In order to be charged with possession of a controlled substance in Pennsylvania, Possession can be found by proving: (1) actual possession; (2) constructive possession or (3) joint constructive possession. 
Actual possession occurs where an individual actually has the controlled substance or drug on his person, such as in his pocket or bag that he is carrying.  When contraband is not found on the defendant’s person, the Commonwealth must establish constructive possession. 
 Constructive possession is a legal fiction, a pragmatic construct to deal with the realities of criminal law enforcement. Constructive possession is an inference arising from a set of facts that possession of the contraband was more likely than not.  “The purpose of the constructive possession doctrine is to expand the scope of possession statutes to encompass those cases where actual possession at the time of arrest cannot be shown but where the inference that there has been actual possession is strong.”  “Constructive possession” is found where the individual does not have actual possession over the illegal item but has conscious dominion over it.  
In order to prove “conscious dominion,” the Commonwealth must present evidence to show that the defendant had both the power to control the firearm and the intent to exercise such control. 
 Joint constructive possession occurs where two or more people have joint control and equal access and thus all may constructively possess the contraband. Constructive and joint constructive possession can be inferred from the totality of the circumstances. However, mere presence at the scene is insufficient to prove either constructive possession or joint constructive possession of contraband.