forensic toxicology

Mathieu Orfila

• chairman of the legal medicine department at La Sorbonne in france, published a book in 1814

• first attempt to systematically study and classify poisons

• orfila was the first to articulate the fact that poisons must be absorbed, or enter the blood, to manifest their effects

first forensic toxicologist in the USA

alexander gettler, Ph.D. 1918-1959

what is toxicology

the study of adverse effect of chemicals

toxicology is a quantitative science, dosage matters

what is forensic toxicology

the application of toxicology to the chemical analysis of material, ususally the human body fluids and/or tissues, the results of which are intended to be introduced as evidence in legal documents 9death certificate) or proceedings (criminal cases or administrative hearing)

types of forensic toxicology

• post mortem

• human performance DUI

• urine drug testing/workplace testing

• clinical medical-legal investigations

the objective of a forensic toxicologist

• to determine what types and how much of a poisonous substance is present

• interpret the results to understand the episode of intoxication

how do you study a chemical?

• determine its chemical and physical properties

• determine its effect on living organisms

• identify and determine the amount of it in the biological specimens

• develop antidotes

determine the chemical and physical properties of substances

chemical and physical properties of a substance effects the pharmacokinetics of the substance

absorption, distribution, metabolism, elimintation

absorption

a drug must cross membranes in order to become active

four major routes of administration:

oral, injection, inhalation, topical

distribution

a drug will relocate in the body to a site where it will be active

location is based on:

hydrophilicity - water loving

lipophilicty - fat loving

size of drug molecule

blood perfusion

metabolism

the body recognizes a foreign substance as a toxin and works to protect itself

liver is the primary organ which detoxifies foreign substances

detoxification includes: inactivating the substance

making it more water soluble so it is easier to eliminate

elimination

any tissue which makes anything with access to the external environment represents a potential route for elimination: urine, tears, milk, sweat,feces, hair, saliva, expired air , nails

determine physiological effects of substances on living organisms

pharmacodynamics

drug_> effect

identify and determine the amount of substance in biological or non-biological materials

1. screen all samples

   • immunoassay

   • TOF MS, orbitrap MS

2. confirm initial screenings results

   • extract drug from tissue sample by adjusting the PH

   • two popular instruments used to separate and identify drugs and quantitate

   • GC/MS

   • UHPLC which is high performance liquid chromatography

3. quantify the drug

forensic toxicology more

less recognized and more meaningful role as a guardian of public health

• recognized the rising heroin epidemic in the 60s and 70s and brought national and local effort to control usage

• monitor blood levels of lead in children

• assess potency of drugs and efficacy of antagonists

• test blood from persons arrested for impaired driving

• test urine from parolees

• federaly regulated urine drug testing

questions answered by post-mortem toxicology

• fatal, is it enough?

• drug influence circumstances of death?

• is the case history true?