If a suspect supplies a known fraudulent prescription and a police officer orders the pharmacist to fill it, does the factual impossibility defense apply for the suspect? This act was impossible to complete without the police officer.
For the record, factual impossibility is rarely a defense to a crime. In United States v. Thomas the court decided that men who believed they were raping a drunken unconscious women were guilty of attempted rape, even though the woman was dead at the time.
In this case there is no facts that made the offense impossible to commit. The suspect clearly submitted a false prescription and obtained the drugs he or she wished to obtain. There is no impossibility. Instead the police officer, as the saying goes, has the suspect "dead to rights".
This is not legal advice. Consult an attorney for that.