In Texas what does the charge of possession of a dangerous drug mean?

It doesn't have to be on his person. His proximity to the drugs is an important affirmative link. Possession means care, custody, and control under Texas law. If the drugs were in plain view and he was the only person in the room with them, the State's argument is strong. He needs an experienced attorney representing him on this.

Your friend can be charged. The drug does not have to be on his person as the state will argue care, custody, control, etc. However, the case may be defensible. He needs to hire an experienced criminal defense attorney to represent him. Section 481.002 of the Health and Safety Code defines possession. "Possession" means actual care, custody, control, or management. Section 483.001 of the Health and Safety Code defines a dangerous drug. "Dangerous drug" means a device or a drug that is unsafe for self-medication and that is not included in Schedules I through V or Penalty Groups 1 through 4 of Chapter 481.

A dangerous drug is basically just a drug that requires a doctor's prescription to legally possess or use (which your friend presumably didn't have), but is not a contolled substance (something determined by whether it's listed in a section of the Health and Safety Code that has quite a few drugs listed out that are of greater concern for addiction and abuse--things like hydrocodone, Xanax, oxycodone, and morphine, in addition to cocaine, heroin, etc. Dangerous drugs are pretty much just the "leftover" prescription drugs they don't usually worry all thatuch about, but are still illegal to have without a prescription: antibiotics, most sleeping pills, and so on are dangerous drugs. And yes, your friend could very definitely be legally in possession without having them on his person. The example I always used with juries when I was a prosecutor is a pizza: if four or five of us are just sitting around talking with a pizza in a box in the middle of the table, ALL of us could potentially be charged with possession of the pizza if it were to turn out the Legislature made pizza illegal. NOT just the ones of us who actually had a slice in our hands, on our plates, or in our mouths when the cops show up. With the situation you're describing, it could get down to an analysis of things like whether the bottle was fingerprinted and the results, whether it was visible or covered by something, whether anyone admitted knowledge, how far away your friend was, whether any other belongings of your friend or others were found with the drugs, and so on. Your friend's chances of success with this will be a whole lot better with a good attorney, so that should be his first step.