Say a law enforcement pulls a driver over for a traffic infraction, such as speeding. During the traffic stop, the officer develops a reasonable suspicion there may be drugs involved in the situation. An inspection uncovers a baggy of an illegal substance.
Does this mean the driver will end up with a conviction for drug possession? It depends.
Two types of possession
The prosecutor will have the responsibility of proving the drugs belonged to the driver to achieve a possession conviction. If the officer found the drugs on the driver's person, such as in his pocket, that is actual possession and is likely the only proof necessary to convince a judge.
Constructive possession is a different matter. As an example, maybe the baggy of drugs was not in the driver's pocket, but somewhere in the vehicle. Now the prosecution must turn to the circumstances of the situation to find evidence strong enough to convince the judge the driver possessed the substance.
Perhaps the drugs were between the passenger seat and the center console. In that case, there may be reasonable doubt the drugs belong to the driver, as anyone else who rode in the car could have left them there. It could even have been that a passenger accidentally dropped them from a pocket or purse, and the driver never knew the baggy existed.
But what if the officer is conducting a legal search and discovers the locked glove box? She orders the driver to open it, so he complies, using a key from his keyring. The baggy the officer pulls out the glove box was under the control of the driver, so the judge may reasonably infer he owned the drugs.
It is important to keep in mind that, regardless of the driver's perception of the circumstances, there may be other factors surrounding the situation that could contribute to a strong defense.