis pp IR Light absorption devices See Closer Analysis pp Fuel Cell Detectors: a detector in which a chemical reaction involving alcohol produces electricity. Both tests above produce self-diagnostic tests as well as undergo a sequence of steps that produces a readout of a subject’s test results See closer Analysis pp 214

Testing for Intoxication-2 Breath Testing for Alcohol Considerations Avoid measuring mouth alcohol Subject must be monitored to not have belched, regurgitated or put any foreign material into their mouth 20 min. before the test. Measurement of duplicate breath samples Done minutes apart Checks the integrity of the test Reduces possibility of errors from the operator, mouth alcohol, instrument failures, and spurious electric signals

Testing for Intoxication-3 Field Sobriety Testing Used by law enforcement to estimate a motorist’s degree of physical impairment by alcohol and to determine whether an evidential test for alcohol is justified. Psychophysical tests: Horizontal-gaze nystagmus test (involuntary jerking of the eye) Horizontal-gaze nystagmus test (involuntary jerking of the eye) walk and turn one-leg stand

Analysis of Blood for Alcohol-1 Collection and Preservation Procedures used for analysis: Gas Chromatography most widely used. Oxidation used in clinical or hospital setting. Collection Blood drawn in medically accepted conditions Preservation Sealed in an airtight container after adding and anticoagulant (potassium or EDTA) and preservative (sodium fluoride). Store at appropriate temperature Postmortem collection requires samples from several body parts preserved and refrigerated.

Alcohol and the Law-1 Blood Alcohol Laws/Constitutional Issues Current legal measure of drunk driving the US is a blood alcohol concentration of 0.08%, or 0.08 grams of alcohol per 100 millileters of blood 5 th Amendment guarantees protection against self- incrimination An implied-consent law states that the operator of a motor vehicle on a public highway must either consent to a test or lose his license.

Role of the Toxicologist-1 Challenges Must devise an analytical scheme to detect, isolate, and identify toxic substances extracted from biological fluids, tissues, and organs. Toxins can be metabolized to nanogram and microgram amounts Substances injected might not always be extracted. Ex: Injected heroin is immediately metabolized into morphine

Role of the Toxicologist-2 Collection and Preservation Collection Deceased persons: decide which specimens should be shipped Living persons: collect urine and blood samples 2 urine samples are taken consecutively

Role of the Toxicologist-3 Techniques Used Acids and Bases By controlling the pH of a water soln. in which blood, urine, or tissues are resolved toxicologists can extract and categorize drugs. Acid drugs are removed from acidified water soln. Basic drugs are removed from basic water soln. Acid Drugs Basic Drugs Barbiturates Phencyclidine Acetylsalicylic Acid Methadone Amphetamines Cocaine

Role of the Toxicologist-4 Techniques Used Screening Tests TLC, GC, and immunoassay most widely used Immunoassay based on antibody reactions and detects small concentrations of drugs in body fluids and organs Confirmation Tests GC/Mass Spectrometry combo is used to confirm a positive screening test. See Fig 6-11 pp225

Role of the Toxicologist-5 Techniques Used Detecting Drugs in Hair Case Study: pp228 Hair is an alternative to blood and urine. As hair grows, drugs location on the hair shaft presents a timeline. Can date weeks, months, and years depending on hair length Detecting Nondrug Poisons Heavy Metals: Reinsch Test: suspect tissues are dissolved in HCl and a copper strip is inserted. Carbon Monoxide: Spectrophotometric Methods: measure visible spectrum in blood GC

Role of the Toxicologist-6 Significance of Findings Once a drug is extracted and identified, a toxicologist may be required to judge the drugs effect on an individual’s natural performance or physical state.