Same or Different?

Forensic Toxicology vs Forensic Chemistry

Forensic toxicology

Forensic toxicology is the use of toxicology and other disciplines such as analytically chemistry pharmacology and clinical chemistry to aid medical or legal investigation of death, poisoning, and drug use. The primary concern for forensic toxicology is not the legal outcome of the toxicological investigation or the technology utilized, but rather the obtaining and interpreting of the results. A toxicological analysis can be done to various kinds of samples. A forensic toxicologist must consider the context of an investigation, in particular any physical symptoms recorded, and any evidence collected at a crime scene that may narrow the search, such as pill bottles, powders, trace residue, and any available chemicals. Provided with this information and samples with which to work, the forensic toxicologist must determine which toxic substances are present, in what concentrations, and the probable effect of those chemicals on the person.

Forensic chemistry

Forensic chemistry is the application of chemistry to law enforcement or the failure of products or processes. Many different analytically methods may be used to reveal what chemical changes occurred during an incident, and so help reconstruct the sequence of events. "Forensic chemistry is unique among chemical sciences in that its research, practice, and presentation must meet the needs of both the scientific and the legal communities. As such, forensic chemistry research is applied and derivative by nature and design, and it emphasizes meteorology and validation.

Primary Duties

the duties of forensic toxicology

Working in a lab, the forensic toxicologist performs tests on samples collected by forensic pathologists during an autopsy or by crime scene investigators. They use highly sophisticated instruments, chemical reagents and precise methodologies to determine the presence or absence of specific substances in the sample.

the duties of forensic chemistry

A forensic chemist is a professional chemist who analyzes evidence that is brought in from crime scenes and reaches a conclusion based on tests run on that piece of evidence. A forensic chemist's job is to identify and characterize the evidence as part of the larger process of solving a crime. Forensic chemists rarely conduct any investigative work; they handle the evidence collected from the crime scene. Evidence may include hair samples, paint chips, glass fragments, or blood stains. Understanding the evidence requires tools from many disciplines, including chemistry, biology, materials science, and genetics. The prevalence of DNA analysis is making knowledge of genetics increasingly important in this field.

How are they different/

Some forensic chemists may deal with explosives or poisons. The bulk of most forensic chemists work is on the analysis of controlled substances. According to federal and state laws an accurate net weight and positive identification of a substance must be obtained before a person can be tried for its possession, distribution or manufacturing. State and local regulations can vary, but in general an analysis must be accomplished based on certain weight criteria. After the weight is obtained the chemist may perform presumptive testing using chemical reagents that cause a color or odor change. The result of the presumptive tests give the chemist clues that guide what type of further testing is required.

For the definitive identification of a substance there are several analytical instruments a chemist can use.

One instrument is the gas chromatograph-mass spectrometer (GCMS), which is actually two instruments that are attached. The gas chromatograph is essentially a very hot oven holding a hollow coiled column. A drug sample is diluted in a solvent (e.g.: chloroform, methanol) and is injected into this column, the solvent will evaporate very quickly leaving the drug to travel through the column. The amount of time it takes the drug to travel through the column to a detector is recorded and compared to a known drug. (e.g. cocaine, methamphetamine, heroin, etc.) Gas chromatography alone is only a tentative identification. Once the drug has passed the detector it is sent into the mass spectrometer. A mass spectrometer identifies prominent ions of a drug. It accomplishes this by bombarding the drug with electrons, thus breaking it into its specific ions. This process is also recorded and the results are compared to the known drug.

Another instrument used to identify controlled substances is Fourier Transform infrared spectrophotometer (FTIR). The FTIR records the bending and stretching of molecular bonds that are exposed to infrared light. The molecular bonds of all compounds react differently and create unique patterns upon exposure to a beam of infrared light. The unique pattern created is known as the fingerprint for that drug. As with the GCMS the results of the FTIR are compared to a known drug sample, thus producing a definitive identification.





Forensic toxicology is the use of toxicology to aid medicolegal investigation of death, poisoning, and drug use. Many toxic substances do not produce characteristic lesions, so if a toxic reaction is suspected, visual investigation may not suffice.

A forensic toxicologist must consider the context of an investigation, in particular any physical symptoms recorded, and any evidence collected at a crime scene that may narrow the search, such as pill bottles, powders, trace residue, and any available chemicals. Provided with this information and samples with which to work, the forensic toxicologist must determine which toxic substances are present, in what concentrations, and the probable effect of those chemicals on the person.

Determining the substance ingested is often complicated by the body's natural processes, as it is rare for a chemical to remain in its original form once in the body. For example: heroin is almost immediately metabolised into morphine, making detailed investigation into factors such as injection marks and chemical purity necessary to confirm diagnosis. The substance may also have been diluted by its dispersal through the body; while a pill or other regulated dose of a drug may have grams or milligrams of the active constituent, an individual sample under investigation may only contain micrograms or nanograms.
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