The Chemistry of Criminal Investigation

The Chemistry of Criminal Investigation

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For lovers of crime shows on TV the importance of chemistry in the criminal investigation is not a surprise. But today we will talk about the science behind the fiction!

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!

In 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.

We’ll give you an example: if you’ve ever read the label on a bottle of water to see how many milligrams of calcium, sodium or potassium it contains, then you have enjoyed the results of analytical chemistry.

What about blood tests? Analytical chemistry, of course!

The development of analytical chemistry made it possible to detect the presence of substances in miniscule 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.

And although the popular television series sometimes exaggerate the technical capabilities within the reach of researchers, the truth is that the continuing development of analytical chemistry is, more and more, approaching reality to fiction.

Other Resources

  • Credits: Science Office / University of Aveiro Chromatography ( VIDEO )
    02.25.2013 ( 18 MB )DOWNLOAD

    Credits: Science Office / University of Aveiro

  • Credits: Science Office / University of Aveiro ICP ( VIDEO )
    02.25.2013 ( 4 MB )DOWNLOAD

    Credits: Science Office / University of Aveiro

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