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The Field of Forensic Toxicology

Aaron Jura, Millicent Kelly
  • Author
    Aaron Jura

    Mr. Aaron Jura holds a Juris Doctor degree, a masters degree in American History, and a bachelors degree in Liberal Arts. Mr. Jura has worked as a K-12 educator for 8 years and teaches English Language Arts, Social Studies, and Special Education in Louisiana. Mr. Jura serves as a Teacher Leader Advisor for the state department of Education and sits on numerous committees and boards supporting public education.

  • Instructor
    Millicent Kelly

    Millicent has been teaching at the university level since 2004. She holds a Bachelor's degree in Criminal Justice and a Master's degree in Human Resources.

Understand what forensic toxicology is by learning the forensic toxicology definition. Explore the process and three main concerns of forensic toxicology. Updated: 04/02/2022

Table of Contents


What Is Forensic Toxicology?

Forensic toxicology is the field of forensics that determines when the ingestion of harmful agents or illicit drugs might lead to potential legal or criminal consequences. Forensic toxicology is a subcategory in the field of toxicology, which is the study of the harm that harmful substances might have on the human body. Many consequences might befall a person if they ingest a harmful agent. Illicit narcotics can cause intense physical harm and even death. Subsequently, the addiction may occur based on the use of these same illicit drugs is dangerous. Some chemical compounds are also harmful when ingested. Forensic toxicologists must determine the substances present and how they may have impacted the victim.

Forensic toxicology does not only involve the testing for substances in the human body after a crime is committed. There are also valid reasons to use forensic toxicology outside of the criminal justice system. One example is in the pre-employment screening of applicants for a job with a particular company. If the company requires substance testing for applicants, that is an example of pre-employment forensic toxicology. Some employers utilize drug testing for pre-employment or randomized samples collected to ensure they maintain a drug-free workplace.

Instances Where Forensic Toxicology Is Used

Most commonly, forensic toxicology is used in the following settings:

  • Criminal investigations
  • Pre-employment and continuing employment screenings
  • Investigations into substance abuse in sports, including allegations of doping
  • Medical settings

Forensic toxicologists are concerned with the impact illicit drugs or harmful chemicals might have on the human body. The work of a forensic toxicologist primarily focuses on the following three concerns:

  • Whether a substance could cause death or harm the body.
  • Whether a substance could alter behavior or impair judgment.
  • Whether a substance could have a legitimate reason for being present in the human body.

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Process of Forensic Toxicology

Forensic toxicology follows a fairly prescribed step-by-step process that begins when a sample is collected. Samples might be collected from a living subject in a lab setting, collected from a deceased subject, or collected elsewhere and provided to the toxicologist for testing purposes. Oftentimes, in investigations, pre-employment, or medical settings, there will be a chain of custody notation made on the sample itself or the envelope that highlights who had access to the sample being tested from the point of collection.

The type of sample might vary depending upon the type of toxicological testing being conducted. For example, blood testing can be used to detect the presence of alcohol within the bloodstream, as long as the body has not yet metabolized it. Forensic toxicologists can use the vitreous humor, the viscous liquid-type substance in the eye, to determine if alcohol was present in the body at the time of death, while the body may have already metabolized the alcohol content in the bloodstream. They will often use urine, blood, hair samples, or other biological materials to assess levels of toxicity in the body.

Other biological materials might include fingernail or toenail clippings, the contents from a deceased victim's stomach, pieces of bone or bone marrow, or spinal fluid which may be extracted through a lumbar puncture, otherwise known as a spinal tap.


Urine samples are the most common type of material tested in forensic toxicology. These samples are collected from both people who are alive and deceased. A benefit of testing urine samples is the amount of time it takes to be assessed, which takes much less time than assessing blood or hair samples. Many hospitals have the means to test a urine sample almost immediately after it is collected, which may aid in a patient's timely treatment.

Some drugs have a longer life in urine than others. For example, the presence of tetrahydrocannabinol (THC) in marijuana might last up to 30 days in the subject's urine whereas heroin might only last one to three days in the urine. Urine collection and assessment are commonplace in pre-employment and ongoing employment screenings mainly because it is easy to collect and affordable to test.


Blood samples are another common sample type in forensic toxicology. Often during an investigation, blood and urine samples will be collected simultaneously. Blood samples can be frozen, which aids in the preservation of the materials for testing. Blood-based testing is affordable enough to use as a preliminary assessment in forensic investigations. By assessing the blood of a deceased person, the medical examiner or coroner is better able to limit the types of tests required and thus has more fiscal control over the budgetary needs of an investigation.

A minimum of 20 millimeters of blood should be collected for most forensic toxicological needs. Foreign substances, even in trace amounts, can be detected in blood samples. However, this amount varies depending upon the type and number of tests required on a particular patient or case.

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Frequently Asked Questions

What is an example of forensic toxicology?

An example of forensic toxicology is pre-employment and ongoing employment substance screenings. Oftentimes, an employer will require applicants and employees to submit to drug testing that is conducted by a forensic toxicologist. Most frequently the sample will include urine, but some employers take the assessment a step further and require hair samples since some drugs can be metabolized quickly in urine samples.

What are the 3 primary concerns of forensic toxicology?

Forensic toxicologists are most interested in the following three primary concerns. These concerns include: whether a substance could cause death or have a harmful impact on the body, if a substance could alter behavior or impair judgment, and/or whether a substance could have a legitimate reason for being present in the human body.

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