One really has to wonder how the Authorities responsible for investigating such crimes can do their job. Or do they have special powers that allow them to download and possess such material?

Presumably it's the same legal mechanism that lets the police confiscate drugs or stolen property without running round charging one another for possession of them. It's an interesting question, though: is it a special exemption for the police? If you perform a citizen's arrest for possession, and take the stuff from the offender, are you then in possession?

Peter