Chemistry Of Forensic Techniques

The chemistry in forensic techniques is very important, and is a necessity in our world today. Forensics techniques are applied in many different ways. Although it is often forgotten, every person leaves behind a small part of their individual self wherever they happen to go without even realizing it. For this reason, forensics are often the key factor in providing evidence to solving crimes whether it is through fingerprinting, blood, or even a single strand of hair. Crime always has been and continues to be a significant problem all over the world. These crimes prove the importance of forensic science and have even sparked public interest in forensics within media and television. From shows such as Sherlock Holmes to CSI, this field of science and chemistry grasps the attention of all people, including children and students who do not have a great desire to learn. Not only does this increased interest give more people the opportunity to learn about science within school, but they also enjoy doing so. This interest in forensic science is not a surprise. Scientists have equipment, tools, chemicals, and techniques that are unbelievable. Forensic techniques have only continued to advance and improve within the past several decades, and scientists still continue to shock with amazing new developments.

There are dozens of different branches within forensics, but commonly, they all apply the use of chemistry in order to function properly. Forensic techniques have been used in analyzing criminal evidence since as long ago as the eighth century. During this time, identification through fingerprinting was beginning to be applied in China. In 1248, the first document to suggest science to solve a crime, Hsi Yuan Lu, was written, which provided information on how a person who died from being strangled, could be significantly identified from a person who has drowned. By the nineteenth century, developments increased. “This period saw the development of tests for blood, the invention of the Marsh test for arsenic in 1832, and studies on bullet ‘fingerprinting’ in the 1880s” (Newton 6).

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In this period, the first valuable information for analyzing human blood was discovered by Christian Friedrich Schonbein, who used the chemical, hydrogen peroxide along with bloodstains, discovering that these two combined caused a type of foaming. This was a huge breakthrough because it identified the difference between a stain of blood and an everyday stain. Blood is arguably the most important proof in any violent crime scene. This type of forensic science involving the study of blood and fluids is referred to as serology.

Although the beginning studies of serology were in the 1860s, advancements and research did not progress much until the more recent, 20th century. For a time, doctors believed that all blood was the same, and believed it could be transferred from person to person. This was proved wrong because of the discovery of the chemistry of blood, and the different blood types. Blood is a mix of cells, with the most important as red blood cells, which are behind the act of oxygen being transferred to lungs. These cells are covered with different molecules, with different functions. These form a pattern, which vary from person to person, and cause a person’s body to fight off any pattern they are not familiar with. “These attacking molecules are antibodies. For each specific molecule unfamiliar to a person’s immune system -molecules known as antigens- the immune system will produce a specific antibody” (Newton 35). These chemical patterns and antigens form the various blood types that scientists are now very familiar with today.

But how does this information help forensic scientists to identify criminals and investigate crime scenes? There are many different ways to apply chemistry in crime scene investigations, including, “Genetic fingerprinting , the obtaining or comparing of genetic fingerprints for identification; the comparison of DNA in a person's blood with that identified in matter found at the scene of a crime, etc” (Jeffreys 1). If a bloodstain is discovered within a crime scene, and it is discovered to be type A, that narrows the suspect list significantly. This is known as the ABO system in forensic serology.

Like serology, fingerprinting plays a large role in identifying criminals and individuals in general. Fingerprinting has been used for centuries, as far back as the third century by the Chinese. However, studies did not begin until the 1960s, when Nehemiah Grew discovered the uniqueness in the designs on the tips of each person’s fingers. Fingerprints are the only part of a person’s entire body that is not smooth. Fingerprints are entirely individual and are not repeated among any two people, even if those two people are twins. Another interesting trait of fingerprints is the fact that a person’s will never change throughout their lifetime. However, the process of DNA fingerprinting is also made difficult because of the uniqueness of each person’s fingerprints. This makes it more difficult to be sure that two compared sets are identical.

DNA fingerprinting takes multiple steps in order to be complete. The strands of DNA that are used in this process are known as VNTRs, which is an acronym for variable number tandem repeats. They include the “variable number” in the name, because the pattern of the DNA will repeat over and over again in the strands. Although DNA is already tiny, scientists begin the process by cutting the DNA into even smaller pieces. They are able to do so through the use of chemicals known as enzymes. “Enzymes are special proteins that have very specific functions. Restriction enzymes can find specific DNA sequences and break DNA apart at that sequence. These enzymes are derived from bacteria that use them to break up the DNA of any organism they might invade” (Hunter 29). The second step the scientist takes is separating these pieces from each other, and categorizing them based on their various sizes. These are then placed on X-ray film, which then provides an image of the pattern of the DNA pieces. However, before placed on the X-ray, they must be secured by a strong, thin membrane, otherwise they will not be preserved for a long time and can easily be destroyed. When a forensic scientist views the image of the DNA of a suspect and compares this image to one of DNA from a crime scene, this can either prove the person guilty or innocent, providing a strong form of evidence. Although this process is pricey and is not very efficient, it is helpful and accurate when it comes to a court case or to determining the truth behind an unsolved crime.

This is not the only method that scientists have discovered in testing fingerprints. One of the most influential tests that has been developed in fingerprinting is the chemical test, which relies on a chemical reaction to change color.

In this test, silver nitrate covers the surface that is being tested for fingerprints, and it is then exposed to a light source, whether it is natural or artificial. This causes the reaction to take place and as a result, the fingerprints become evidently seen on the tested surface within a short amount of time. This method is very different compared to the previously mentioned method, but is just as effective. This method is also more efficient. Forensic scientists continue to conduct research and seek new ways to test fingerprints as well as seeking to improve existing processes.

Although it is very different from serology and fingerprinting, toxicology is similar to these two types of forensic techniques because it is also a very important way of establishing crimes. Toxicology is defined as the “biological, physiological, and pharmacological properties of drugs and poisons to the medical and legal implications associated with their abuse or medical administration” (Newton 65). Blood alcohol concentration is the percentage of alcohol in the bloodstream and in most states, the legal limit is 0.08. Drunk driving is the cause behind thousands of accidents each year, in which at least one of the drivers involved had a blood alcohol concentration higher than 0.01. Toxicologists are responsible for determining whether someone has been drinking and how much they have drank. They also have the responsibility of proving whether a person, living or dead, has consumed a poisonous chemical or a drug, and to determine what drug or poison this person consumed. These poisonous chemicals can vary from basic cleaning supplies, to advanced poisons such as cyanide and strychnine.

What makes alcohol “alcoholic”? This would be the organic chemical, chemical formula CH3CH2OH, which is more commonly known as ethanol. When alcohol is consumed, most of it makes its way into the bloodstream. This is why alcohol level is tested in blood alcohol concentration. Alcohol in blood is identifiable within a couple minutes of it being consumed.

Carbonation also plays a factor in a bloodstream with alcohol. If the alcoholic drink has bubbles, this raises the rate of the alcohol being absorbed into the bloodstream. However, a person’s body uses both the chemical process of oxidation and the process of excretion to get rid of this alcohol over a period of time. “Oxidation takes place in the liver, where the enzyme alcohol dehydrogenase, in conjunction with the coenzyme nicotinamide adenine dinucleotide (NAD), converts ethanol first to acetaldehyde, then to acetic acid, and eventually to carbon dioxide and water” (Newton 67).

Blood alcohol concentration became intriguing to forensic scientists in the mid-1930s with the Eighteenth Amendment. The amendment prohibited the sale and consumption of alcohol in the United States. The revoking of this amendment created many problems in the United States and led to an increase in abuse of alcohol. The first testing for alcohol came to be testing a person’s breath. This came with the “Drunkometer”, which was a test created by a biochemist by the name of Rolla Harger. Through this test, a person breathed into a balloon. The air that is held within this balloon is then released into a chemical solution. This chemical solution would change color according to the amount of alcohol present within the air released. This reaction that takes place is ethanol reacting with potassium permanganate.

In this reaction, the red-orange dichromate ion converts to green chromium ion. With the increased amount of ethanol, the more complete the reaction between the two. This reaction provides the blood alcohol concentration level and is easily shown. This system is used all over the world today, including within many schools, police departments, companies, and businesses.

Along with testing for alcohol, a toxicologist is also responsible for testing for the presence of poison and drugs within a person’s body. Over the last couple decades, use of illegal drugs has increased significantly, even among children as young as 12 years old. “According to the 2005 National Survey on Drug Use and Health produced by the Substance Abuse and Mental Health Service Administration, 19.7 million Americans over the age of 12 had reported using an illicit drug during the previous month” (Newton 81).” This information is important to toxicologists and forensic scientists because these drugs are illegal, are often related to crime and criminals, and often are a frequent cause of death. The presence of drugs is also important because many companies use drug testing to determine who they want as their employees. Many schools around the world also put drug testing to use by testing students and athletes.

In order to determine whether a drug is involved, two tests must take place. The first is known as a screening test, which limits the number of drugs or poisons that may be present, but does not determine the exact drug or poison that is present. This is where the confirmatory test plays its part. This test is used to find the exact chemistry of a substance and determine whether a substance is actually in a sample.

Poisons can be much more difficult to identify compared to drugs because there are over 10,000 that are known to man. Out of these 10,000 different poisons, there are only two categories that they are identified in. Poisons are referred to as either organic, or inorganic. There are hundreds of different testing methods, many of which are specific to a certain poison. One of these methods includes the Forrest test, which is a screening, rather than a confirmatory, test. This test is made exclusively for the poison imipramine. However, similar techniques to this one are used in other poison methods. Imipramine is a tricyclic organic compound, and is often used to battle depression. Forrest may sound complicated to create, but is another test that is simply meant to change color through a chemical reaction to prove and highlight the presence of another substance. “Forrest reagent is made by mixing 25 milliliters of a 2 percent aqueous solution of potassium dichromate (K2Cr2O7) with equal volumes of concentrated sulfuric acid, concentrated perchloric acid (HClO4), and concentrated nitric acid” (Newton 89). This test is performed by stirring this substance along with sample urine. If the results are positive, it will change from a yellow-green color, to a deeper dark green-blue. Tests very similar to this one are used to reveal the appearance of poisons such as desipramine, trimipramine, and clomipramine. Once this screening test is carried out, it is follow by a more powerful confirmatory test. This will assure that the results are accurate and no mistakes have been made. Toxicology has had one of the greatest impacts in forensic science and has made a great amount of contributions. There are now hundreds of chemical tests to find traces of alcohol, drugs, and poisons that early scientists never even imagined they would ever have.

In conclusion, chemistry in forensic techniques has had a huge impact in our world, and continues to today. Without these processes, scientists would not be able to discover the advanced information they now have. Also, our justice system would not be nearly as strong and many criminals may have gotten away with terrible things they have done, while many innocent people may have been accused because of the lack of evidence to prove people innocent or guilty. Serology, Fingerprinting, and Toxicology are only three of the many types of forensic techniques, and all of them are important and beneficial. Scientists everyday continue to search for new ways to apply chemistry in forensic techniques, and surely they will continue to shock the world with their advancements and amazing techniques.

Works Cited

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