If you accept or buy something that is stolen and you are unaware that it is stolen you are not breaking the the law because you didn`t "knowingly accept stolen property".However if the person tells you it is stolen and you still accept it or purchase it you are now "knowingly" committing a crime.I have a very good friend that has been a judge for many years and I ask him about this when we played golf yesterday so it is straight form a judges mouth.