Forensic Toxicology

What is Forensic Toxicology?

Forensic toxicology is the use of toxicology along with a few other disciples like analytical, pharmacology, chemistry and clinical chemistry in medico-legal investigations of death, poisoning and drug use. The main aim of forensic toxicology is the technology and the techniques that are used in obtaining and interpreting the results. This field of toxicology is not too concerned with the legal outcome of the investigation. As per the American Board of Forensic Toxicology (ABFT) the field of forensic toxicology includes the measurement of alcohol, drugs and other toxic substances in the biological specimens along with the interpretation of the results in medico-legal contexts.

There are many areas of specialty within the field of forensic toxicology the main field being the postmortem toxicology. The American Academy of Forensic Sciences (AAFS) emphasizes on the fact that the field of forensic toxicology is very collaborative in nature as a forensic toxicologist is often working in conjunction with law enforcement officers, forensic pathologists, forensic scientists and other crime scene investigators.

The detection of the drugs and other toxic substances present in the biological samples are determined first by an initial screening and then a further confirmation of the right compound and the quantification of the compound. Both the screening and the confirmation are done using different analytical methods.

Forensic Toxicology – Samples

It is necessary that every analytical method in forensic toxicology is carefully tested with a pre-forming validation of the method to ensure the correct and indisputable results each time. A testing laboratory involved in forensic pathology has to adhere to some strict policies to ensure the best possible results and safety of every individual.

The choice of method for investigation and testing mainly depends on what substance is suspected and the type of sample used for testing. In biological samples, many complex factors like the matrix effect, metabolism and conjugation of compounds have to be considerer. Forensic toxicology also aims at finding out the compound statistics of the substances along with their concentrations.

Here is a list and description of some of the samples that are taken from the biological specimens for investigations:

• Urine: The urine samples provide quick and easy results for live subjects. It is most commonly used for drug testing in employees and athletes. The urine samples provide the added advantage that they do not necessarily reflect the toxic substances the the subject is under at the time of collection.
• Blood: A quantity of 10 cubic centimeter of blood is required to screen and confirm the presence of most toxic substances. Unlike the urine samples, the blood sample screen provides the list of toxic substances present in the subject’s body at the time of collection and is hence ideal for testing the blood alcohol content in drunken driving cases.
• Oral Fluid: The layman term for oral fluid is saliva. However, oral fluid is a more appropriate term as saliva is only a component of the oral fluid. The concentration of the toxic substances present in the oral fluid is in parallel to that of the blood. The use of oral fluids is gaining prominence in the fields of clinical settings and drunken driving cases.
• Hair: The hair is an important sample in the field of forensic toxicology as it is capable of providing information about medium to long term history of drug abuse. This is because the chemicals in the bloodstream are transferred to the hair follicle via which a rough timeline regarding the intake of drugs can be deduced. As the hair grows at approximately 1.5 centimeters per month, the cross section of the hair at different intervals will give a rough estimate of when the drug was ingested.

There are many other body fluids and body organs that are collected during an autopsy provide information that will be very vital to a forensic toxicologist. The common autopsy sample is the gastric contents of the subject that is very useful in the detection of undigested pills or liquids that were ingested just before the death. This sample is however not useful in highly decomposed bodies. Some of the other body parts that are used are the vitreous humor of the eye, brain, liver and the spleen.