Witness
From Conservapedia
For the movie, see Witness (film).
A witness is one who sees, knows, or vouches for something[1]; one who testifies as to what he has seen, heard, or otherwise observed; "a person called upon to observe a transaction, signing, etc. in order to testify concerning it if it is later held in question"[2].
"Every witness is an editor: he tells you not everything he saw and heard, for that would be impossible, but what he saw and heard and found significant, and what he finds significant depends on his preconceptions."[3]