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What is forensic chemistry?

Forensic chemistry is the branch of chemistry that helps resolve criminal acts through the study of organic and inorganic compounds present at crime scenes, such as gunpowder, tissues, body fluids, pigments, toxins, materials, etc.

The application of forensic chemistry requires thoroughness and attention to detail, and it includes qualitative and quantitative methods. The work is carried out both at the scene and in the laboratory, and it consists of three major phases:

  1. Collecting and cataloging samples and evidence.
  2. Analyzing the samples.
  3. Interpreting the results.
  4. Descriptive report.

When did forensic chemistry originate?

Forensic chemistry started in the 19th century, when the increasing advancement of science began to allow its application in other fields. The first famous case of using chemistry to solve a crime was the case of Mary Ann Cotton, the first recorded female serial killer in history.

Some of Mary Ann’s comments and the immediate death of her son, Charles Edward Cotton, raised the suspicions of Thomas Riley, her parishioner, who opened an investigation. Even though death had apparently been due to natural causes, when some samples collected by Charles Edward’s doctor were analyzed, it turned out that they contained arsenic.

The event piqued the interest of the local press, which discovered more about the course of Mary Ann’s life: over 20 years, she had moved several times, leaving behind a trail of husbands and children, all dead of what was supposed to be typhus (typhoid fever) or other gastrointestinal complications. The deaths did not attract attention because typhus epidemics were still common at the time, but all of them had preceded the collection of life insurance.

In all, Mary Ann Cotton is alleged to have murdered about 21 people, including three husbands, two lovers, a friend, her mother, and 12 of her 13 children. This first known case when chemistry made it possible to solve a crime is representative of the importance combining scientific and analytical procedures has for forensic chemistry.

What are some of the most common procedures in forensic chemistry?

  • Spectroscopy: thanks to the Fourier-transform infrared spectroscopy (FTIR) technique, it is possible to separate, identify, and quantify the components of an unknown substance. The mass spectrometer and the gas chromatograph are used for this.
  • Chromatography: used to analyze liquid residue. It is mainly used to identify possible accelerants that demonstrate the intentionality of a fire or to identify inks on paper samples.
  • Microscopy: used to better observe fabrics or fibers (such as hair, fabric, etc.) and identify elements that are not observable with the naked eye. Thanks to magnification, it is possible to see any residues of soil, food, body fluids, etc.
  • Use of luminol: luminol is a derivative of phthalic acid that makes it possible to detect traces of blood. The chemical reaction produces a blue luminescence.

What sciences contribute to the application of forensic chemistry?

Other sciences are also applied in the forensic field, complementing the analyses and results that can be obtained with forensic chemistry. Some of these include:

  • Ballistics.
  • Biology.
  • Entomology.
  • Anthropology.

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