The Role of Chemistry in Processing Crime Scenes

Every chemist is schooled in general, organic, and analytical chemistry, but forensic chemists also specialize in specific areas of expertise. For example, an inorganic chemist may examine traces of dust by using microchemistry to identify the chemical composition of tiny particles. Another chemist might employ thin-layer chromatography during the analysis of Forensic scientists examine evidence from crime scenes in an effort to solve crimes. This scientist is removing a piece of blood-stained material gathered at a crime scene for DNA testing.
 

The physical contact between a suspect and a victim, vehicle or a crime scene during the commission of a crime, can and often does result in the transfer of materials such as blood, semen, saliva, hairs, fibers, paint, plastic and adhesives. Also, in the investigation of fires, the analysis of fire debris samples for the identification of ignitable liquids is necessary to help determine the cause and origin of the fire.
 

The Forensic Chemistry Section of the Crime Laboratory is responsible for the examination, identification and/or comparison of these types of materials which may be present at the crime scene, on the victim, the suspect, clothing articles, vehicles, weapons, tools and other objects. In order to conduct these examinations, various serological, chemical, microscopic, and/or instrumental techniques are utilized.[11]
 

The truth is that a forensic scientist is often a chemist. This because the analysis of gunshot residues, hair or traces of blood that can link a suspect to a crime scene, is above all a process that uses the techniques of chemistry, instruments developed for chemistry and (note!), the methods for solving problems of chemists! I

 

n fact, modern criminal investigation puts the limits and capabilities of the so called Analytical Chemistry to the test: a branch of chemistry that focuses on identifying the quantities of substances present in a sample. What about blood tests? Analytical chemistry, of course! The development of analytical chemistry made it possible to detect the presence of substances in minuscule quantities, through a variety of techniques capable of recognizing the specific characteristics of each substance. For example, with chromatography (a technique that allows to separate the various components of a sample), it is possible to detect absolutely minute quantities of sample in the order of nanograms per milliliter. And how much is that? Less than a packet of sugar dissolved in an Olympic swimming pool! In the case of metals, can go up to 10 times further. Using a technique of vaporization of the sample at 10 000 degrees Celsius, it’s possible, for example, to detect the presence of a toxic metal in a hair in a proportion equal to one gram of metal into four Olympic pools!
 

But the great challenge of analytical chemistry applied to criminal investigation goes beyond identifying the presence of drugs, explosives or poisons. It’s about how to characterize the materials found at the crime scene and trace them back to their origin.In fact, the composition of materials such as glass fragments, traces of paint, textile fibers, paper or even the ink used to write a letter, can provide very important clues in the investigation of a crime. The combined use of analytical techniques allows identifying even the geographical origin or date of manufacture of many materials.[14].

Some important techniques of forensic chemistry are following;

• Trace Evidence

• Fingerprinting

• Testing for Alcohol

• Serology

• Bloodstain Pattern Analysis

• Fire Debris Analysis

• Toxicology

Reference:
Manika Barar, Department of Chemistry, SIMT College Meerut, India International Journal of MediPharm Research, Vol.02, No.01, pp 10-16, 2015
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