There's going to be an interesting Supreme Court case when the police bother to recover a Gmail session cookie from someone's phone or laptop and use it to dive into their email. My guess is the Gmail account owner will win, because when you seize my housekey during an arrest, you do not get to search my house.
The reason this hasn't happened already, though, is that the police aren't generally trawling through the Gmail accounts of drug suspects. They have more drug suspects on eyewitness and hand-to-hands than they can deal with; read _Cop in the Hood_ for examples of state prosecutors refusing to pursue cases because drugs seized from suspects "could, for all the apprehending officer knew, have been an Oreo cookie".
The reason this hasn't happened already, though, is that the police aren't generally trawling through the Gmail accounts of drug suspects. They have more drug suspects on eyewitness and hand-to-hands than they can deal with; read _Cop in the Hood_ for examples of state prosecutors refusing to pursue cases because drugs seized from suspects "could, for all the apprehending officer knew, have been an Oreo cookie".
This is mostly just a fun topic to chatter about.