My question involves criminal law for the state of: Tennessee
Recently my friend borrowed my car to run an errand and forgot to turn his headlights on. Not surprisingly he was pulled over by the police. During the course of the stop the officer searched the car (I do not know the exact details of why or how the exchange of information occurred during the stop) and found a marijuana pipe, an 8th of mushrooms, and less than an 8th of pot, all of which are mine. My buddy spent the night in jail and my car was impounded. I have since got my car out of the impound and learned that my friend was charged with a misdemeanor.
I was recently questioned by the police with regards to my involvement in my friends arrest. I said the pipe was mine but that the drugs could be any number of people's as I lend my car out frequently to many different users, many of whom use drugs (I am a graduate student and have many other student friends and actually do let many of them borrow my car). During my questioning the police literally told me "we know the drugs aren't his [my friend's]" which is true as he has never done a drug in his life.
The police then threatened to have the bags of drugs fingerprinted and tie the evidence to someone forensically. I have yet to be given any charge.
What are the chances my friend's case gets dropped before court etc?
What are the chances they actually do fingerprint the drugs and find my prints? The drugs were touched by several different people including myself, but not including my friend who has actually been charged.
What are the chances I am charged with something? Either being charged with possession of paraphernalia (if they test the pipe for resin?) or with somehow being charged with possession of the drugs. Any advice is appreciated of course.

