This post is quite old, but I ran across it because I am trying to research just what an "I don't know" answer establishes as a fact. Seems to me it only establishes that the witness has no personal knowledge to answer. To a Q: Was the traffic light green?, the answer "I don't know" does not establish that it was green. Is "it could have been green" a reasonable inference from that answer? Maybe, I suppose, as there are limits to the colors (red, green, yellow only, so it could have been any of those). How about this: Q We talked about the distance she was from you at the time you first saw her. How far away from you do you think she was when you first applied your brakes? A I don't know. Q Was it more than 10 feet? A I'm horrible at judging distance. All I know it happened instantly. In my mind it was instantly. Q So you don't know if it was more than 10 feet? Counsel: Objection. Asked and answered. Answer if you can. A I don't know. In this exchange, is the witness' answer "I don't know" evidence that she could have been 10 feet away when she first applied her brakes? I know this stuff hardly ever comes up, and I cannot find anything anywhere.