Why thieves wear gloves? Chemistry of the Fingerprints


Most criminals wear gloves during their illegal activities. What are the reasons behind this? Sometimes one may think they do not want to touch their victims with their bare hands. They are wearing gloves since they do not want their fingerprints to remain on the crime scenes. In this post, you will learn about fingerprints, types, locations of fingerprints, and the formation, of fingerprints and fingerprint processing and how the thieves can be identified by fingerprints at the crime scene.



Fingerprint
The fingerprint is the imprint left by the human finger friction ridges on object surfaces.  Fingerprints are essential in forensic science for the identification of a person at a crime scene. They are readily deposited on appropriate surfaces such as porous (paper, wood, and cloth) and non-porous (metals, plastic, polished stone surface and plastic) surfaces.  Fingerprints occur when secreted sweat from the eccrine glands existing on the finger epidermal ridges or blood, dirt etcetera from thumbs or fingers are deposited on the object surfaces.  

 Types and locations of fingerprints
Fingerprints are grouped into three categories based on the surfaces they are found and whether they are invisible or visible. According to this classification, fingerprints that occur on soft surfaces like soaps, wax, and wet paint etcetera are known as three-dimensional plastic prints. The prints that are found on hard surfaces can either be latent or patent prints. The latent prints are prints that are not visible while the patent prints are visible.  

Also read: Young Kenyan Innovators

Formation of fingerprints
Patent prints are formed when the substances such as blood, ink, dirt and so on are transferred from the thumbs or fingers to the surface. This type of fingerprints is found on the porous surfaces. Latent prints are formed when the sweat and body’s natural oils are deposited on the other surfaces. Latent prints exist on various surfaces especially on non-porous surfaces, but, they are not easily visible thus their detection needs the use of chemical reagents, fingerprint powder and to some extent the employment of the alternate light sources.

Processing of fingerprints
The widely processed fingerprints at the crime scene are the patent and latent prints. The patent prints are collected by taking their photographs. For the high quality of the processed patent prints, the photographs are taken by the high-resolution forensic cameras. Latent prints are discovered and collected by dusting the surfaces (smooth or non-porous) by the fingerprint powder. If the latent prints exist on the surface, they are photographed and lifted from the surface using an adhesive tape.  For the preservation of the print, the lifting adhesive tape is placed in the latent lift card. Fingerprint powder can interfere with the evidence at the crime scene, therefore, barring further use of other techniques which can reveal the hidden prints. In this case, the application of the alternate light source or cyanoacrylate is necessary.  

Also read: The Ostwald Process

Identification of thieves
The forensic scientists use all types of fingerprints to identify the persons responsible for the crime. According to genetics, every person has a unique fingerprint, and this makes it possible to determine people according to their fingerprints. The criminals are aware of this and that why they wear gloves. However, the gloves can also be used to identify them, if they drop the gloves at the crime scene.  

For more about the examination and analysis of the prints find them here(Forensic Resources).

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