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Forensic Toxicology

The study of poisons and drug use in law enforcement

Taylor Bennett

on 15 March 2011

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Transcript of Forensic Toxicology

Forensic Toxicology Forensic toxicology is the study of poisons and drug use in the criminal environment. Forensic toxicologists have many techniques to identify drugs, poisons, and other substances within the human body. For analzying drugs and identifying unknown substances, there are two basic categories of tests: presumptive tests and confirmatory tests. Confirmatory tests are specific and can give the exact name of the drug, while presumptive tests can only give an idea of the category of the susbstance and not the actual name. Often presumptive tests are used so toxicologists will know what confirmatory test to use. For example, color tests are presumptive tests. They use chemicals or a mixture of chemicals to identify the category of drug. The Marquis color test, for example, uses formaldehyde and concentrated sulfuric acid. Heroin, Morphine and opium-based drugs will turn the compound purple. Amphetamines will turn it orange-brown. Another test, ultraviolet spectrophotometry, is also a presumptive test. It tests the substance's reaction to ultraviolet and infrared rays. A spectrophotometry machine gives off the ultraviolet and infrared rays. Then, it measures how much of each the substance absorbs and reflects. This will give a general idea of what the sbstance may be. However, a microcrystalline test is a confirmatory test that gives a very specific answer. Each drug has unique crystal pattern, which can be detected when a toxicologist puts a sample of the drug onto a slide with a chemical on it. These can be seen under a polarized light microscope. This is cocaine after a microcrystalline test. Picture from the Miami Dade police. A gas chromatology/ mass spectrometry test is also a confirmatory test. It uses a gas chromatograph, and a laser which splits the substance apart to figure out it's type. However, these tests do not identify poisons, which is another thing forensics scientists work with. There are 5 types of poisons; Corrosive, systemic, irritant, poisonous gas and poisonous food. Corrosive poisons detroy tissue that they touch. For example, sulfuric acid will dissolve the skin. Irritant poisons cause inflammation of the mucous membranes which line the air passages of the body. They hurt the nerve centers, stomach and intestines. Systemic poisons attack the nervous system and organs like the liver, kidneys and heart. Strychnine is a systemic poison. It's commonly used to kill rats. Sedatives are also systemic in large doses. Poisonous gas makes breathing difficult. Many of them irritate the eyes, lungs, nose, and skin. You can be poisoned by food if you eat certain chemicals or plants and their toxins. Insecticides and some shell fish can cause food poisoning. Toxicologists have ways of detecting these poisons in the human body. This involves an initial screening and final confirmation of compounds in biological samples. Whatever the substances is expected to be decides what test is used to confirm it. Compounds suspected of being metal are usually analyzed through the destruction of the organic matrix by chemical or thermal oxidation. However, this process destroys the original compound. Illicit and prescribed drugs, pesticides, natural products and industrial compounds are common nonvolatile substances. Screening methods for these include thin-layer chromatography, gas-liquid chromatography, and immunoassay. A second confirmatory test tends to be a must so that there are no false accusations made. During investigation, evidence must be collected and documented, along with the tests to be done on each one. The victims, if known, and the examiner must be named. The body's condition when found should be described and the date of death should also be recorded. Dates for when toxicological analyses were requested for each sample collected should also be recorded. The analyst that does the test must sign the page that explains the results and when the results were recieved. The highest concentration of poisons will always be at the site where they were administered. For example, a high concentration in the GI (gastrointestinal) tract and the liver may indicate that the substance entered the body through the mouth. Toxicologists must also know how poisons react in the body. They must know how certain poisons are absorbed, retained, and how they kill people. Toxicologists must also know how that body reacts when a poison enters. Forensic toxicologists do not work on their own, however; They work closely with pathologists, medical examiners and coroners. The toxicologists helps to identifies the cause and manner of death with the help of these people. The forensic toxicologist deals mostly with identifying the role of drugs, alcohol and poisons in a death. A toxicologist identifies a drug in blood and tissue samples and how much of it there is. Even though finding the cause of death is mainly the coroner's job, the toxicologist still plays an important role. The pathologist keeps in mind the information that the toxicologists provides in terms of the autopsy, the investigation, and the medical history of the case. Accuracy in this field is a must, as it has serious significance towards public health and safety. Reliable toxicology is essential. End Toxicologists provide information on drug kinetics and interactions, metabolism, adverse and idiosyncratic reactions, drug tolerance, postmortem artifacts, drug stability and other factors. Toxicology has been an important part of criminal investigation for as long time and has even freed innocent people from jail.
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