"GOOD MORNING! My name is investigator Holmes. Do you mind answering a few simple questions?" If you open your door one day and are greeted with those words, stop and think! Whether it is the local police or the FBI at your door, you have certain legal rights of which you ought to be aware before you proceed any further.
In the first place, when the law enforcement authorities come to see you, there are no "simple questions." Unless they are investigating a traffic accident, you can be sure that they want information about somebody. And that somebody may be you!
Rule Number one to remember when confronted by the authorities is that there is no law require you to talk with the police, the FBI, or the representative of any other investigative agency. Even the simplest questions may be loaded and the seemingly harmless bits of information which you volunteer may later become vital links in a chain of circumstantial evidence against you or a friend.
Do not invite the investigator into your home! Such an invitation not only gives him the opportunity to look around for clues to your lifestyle, friends, reading material, etc., but also tends to prolong the conversation. And the longer the conversation, the more chance there is for a skilled investigator to find out what he wants to know.
Many times a police officer will ask you to accompany him to the police station to answer a few questions. In that case, simply thank him for the invitation and indicate that you are not disposed to accept it at that time. Often the authorities simply want to photograph a person for identification purposes, a procedure which is easily accomplished by placing him in a private room with a two-way mirror at the station, asking him a few innocent questions, and then releasing him.
If the investigator becomes angry at your failure to cooperate and threatens you with arrest, stand firm. He cannot legally place you under arrest or enter your home without a warrant signed by a judge. If he indicates that he has such a warrant, ask to see it. A person under arrest or located on premises to be searched, generally must be shown a warrant if he requests it and must be given a chance to read it.
Without a warrant, an officer depends solely upon your helpfulness to obtain the information he wants. So, unless you are quite sure of yourself, don't be helpful.
Probably the wisest approach to take to a persistent investigator is simply to say: "I'm quite busy now. If you have any questions that you feel I can answer, I'd be happy to listen to them in my lawyer's office. Goodbye!" Talk is cheap. But when that talk involves the law enforcement authorities, it may cost you, or someone close to you, dearly.