When a lawyer looks to defend a client accused of possession of a controlled substance, there are three main issues that come to the fore: type of drug, who had possession and how it was obtained by law enforcement.
Federal law has supremacy over state laws, so states have adopted the five-tiered federal schedule in the Controlled Substances Act of 1970:
Schedule 1 drugs are those that have no medical use and have a high potential for abuse such as heroin, LSD, peyote, methamphetamine and cocaine. Marijuana remains a federal schedule 1 drug despite decriminalization in many states and its approval for medical use in many more, including Illinois.
Schedule II drugs are those that have a high potential for addiction as well as abuse such as Oxycontin, Percocet, morphine, opium and codeine.
Schedule III drugs are those that have a lower potential for abuse but still may lead to addiction such as steroids, ketamine and medicine with codeine.
Schedule IV drugs are those that have a lower potential for abuse such as Xanax, Ativan and Klonopin.
Schedule V drugs are those that have limited quantities of codeine such as cough syrups.
Your defense starts with what kind of drug was found in your possession. Some drugs bring longer sentences than others.
Who had possession?
You have possession of something if it in your hand, on your person or if you have exclusive access such as if it were in a safe for which you are the only person with a key.
Without such indisputable proof of possession, prosecutors may rely on circumstantial evidence using constructive possession. Police can prove constructive possession if they can show that you knew about the controlled substance and had the capability to maintain and control it.
Your lawyer, on the other hand, will demand proof that the drugs belonged to you and not to any of the other people who access to the space where the drugs were found.
Search and seizure
Your lawyer may target procedural errors made by officials when you were arrested. The Fourth Amendment to the U.S. Constitution gives you the right to due process, including lawful search and seizure.
In many cases, law enforcement needs either your permission to search an area or a court-ordered search warrant. You can be frisked if police believe you are armed and they can search an area if they see an illegal item such as a weapon that may be unlicensed or drugs that may not have a prescription.
Law enforcement may also be shown to have engaged in entrapment. This occurs when they convince you to commit a crime you might not have otherwise committed.