How can they charge me with possession?
Actual possessionIf I am controlling the item physically I am in actual possession. An example would be if I am driving a car I am in actual physical possession of the car. I have what is called "dominion and control" over the property. I am the one who is deciding how the car is being operated.
Constructive possessionConstructive possession is not quite as clear as actual possession. I still have the ability to control the item. An example would be a gun sitting on the seat next to me in the car I am driving. I can pick it up and hold it or I can let it sit there. I am still able to exercise "dominion and control" over the gun. But then so could the passenger sitting on the other side of the gun. Possession can be shared.
I didn't know it was there - what now?This is what is referred to as "unwitting possession". I controlled the car and the glasses case sitting on the seat. The glasses case was not mine but I had borrowed the car so I had "dominion and control" over the glasses case. I had not looked inside the glasses case.
Here your lawyer would argue that the possession was "unwitting" which is a possible defense to possession.
Yes I had the drugs but only for a moment. "fleeting possession".Your passenger is afraid he will get caught with drugs when the cops pull you over so he hands you a baggy and says "here, hold this". You look at it and realize what it is and throw it out the window right away. The cop sees it come out the window and charges you with possession.
Your lawyer will argue that it is not yours, that it was thrust upon you and you disposed of it immediately. This is an example of "fleeting" or "transitory" possession which may be a defense to the possession.