How is what you're talking about here substantially different from any other criminal investigation? They were suspected of committing a crime, investigators got permission and looked into it, they found enough evidence to support a case, so they got a warrant, made arrests and collected evidence. That sounds pretty normal. Where does due process break down? It's not like the investigators tell you they're wiretapping your phone and give you a chance to argue against it when you're suspected of embezzlement.