The Chemistry of Forensic Science


Forensic Science is the application of science to criminal and civil laws, and is quickly becoming the new and modern way to solve mysteries and homicides. A forensic chemist can determine the composition and nature of materials with hours of scientific methods, including the examining of fingerprints and blood splatter located at a crime scene. There are 4 different kinds of forensic scientists: forensic serologists examine body fluids, forensic pathologists examine human remains, firearms technicians classify and test firearms and explosives, and forensic chemists determine the composition and identity of materials. Forensic specialists can even testify in court using evidence they obtain, often deciding whether or not the witness or suspect are lying. I chose forensic science as my subject because I’m interested in possibly pursuing a career involving forensic science and the solving of homicides preferably. Forensic science hasn’t personally affected my life, but it has affected many others in the world who have witnessed such tragedies as the death of a loved one or the rape of an innocent. Forensic science is the only sure way to know whose blood is whose and whose fingerprints are located at a crime scene.

Composition of ...

A forensic scientist has access to various tools that can be used to solve even the most tough-cracking mysteries. The first tool a forensic scientist can use is an Alternate Light Source, also known as an “ALS”. An ALS is a special flashlight that can reveal fingerprints, blood, saliva, and other pieces of evidence that are invisible to the naked eye. It consists of a light bulb, a filter that enables all but the selected wavelengths of light to be screened out, a device to deliver the light to the area being examined, and Fluorescence. Forensic chemists can also use a substance that has a similar use as the ALS; Cyanoacrylate Vapors. Applying Cyanoacrylate to interesting spots at a crime scene can reveal fingerprints not visible to human eyes. Yet another fingerprint revealing compound is Ninhydrin. Ninhydrin, which has C9H6O4 as its formula, makes fingerprints turn purple, allowing forensic scientists to photograph the evidence. Chromatography can also be used to obtain DNA samples that can be compared to evidence in a case and can help detectives narrow down the list of suspects. James Marsh created a forensic method to find out if a liquid has traces of arsenic in it, to decide if a man poisoned his father. Combine a sample of the suspected poisoned liquid, like a cup of coffee, with sulfuric acid, which has the chemical formula H2SO4, and Zinc, resulting in Arsine gas, which has the formula AsH3. Burning the gas causes it to decompose into pure metallic arsenic, which, when passed to a cold surface, will appear as a silvery-black deposit. If there’s arsenic there, then there was arsenic in the liquid sample, meaning the suspect is guilty. This is known as the Marsh test and tests similar to it are used now during modern times.

Main Chemicals, Compounds, Components

Cyanoacrylate Vapors have the general formula of CH2=C(CN)CO2R, which varies depending on the specific type of vapor. Ninhydrin has the formula of C9H6O4. Both Ninhydrin and Cyanoacrylate Vapors are natural while the ALS is mostly man made, with a touch of natural fluorescence.

Chemistry's Role

An Alternate Light Source uses fluorescence, which is a type of luminescence. Fluorescence is brought about by absorption of photons in the singlet ground state promoted to a singlet excited state. As the excited molecule returns to ground state, it involves the emission of a photon of lower energy, which corresponds to a longer wavelength, than the absorbed photon.When forensic specialists use Cyanoacrylate, it is warmed to create fumes that react with the invisible fingerprint and moisture in the atmosphere to form a white polymer on the fingerprint ridges. Once amino acid containing fingerprints, formed by sweat secretions which gather on the fingers unique ridges, are treated with a ninhydrin solution, they’ll turn purple and visible.

Background Research

Forensic scientists are expert witnesses in both criminal and civil cases and can either work for the prosecution or the defense. There were many early methods that slowly evolved into the forensic methods known by many today. One of these methods is from early China and India; suspects placed dried rice or rice powder in their mouths and spit it out. It was assumed that whoever was guilty would produce less saliva because of their lies, causing the rice to stick to their mouth. In ancient middle-eastern cultures, suspects were forced to lick hot metal rods briefly. If their tongue is more burnt than the other suspects, their mouth is drier, meaning that they’re most likely lying. Another forensic method was used by Henry Goddard at Scotland Yard, who was the first to use bullet comparison to find a killer. He noticed a flaw in the bullet that killed the victim and was able to trace it back to the mold used in the manufacturing process. After that, the bullet was traced to a buyer.Early methods like these were eventually modified to be used by modern forensic scientists.


Forensic specialists perform analyses to identify materials and learn the nature of evidence in crimes

A forensic chemist can determine the composition and nature of materials and can even predict the source of the evidence

There are 4 different kinds of forensic scientists: forensic serologists examine body fluids, forensic pathologists examine human remains, firearms technicians classify and test firearms and explosives, and forensic chemists determine the composition and identity of materials

Forensic scientists are tasked with the collection, preservation, and analysis of scientific evidence, like DNA, during the course of an investigation

Some methods used by forensic chemists to solve crimes are high-performance liquid chromatography, gas chromatography-mass spectrometry, atomic absorption spectroscopy, Fourier transform infrared spectroscopy, and thin layer chromatography

Forensic chemists often testify in court and use the evidence they found to refute or confirm a witnesse’s claim

Forensic experts can examine blood evidence left behind and draw conclusions to where and how the blood was shed

DNA found at crime scenes can be used to link perpetrators to the crime and to develop new leads

Fingerprints found at crime scenes can be used to link suspects to the crime

Forensic scientists can perform chemical analysis in their labs to detect illegal drugs

Components of Alternate Light Source

Formula of Ninhydrin

Information on Cyanoacrylate

Chemistry of Fluorescence

About the Author

Clark Duncan has been called the “coolest person you’ll ever meet” by many and often goes by the nickname “Little C”. He’s not just funny, he’s also dashingly handsome as well! When he sees you, he’ll often refer to you as “homie” or “homeslice”. If he calls you one or both of those things and offers to do his signature handshake with you, I suggest that you do it before he refers to you as “a muggle” (whatever that’s supposed to mean…). He attends Billings Senior High School as a junior, but claims that he should have graduated four years ago because of his superior intellect. He has two brothers, Hayden and Levi Duncan, who question their kindred to him everyday. They’re probably just mad that he claims that he’s too cool for them. Clark wakes up every morning with perfect hair and doesn’t even have to get in the shower to smell good. In his spare time, Mr. Duncan sits in the same position for extended hours, lays down on his bed before accidentally falling asleep during the afternoon, and browses Facebook with minimal curiosity. To top it all off, Clark plans on going to college after high school for various reasons, possibly majoring in criminal justice, with a minor in literature/writing.