So, in my real life, I'm a trial lawyer. I prosecute people who rape children and commit murder, and engage that sort of anti-social criminal behavior. Because of that, I'm pretty familiar (actually, extremely familiar) with the rules of evidence.
This post is for the purpose of talking about the rule against hearsay. I don't want to get all boring and legalish and stuff, but basically, the rule of hearsay provides that stuff that is said outside of court (i.e., to a witness who wants to repeat it in court) is sufficiently unreliable that it won't be allowed in court in front of the finder of fact (i.e., jury) unless it fits into an exception that gives it something that we call indicia of reliability. For our purposes, I'm just going to talk about regular old hearsay.