Yes, that would be considered a criminal act in most or all US states. Depending on the exact facts of the case it could be prosecuted as fourth-degree assault (misdemeanor), or it could fall under other statutes covering food adulteration or delivery of prescription drugs. I am answering in general terms and have no knowledge of what happened with Gates. A police investigation seems unlikely because so much time has passed (possibly exceeding the statute of limitations) and it would be hard to find admissible evidence.