First off it is totally legal to take someone's trash. If it is the RA they have the right to enter without a search warrant and a police officer can only go in without a search warrant if the person gave consent which in this case he did. Because he allowed him to and because he would have found a broken piece with residue it is automatically collected as evidence. Those bastards took a really awesome gym bag of mine because it was collected for evidence...you probably won't see that trash can again so I hope your not too set on it. Anyway all in all it is legal to go through someone's trash if they have a search warrant or if the person allowed consent to enter the house. The only time a person can go through someone's trash without permission or a search warrant is if the trash is on the curb. Thats how a lot of big time drug dealers end up getting busted, so thats a good tip if anyone reading this is getting tailed by police. I think that answers your question, it was a bit ambiguous so let me know if it doesn't answer it.....oh yeah and as far as the second part no they can take the trash bag/can because it automatically becomes evidence.