What is Forensic Chemistry - Jefferson County Public Schoolsboe.jeff.k12.wv.us/cms/lib02/WV01001913/Centricity/Domain/1234/Ch 9... · Forensic Chemistry 1 8-Criminalistics, 10e Richard
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Introduction• A drug can be defined as a natural or synthetic
substance that is used to produce physiological or psychological effects in humans or other higher order animals.
• Narcotic drugs are analgesics, meaning they relieve pain by a depressing action on the central nervous system. This effects functions such as blood pressure, pulse rate, and breathing rate.
• The regular use of a narcotic drug will invariably lead to physical dependence.
• The most common source for these narcotic drugs is opium, extracted from poppies.
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Marijuana• Marijuana is the most controversial drug in this class
because its long-term effects on health are still largely unknown.
• Marijuana refers to a preparation derived from the plant Cannabis.
• The chemical substance largely responsible for the hallucinogenic properties of marijuana is known as tetrahydrocannabinol, or THC.
• The THC content of Cannabis varies in different parts of the plant, generally decreasing in the following sequence: resin, flowers, leaves, with little THC in the stem, roots, or seeds.
• The THC-rich resin is known as hashish.
• Marijuana does not cause physical dependency, but the risk of harm is in heavy, long-term use.
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Depressants• Depressants are another class of drugs.
• Depressants are substances used to depress the functions of the central nervous system.
• Depressants calm irritability and anxiety and may induce sleep.
• These include alcohol (ethanol), barbiturates, tranquilizers, and various substances that can be sniffed, such as airplane glue, model cement, or aerosol gas propellants such as freon.
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Stimulants• Amphetamine and methamphetamine, often
injected intravenously, cause an initial “rush,” followed by an intense feeling of pleasure.
• This is followed by a period of exhaustion and a prolonged period of depression.
• Cocaine, extracted from the leaves of Erythroxylincoca, causes increased alertness and vigor, accompanied by the suppression of hunger, fatigue, and boredom.
• Crack is cocaine mixed with baking soda and water, then heated.
• Crack is often smoked in glass pipes, and, like cocaine, stimulates the brain’s pleasure center.
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Club Drugs
• The term club drugs refers to synthetic drugs that are used at nightclubs, bars, and raves (all-night dance parties).
• Substances that are often used as club drugs include, but are not limited to, MDMA (Ecstasy), GHB (gamma hydroxybutyrate), Rohypnol (“Roofies”), ketamine, and methamphetamine.
• GHB and Rohypnol are central nervous system depressants that are often connected with drug-facilitated sexual assault, rape, and robbery.
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Club Drugs
• Methylenedioxymethamphetamine, also known as MDMA or Ecstasy, is a synthetic mind-altering drug that exhibits many hallucinogenic and amphetamine-like effects.
• Ecstasy enhances self-awareness and decreases inhibitions; however, seizures, muscle breakdown, stroke, kidney failure, and cardiovascular system failure often accompany chronic abuse.
• Ketamine is primarily used as a veterinary animal anesthetic that in humans causes euphoria and hallucinations.
• Ketamine can also cause impaired motor functions, high blood pressure, amnesia, and mild respiratory depression.
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Preliminary Analysis
• Faced with the prospect that the unknown substance may be any one of a thousand or more commonly encountered drugs, the analyst must employ screening tests to reduce these possibilities to a small and manageable number.
• This objective is often accomplished by subjecting the material to a series of color tests that will produce characteristic colors for the more commonly encountered illicit drugs.
• Microcrystalline tests can also be used to identify specific drug substances by studying the size and shape of crystals formed when the drug is mixed with specific reagents.
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Confirmational Determination
• Once this preliminary analysis is completed, a confirmational determination is pursued.
• Forensic chemists will employ a specific test to identify a drug substance to the exclusion of all other known chemical substances.
• Typically infrared spectrophotometry or mass spectrometry is used to specifically identify a drug substance. Sometimes chromatography can also be used
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Introduction• Toxicologists are charged with the responsibility
for detecting and identifying the presence of drugs and poisons in body fluids, tissues, and organs.
• Toxicologists not only work in crime laboratories and medical examiners’ offices, but may also reach into hospital laboratories and health facilities to identify a drug overdose or monitor the intake of drugs.
• A major branch of forensic toxicology deals with the measurement of alcohol in the body for matters that pertain to violations of criminal law.
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Alcohol Levels• Alcohol appears in the blood within minutes after it has
been taken by mouth and slowly increases in concentration while it is being absorbed from the stomach and the small intestine into the bloodstream.
• When all the alcohol has been absorbed, a maximum alcohol level is reached in the blood; and the postabsorption period begins.
• Then the alcohol concentration slowly decreases until a zero level is again reached.
• Factors such as time taken to consume the drink, the alcohol content, the amount consumed, and food present in the stomach determine the rate at which alcohol is absorbed.
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Alcohol Levels
• Elimination of alcohol throughout the body is accomplished through oxidation and excretion.
• Oxidation takes place almost entirely in the liver, while alcohol is excreted unchanged in the breath, urine, and perspiration.
• The extent to which an individual may be under the influence of alcohol is usually determined by either measuring the quantity of alcohol present in the blood system or by measuring the alcohol content in the breath.
• Experimental evidence has verified that the amount of alcohol exhaled in the breath is in direct proportion to the blood concentration.
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Breath Testers
• Breath testers that operate on the principle of infrared light absorption are becoming increasingly popular within the law enforcement community.
• Many types of breath testers are designed to capture a set volume of breath.
• The captured breath is exposed to infrared light.
• It’s the degree of the interaction of the light with alcohol in the captured breath sample that allows the instrument to measure a blood alcohol concentration in breath.
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Gas Chromatography Testing• Gas chromatography offers the toxicologist the
most widely used approach for determining alcohol levels in blood.
• Blood must always be drawn under medically accepted conditions by a qualified individual.
• It is important that a nonalcoholic disinfectant be applied before the suspect’s skin is penetrated with a sterile needle or lancet.
• Once blood is removed from an individual, its preservation is best ensured when it is sealed in an airtight container after an anticoagulant and a preservative have been added and stored in a refrigerator.
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Alcohol and Law• The American Medical Association and the
National Safety Council have been able to exert considerable influence in convincing the states to establish uniform and reasonable blood-alcohol standards.
• Between 1939 and 1964 a person having a blood-alcohol level in excess of 0.15 percent w/v was to be considered under the influence, which was lowered to 0.10 percent by 1965.
• In 1972 the impairment level was recommended to be lowered again to 0.08 percent w/v.
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Alcohol and Law• Starting in 2003, states that have not adopted the
0.08 percent per se level will lose part of their federal funds for highway construction.
• To prevent a person’s refusal to take a test for alcohol consumption, the National Highway Traffic Safety Administration recommended an “implied consent” law.
• Adopted by all states by 1973, this law states that the operation of a motor vehicle on a public highway automatically carries with it the stipulation that a driver will submit for a test for alcohol intoxication if requested or be subject to loss of the license.
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Role of the Toxicologist• Beyond the analysis of alcohol, the toxicologist is
confronted with a maze of drugs and poisons.
• The toxicologist is originally presented with body fluids and/or organs and is normally requested to examine them for the presence of drugs and poisons.
• Without supportive evidence, such as the victim’s symptoms, a postmortem pathological examination, or an examination of the victim’s personal effects, the toxicologist is forced to use general screening procedures with the hope of narrowing thousands of possibilities to one.
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The Analytical Scheme• The forensic toxicologist must devise an analytical
scheme that will successfully detect, isolate, and specifically identify toxic drug substances.
• Once the drug has been extracted from appropriate biological fluids, tissues, and organs, the forensic toxicologist can proceed to identify the drug substance present.
• Drug extraction is generally based on a large number of drugs being either acidic or basic.
• The strategy used for identifying abused drugs entails a two-step approach: screening and confirmation.