When the police suspect someone has committed a crime or knows something about it, one of the first things they will do is search for evidence. They might search their vehicle or property, for instance.
Typically, they will either need a warrant or the person’s permission to carry out the search. If they find something, they might be met with a look of surprise (legitimate or feigned) from the person and the words “It’s not mine.”
The police officers might believe the person is telling the truth, or they might not, but it doesn’t necessarily matter. The officers could still charge that person even if they accept they are telling the truth when they say the item is not theirs. In some cases, at least.
Constructive possession
Knowing about an item and having control over it can give the police grounds to charge a person based on the concept of constructive possession.
An example is a drug dealer who does not want to keep all his stock in his house. He persuades someone who owes him money to store some of the drugs for him. If that person knew they were drugs, then they could face charges. Another example could be a gun used in a shooting. The shooter asks a friend or lover to look after it for them until the heat has died down.
Sometimes people place items on the property of another person without their knowledge, such as slipping the gun under the seat of a friend’s car without saying a word about it. That should not result in charges, as even though the car owner could technically access it, they did not know it was there. Arguing that you did not have control over the item (such as if someone locked it in a safe on your property but took the only key) or that you never knew it was there could provide a potential defense for anyone facing charges due to evidence found on their property. Learning more about your defense options will be crucial if you find yourself in such a position.