Jerry Whorebach wrote:

First, the cops would ask about the conversation before the suspect knew how they were privy to it, hoping he would admit to typing those words. Later, provided the log was allowed into evidence (by that one incompetent/sexist judge?), the prosecutor would ask the defendant - under oath - if those were his words, and it would come down to the jury to decide if he's lying.

At least, that's how it works on Law & Order.