There were some central air units stolen from a couple of houses under construction by my house. The police say as a "Courtesy Check" they walked into my backyard to see if mine was also taken. I was not home during this time and had given no permision for them to enter my backyard. When they did enter my backyard they discovered a Marijuana plant and took it, they then went through my mailbox to get my name. When I returned home they surrounded myy truck and asked me if I was "Mike"; information I am assuming they gained from my mailbox while waiting on me. They had no search warrant and wanted to search inside my house for more plants, I gave them permision to enter and only look for plants in the closests and other rooms where plants could be grown; they came up with nothing. Can they legaly go into my backyard without probable cause or a search warrant and go through my mailbox to gain info about me. Also, can the plant plant they did find be admisable in court considering they had no reason to enter my backyard or had a warrant to do so and sieze the plant.