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Forensic Toxicology

Updated on October 11, 2013

What is Forensic Toxicology?

Forensic science is defined as 'the application of the techniques of science to legal matters, both criminal and civil. Forensic science includes a number of disciplines and sub-disciplines'. Forensic scientists, or forensic laboratory technicians, are responsible for the scientific analysis of items of evidence recovered during a criminal investigation. They are also required to preserve evidence, maintain continuity of evidence (also referred to as chain of evidence), report their findings in written form and occasionally they are required to give testimony of their findings in criminal investigations which are appearing in court.

A forensic toxicologist refers to a forensic laboratory technician specialising in the toxicology field. Forensic toxicology is defined as 'the analysis of drugs and poisons in blood and bodily fluids'. A poison is defined as 'any substance that, when relatively small amounts are ingested, inhaled, or absorbed or applied to, injected into or developed within the body, has a chemical action that causes damage to the structure or disturbance of function, producing symptoms, illness or dead'. Though the role of a forensic toxicologist is primarily based in a laboratory, in certain criminal investigations they are also required to attend court in order to testify to their findings or provide expert testimony in cases.


Forensic toxicologists are required to have a strong background in chemistry. There are a number of courses throughout Australia which offer undergraduate forensic science degrees, though these courses are not available in all states and territories. As far as courses which specifically train students in forensic toxicology, Murdoch University in Western Australia is one of the only universities to offer the course with their Bachelor of Forensic Biology and Toxicology.

Most forensic science courses in Australia offer the option of either forensic biology or forensic chemistry as a major, in which toxicology is studied and the necessary skills to work in the industry are gained. The educational requirements for a career in forensic toxicology can also be covered with general chemistry based courses, such as the University of Canberra's Bachelor of Pharmaceutical Science, and several other universities which offer bachelor degrees in analytical and forensic science as a combined chemistry degree.

Upon graduation, accreditation can be gained through the National Association of Testing Authorities, Australia (NATA). This accreditation is based on a peer review process. As part of NATA, the Forensic Science Accreditation Advisory Committee consists of seven members who, between them, cover most major areas of forensic science, including toxicology, and are considered experts in their various fields. There are also a variety of memberships to institutes and societies available to those who have studied forensic toxicology, such as the Australia and New Zealand Forensic Science Society (ANZFSS), the Australian Academy of Forensic Sciences, the Royal Australia Chemical Institute (RACI), The International Association of Forensic Toxicologists (TIAFT), and the Australasian Society of Clinical and Experimental Pharmacologists and Toxicologists (ASCEPT) as well as others.


Working as a team

Forensic toxicologists will work with other forensic scientists, medical personnel and crime scene officers. The crime scene co-ordinator is responsible for managing the necessary scientific support required for an investigation or case, though evidence collected at any crime scene is sent to the forensic toxicologist through the force's submissions system by the Scene of Crime Officer (SOCO).

A forensic toxicologist may work with a forensic pathologist or police surgeon in the recovery of fluids for analysis and may also associate with other individuals in the forensic field, such as road transport investigators and drug analysts. Forensic drug analysts differ from forensic toxicologists in that the forensic drug analyst will work with physical evidence such as powders, plant material, paraphernalia and equipment seized from clandestine laboratories. While a forensic toxicologist will work with 'biological samples and must consider absorption of the material, distribution in body tissues, metabolic conversions, movement through the system, persistence of the drug and modes of excretion'.

The role the forensic toxicologist plays to the forensic pathologist (or coroner), is essential. Forensic medical practitioners rely on the forensic toxicologist to 'assess exposure to drugs and foreign substances in cases of suspected assaults including rapes and homicides, to assist in the determination of death and in determining the possible influence of foreign substances in misadventures including workplace deaths and motor vehicle crashes'.

Learn more about Forensic Toxicology!


Though the duties of a toxicologist can be quite varied and can include tasks such as studying the amount of exposure from a pollution source (for example industrial waste products) and the potential effect it may have on living organisms, the ecosystem and public health, the roles and duties of a forensic toxicologist are quite specific.

Forensic toxicology can be broadly categorised into three distinct areas; post-mortem toxicology, human performance toxicology and drug testing. In these areas, the forensic toxicologist will determine the absence or presence of volatiles and other drugs and chemicals in a variety of biological samples.

Post-mortem toxicology refers to the analysis of bodily fluids for drugs or poisons after death. This can include the analysis of fluids, such as blood, and the identification and analysis of poisons and drugs in a deceased person, along with residue found at the crime scene. In this area of forensic toxicology, the forensic toxicologist 'aids in establishing the cause and manner of intoxication or death through the analysis of various fluids and tissues obtained during autopsy'.

Human performance toxicology refers to the evaluation of 'the role of drugs in the modification of human behaviour, usually applied to traffic safety and the operation of a motor vehicle'. Blood alcohol concentration (BAC) in an individual, for example, falls under this category of forensic toxicology and is one of the most common roles in forensic toxicology.

Drug testing is defined as 'demonstrating prior use or abuse of selected drugs through the analysis of urine'. Forensic toxicologists working in this field will generally test the urine of individuals such as athletes or employees for traces of illicit or performance enhancing drugs.

Forensic toxicologists will, generally speaking, primarily work with biological samples. A biological sample refers to a sample of a part of an organism. For example, organs, tissue, blood, urine, bile and other fluids are considered biological samples and frequently tested by forensic toxicologists. Lung tissue for example, can be tested to establish the presence of any poisons which have been administered by inhalation. Blood and urine can both be tested for the presence of drugs (including alcohol). One of the most common samples a forensic toxicologist will encounter is blood taken for alcohol content analysis.

Through presumptive tests, qualitative and quantitative analysis, a forensic toxicologist is able to not only determine the presence of drugs in biological samples, but also the quantity of the substance present in the sample. Presumptive testing and qualitative analysis refers to the analysis of a sample to determine the presence of drugs or poison in it. Two common presumptive tests are thin layer chromatography (TLC) and immunoassay techniques.

Quantitative analysis refers to the analysis of a sample to determine the amount and concentration of drugs or poison found. Other techniques used for testing, once presumptive tests have been confirmed, include infrared spectroscopy (IR), gas chromatography/mass spectrometry (GC/MS) and high pressure liquid chromatography/mass spectrometry (HPLC-MS).

Mass Spectrum
Mass Spectrum | Source

Forensic Toxicology in Forensic Investigations

An example of these techniques coming together in a forensic investigation is if a post mortem blood sample was obtained from a victim who died in a car accident, the forensic toxicologist would analyse the blood sample using qualitative analysis to determine whether there was any traces of drugs, medication or alcohol present in the blood. If the findings are positive, the forensic toxicologist would then use quantitative analysis to determine the amount and concentration of the drugs, medication or alcohol present. Continuing this example, if ethanol (alcohol) was found initially in the qualitative analysis, Blood Alcohol Concentration (BAC) can then be established by the forensic toxicologist using quantitative analysis. With this information, the forensic toxicologist can then determine whether or not the alcohol was a contributing factor in death. If the BAC is over the legal limit (0.05 grams of ethanol per 100mL of blood in Australia) then it may be determined that alcohol did play a factor in the car accident, and death of the victim.

Given that the forensic toxicologist has training in pharmacology, defined as the study of preparation, properties, uses and actions of drugs, they are able to determine whether the concentrations of any substances found in the samples they are working with, fall into the category of therapeutic dosage (in the case of medicinal drugs such as those prescribed to an individual by a doctor or available over the counter), intoxication or overdose or death. If, for example, a forensic toxicologist has a post mortem blood sample of an individual which contains a medication like alprazolam (xanax), a benzodiazepine class drug used primarily to treat anxiety, they will determine the concentration of the drug found in the sample. If the prescription information has been recovered (through bottles found at a crime scene for instance, or through medical files) then the forensic toxicologist is able to determine the dosage the individual was meant to be taking and compare this with the actual concentration found. If the amounts differ greatly, it may be necessary to consult with the forensic pathologist in order to determine, through analysis of organs, whether or not there was a history of drug abuse present in the individual which may account for the difference as often when a tolerance to a drug is gained by an individual, they require more of the drug than would be found in others without that tolerance. After obtaining all this information, the forensic toxicologist can analyse their findings and state their opinion on whether the dose was therapeutic, or lead to an overdose causing death. Drug interactions will also be examined, as it may be found that while a medication has been ingested, it was the interaction with another medication, drug or alcohol which was a factor in the individual's death. Ultimately though, the cause of death can only be established and signed off on, by the forensic pathologist, or toxicologist.

In certain cases, forensic toxicologists are also able to ascertain whether or not a crime has actually been committed or not. For example, if a person is found in possession of a substance that is suspected to be cocaine, or another illicit drug, the forensic toxicologist is then able to analyse the substance, and by comparison to a control substance (such as cocaine), they are then able to determine whether or not the sample collected is an illicit drug and charges can be made appropriately, if necessary.

Another role forensic toxicologist's play is in determining whether a non-biological sample contains drugs or poisons. For example, if alcohol has been ingested but there are traces of other drugs in the blood sample and the alcohol bottle is available, forensic toxicologists may test to see whether or not the bottle contains traces of the drugs present in the blood sample.


Other Responsibilities

All forensic laboratories, and personnel working in them (including forensic toxicologists), must also adhere to the international standards laboratory requirements. These including possessing the necessary skills and knowledge to carry out tasks, full documentation and proper control of reference collections, maintaining chain of custody, engaging in quality control, presentation of results which comply with appropriate standards and other roles. Forensic toxicologists must also adhere to the standards of uniform drug testing, in medical, sport and workplace drug testing.

Continuity of evidence must be maintained by forensic toxicologists, along with every other member of a criminal investigation who has access to the evidence recovered; for example scene of crime officers (SOCOs), police scientific support unit (SSU), forensic pathologist or coroner, and forensic laboratory technicians. Continuity of evidence refers to the complete documented record of each item of evidence recovered from a crime scene. Continuity of evidence is important, as any evidence which has not been properly documented may be deemed inadmissible in court, which in turn may adversely affect the outcome of a criminal investigation.

Preservation of evidence is also another role which applies to forensic toxicologists, along with the other members of a criminal investigation. Preservation of evidence refers to the protecting the integrity of evidence, along with the prevention of contamination of evidence. There are established steps taken to prevent contamination from occurring, such as using chain of custody labels, the opening of packaging containing evidence in an area other than where the package was originally sealed, minimising the amount of people handling the evidence and correct, secure storage of the evidence.

The reporting of findings is another major role of members of a criminal investigation, including the forensic toxicologists. The findings report is usually used in court, rather than the testimony of the forensic toxicologist (though this is not always the case. The report must cover all aspects of the forensic toxicologist's findings, and must be comprehensive. The report must also be written so it is easily understood by people outside the science community, such as lawyers and individuals on a jury if one is present in the court case.

Occasionally, though not often, the forensic toxicologist is required to present their findings in court. They can also appear to testify their opinion on their area of expertise (toxicology).

The role of a forensic toxicologist is varied and the forensic toxicologist plays an important role in many different types of criminal investigations. Forensic toxicologists require a strong background in chemistry and pharmacology and a range of skills and attributes to enable them to do their job. Forensic toxicologists work with a range of other forensic experts, from those who deal with the collection of evidence, to medical professionals, to road transport investigators and many others involved in the forensic science industry or field. The analysis of drugs in a biological samples, though the main description of what a forensic toxicologist does, is only one of the roles and duties of the forensic toxicologist, and only one part of their overall role as part of the forensic investigation team.

Learn more about Forensic Toxicology as a career


Bell, S. (2004). Encyclopedia of Forensic Science. New York: Facts On File, Inc.

Drummer, O (2007). Best practice Forensic Toxicology, Forensic Science International, 169 (1), S29.

Goldberger, B. A, Polettini, A. (2002). Forensic toxicology: web resources, Toxicology, 173(1,2), 97-102.

Jackson, A. R. W, Jackson, J. M. (2008). Forensic Science, 2ed, Essex: Pearsons Education Limited.

Martin, D. M. (2010). An overview of Present and Future Drug Testing, The Journal of Global Drug Policy and Practice, 3(4).

Stout, P. R. (2009). Forensic Toxicology: Information Resources in Toxicology (4ed). Retrieved from EBook Library.

W.B Saunders Company. (2000). Dorland's Illustrated Medical Dictionary, 29ed. Philadelphia: W.B Saunders Company.

Want to learn more about Forensic Science?


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    • profile image


      4 years ago

      Does a forensic lab require a certain quality of a controlled substance (methamphetamine) in its analysis verifying the product as well as ruling out false positives?

      What forensic type of testing for methamphetamine rules out false positive? Is it possible?

      How much methamphetamine does it take to stimulate the central nervous system.

    • rebeccamillar profile imageAUTHOR

      Rebecca Millar 

      5 years ago from Melbourne, Australia

      Interesting question, but unfortunately not one I know the direct answer to. I do know that there have been at least 36 studies published on that topic, including one by Harvard, and I have strong opinions on the lack of funding for some areas but funding for projects I disagree with morally - but they're just that; opinions, not facts. It's frustrating when the progress of science or things like this are halted because it doesn't suit somebody high up.

    • someonewhoknows profile image


      5 years ago from south and west of canada,north of ohio

      What happens when someone in power decides that what you find isn't in their best interests .Especially those who fund research in order to control the outcome of that research? I've heard of this happening before where an expert in toxicology found that fluoride in water supplies was lowering the I Q of children.Needless to say she was never funded for any further research on the subject.

    • rebeccamillar profile imageAUTHOR

      Rebecca Millar 

      5 years ago from Melbourne, Australia

      A medical background is always a huge advantage for anything science related - in Australia a lot of our university science students actually take the same chemistry subjects as medical students do. There are quite a few post-graduate toxicology courses available too, including the option of a masters.

    • Majidsiko profile image


      5 years ago from Kenya

      Very informative. Reminds me of CSI and stuff. Thanks for the education. Will it be an advantage if i have a medical background. Can it be done as a masters/fellowship after a primary medical degree.


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