Who gets to decide when someone is lying?

[Clueless Morgan]

I'm taking a Coursera.org class on argumentation and was immediately embroiled in the discussion forum thread called "The Bible/Koran is unreliable evidence to support the claim "Christian God/Allah exists""

To make a long story short, the thread devolved into a discussion of what is reliable evidence, specifically the reliability of anecdotal evidence versus empirical/scientific evidence, and I presented the following argument:

(1) Evidence that is based on lies or omissions of known relevant contrary facts is not reliable evidence.
(2) Anecdotal evidence could be based on a lie or the omission of known relevant contrary facts.
(3) It is irrelevant whether the person relaying the anecdote is cognizant of whether their anecdote contains a lie or omission of known relevant contrary facts.
_________________________________
.:. (4) Anecdotal evidence is not always reliable.

To which a fellow student responded:

I don't know if you argument could be valid but judging by your initial premises ... which is wrong in fact ... who gets to determine what are lies or omissions ... are these the same words or different ... are omission lies ... or the other way round? ... I'm guessing it is not a sound argument although your conclusion is true.

I responded to other points in his post in thread, but the relevant portion I wish to discuss here is in bold above.

My response to him on this point was as follows:

Linguistically, lies and omissions are defined by the English language (see below).

It seem that what you're getting at, though, is "who gets to make the determination that someone is lying or omitting relevant facts?" I suppose the best answer to that is "the person who discovers the lie or omission has taken place." Unfortunately, this means that a lie can persist for years, decades, even centuries without being uncovered. Piltdown Man, for instance, was presented as the remains of a previously unknown hominid ancestor in 1912. Though some at the time expressed skepticism about its origins and legitimacy when it was discovered, it wasn't definitively exposed as a hoax until 1953 (41 years later) when Joseph Weiner and Kenneth Oakley found evidence that the teeth had been artificially altered in shape, newer chemical testing was available to authenticate the age of the fossils, and it was discovered that they weren't even fossils, they were just old bones painted and stained to look like fossils. In the case of Piltdown Man, the people who got to determine that Piltdown Man was a hoax were... the people who discovered that Piltdown Man was a Hoax.

My question for you is: Is my reasoning circular? The person who discovers the lie is the person who makes the determination that someone else is lying... right? (Assuming, of course, that they are not in on the lie, nor had prior knowledge of the lie before it was put into effect.)

I see this rational in a very similar light to the anthropic principle where our universe must be (at least partially) suitable for life because we are here to observe it, and a universe that is wholly unsuitable for life would not have life in it to observe it. In the case of Piltdown Man, the people who made the final determination that Piltdown Man was a hoax were the ones who found definitive evidence that Piltdown Man was a hoax.

So... Am I using circular reasoning? Because it seems to me that I'm not, that the only person (or people) who could logically determine that someone is lying is the person (or people) who discover the lie. Or is it circular and all circular reasoning logically entails itself which is why it's circular?

Crap, maybe I should have taken a logic class before this one...