They also know that little lies point to bigger lies.

No! Not necessarily they don't. This is all cop bullshit. If you don't remember the weather on your wedding day you're lying? I swear to God and hope to die I do not remember the weather on (either of) my wedding day(s). So I'm lying? What about? That I got married? Since I don't remember the weather I didn't get married? That is the most asinine lie detector test I've ever heard of.

Apparently FBI agents ask that question. They do believe, all cops do, that if you lie about one thing there are bigger lies behind it, "How can I believe anything you say now?", they will say to people they interrogate. So, Comey, can cops lie? You bet they can! Comey: When undercover FBI agents pose as a) drug dealers b) pedophiles c) hit men, they have to lie, no? To protect their cover. When they get in court and admit they lied to Scarface when they posed as a hit man, does that lie "point to bigger lies"? ABsolutely not.

And Comey is a lawyer too, a prosecutor, in addition to being a cop. He knows that that is not the law. The jury receives no instruction that "If you find the witness lied about one thing you can use that to conclude that nothing (s)he said is truthful." He also knows that a conviction will not be sustained if it is based entirely on a defendant's lies. In other words, in, say, a murder case, you cannot just put on the testimony of the medical examiner (to establish cause of death) and the defendant's lying statement to the detective. A provably false statement ("My name is John Doe" when it's really Kyle Killer) is not proof of guilt.

Sometimes a lie is confined to the one false statement. "Why did you give me a false name?" "Because I didn't want you to know my real name." The lie can be as meaningless to "bigger" lies as that. 

Those are just horseshit rules by James Comey.