Let’s say you suffered from back pain several months ago, but you have since recovered. To manage the pain, your doctor prescribed painkillers, and you have a few pills left over that you never needed.

One day, your neighbor slips and falls on some ice in front of her house. She’s in a great deal of pain, and asks you if she can have a couple of the pills. It may surprise readers to learn that handing over the pills would not be acting like a good neighbor. It would be a felony.

Not all drugs that lead to criminal charges are the types of substances we usually think of, like cocaine, methamphetamine and heroin. Drugs that have legal, medical uses, like Valium, oxycodone and Percocet, can nevertheless be considered illegal in certain circumstances. Police have the power to arrest you for drug possession, if they believe you do not have a prescription of an otherwise legal drug.

Perhaps even more serious would be felony distribution charges. The scenario we describe above could lead to such charges. Even giving your husband or wife a pill could end in your arrest, at least in theory.

As with every criminal investigation, there is a procedure police must follow in order to protect individuals’ civil rights. An illegal search of a person’s home or car may or may not turn up evidence of drug possession, but the evidence seized is “fruit of the poisonous tree.” This is vital to our criminal justice system, because it forces officers to respect our rights.