Do you know where you were on Thursday evening at about eight o'clock last week, and who you were with, and what you were doing? Are you absolutely certain beyond any shadow of a doubt? Would you bet your life on it? If there is any possibility—no matter how slim or remote—that you could possibly be mistaken about such a thing, you are the kind of person who should never agree to talk to the police under just about any circumstances for as long as you live. And that includes practically everybody.