Since he said nothing was his, and the friend admitted to all of it, why was he still charged, and will the charges stick in court?

Boyfriend doesn't have any prior record of anything. We know for a fact they weren't his and were definitely the friend's. Friend was also in possession of unlawful firearm. They were approached at a gas station, definitely profiled, and then the officers demanded to search vehicle. After declining right to search, second cop shows up with K-9 and claims dog alerted him. Very minuscule amount of heroin found, friend and is an opiate addict. The friend stated that all illegal items were in his possession, it was also the friend’s truck that items were found in.