First, it doesn't exist in Germany. Second, that applies to illegally obtained evidence. For example, if (in the US) the police tortured someone/broke in somew

First, it doesn't exist in Germany. Second, that applies to illegally obtained evidence. For example, if (in the US) the police tortured someone/broke in somewhere without a search warrant to obtain the MAC, then the fruit of the poisonous tree doctrine would likely apply to the evidence found as a result of the MAC address connection. Finding additional evidence starting from a vague lead ("the robber was wearing black clothes") is not something illegal, it's good police work.