To answer your question...Yes....while no one can force "him" to take a polygraph examination.  It would make no sense whatsoever to force someone to take such a test if they did not want to.  CID is offering him a chance to help prove his professed innocence.  Were he to pass the test, the convening authority MIGHT take that into consideration, but a lot has to do with the credibility of the person who identified "your friend" to the authorities and/or any other evidence in the case. As far as being charged?...makes no difference if he takes the examination or not.  While the polygraph is not admissible. per se, under the MCM, there have been cases when a judge (or convening authority) sitting alone and  weighing ALL of the evidence has dismissed charges where a suspect took and passed a properly administered government conducted polygraph examination.  I have to tell you though, I found your comments interesting where you said that "your friend" has never been caught possessing or selling...and that he is most likely going to fail...were those slips of the tongue?..or do these statements reflect that this time he was caught. Your "friend", it would seem might be better off trying to negotiate a plea.  You seem to feel, as I do, that he will fail the exam.  Hopefully he isn't planning on doing anything foolish like atttempt countermeasures? Why make things worse.