Let's take a case example: A police officer is on his way to work and so not yet in uniform. While standing at a crowded bus stop, he overhears someone on his cell phone, softly discussing where and when he will be meeting a friend to purchase narcotics. A bit surprised, the officer steps a little closer to the person and activates a small digital recorder, and records the one side of the conversation that can be heard standing next to the person, who is so engrossed in his conversation that he never notices. The officer relays this information to narcotics officers, who wait at the location, a public restroom, in civilian clothes. The person arrives and the transaction is conducted in one of the restroom stalls. The narcotics officers observe the transaction through the gap between the door and the wall of the stall. The officers then arrest both parties to the transaction.

Prepare an argument to be made to the judge, on behalf of either the prosecutor or the defense, as to whether the arrest is legal or not. Is the overhearing of the call permissible? Is recording it? Is spying on two people conducting a transaction in a public restroom stall permissible?