Forensic Drug Analysis

The main difference between forensic toxicology and forensic drug analysis is the sample types. Toxicologists work with drugs and poisons found in the blood, bodily fluids, and tissues, while forensic chemists work with the drugs and poisons before they are ingested. In a typical local or state crime laboratory drug cases represent the largest caseload and work that the laboratory performs. Of those cases the largest single group of cases usually involves marijuana.

The job of the forensic drug analyst is to identify any illegal substances found in exhibits or to prove conclusively that no illegal drugs or substances are present. This is accomplished by successive classification followed by definitive identification. But to understand this process it is helpful to answer two fundamental questions: First, what is a drug? Secondly, how exactly does a chemist classify a drug?


It has already been shown that everything can be a poison, but the same is not true of a drug. A drug can be a poison, but not all poisons are drugs. A drug is a substance that when ingested is capable of inducing a change in the body's chemistry. Drugs are used to treat or prevent disease, to reduce pain, to promote sleep, and so on. Medicines are combinations of drugs and inert ingredients. For example, an aspirin tablet that contains nothing but aspirin is a drug, while a tablet taken to treat the symptoms of a cold is a medicine, because it contains separate ingredients for a runny nose, congestion, coughing, aches, sore throat, and a fever. The terms drug and medicine are often used interchangeably, despite this distinction.

Obviously not all drugs or medicines are illegal. There are two factors that are important when a government agency decides if possessing a drug is illegal. First, if the drug has a potential to be abused, then it is likely to be controlled in some way, as abuse could cause harm. Second, if a drug has a legitimate medical use, then it must still be available to doctors and pharmacists to provide to patients who need it. The government must weigh the legitimate needs and uses of a drug against its ability to be abused and to cause harm when deciding how to regulate it.

The definition of drug abuse changes over time and differs among societies. Cocaine was once an ingredient in Coca-Cola, LSD was used in psychotherapy and by the CIA, and methamphetamine was issued to American soldiers during World War II. All three drugs are regarded as dangerous today, and they are no longer used in these ways. Meanwhile, the active ingredient in marijuana has been found to be useful in treating glaucoma, anorexia, and the nausea associated with chemotherapy. A drug, Marinol (dronabinol), now exists that contains the active ingredients of marijuana. The list of illegal or controlled drugs is therefore flexible and evolves. What tends to remain the same is the methods used to group and classify drugs.


Chemists usually describe drugs based on their chemical properties. Some drugs, such as aspirin, are acidic. If an aspirin tablet is dissolved in water, the pH of the water will become slightly acidic, comparable to vinegar or diluted lemon juice. The active ingredients in marijuana are also slightly acidic. Most drugs are weak bases and as a result have a bitter taste. Caffeine, found in coffee, tea, and many sodas, is a basic

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