.... witnesses were usually right when they said that something had happened at a particular place, although they could be wildly wrong about what had happened. (R.V. Jones - The natural philosophy of flying saucers)

The biggest concern with UFOs and eyewitness testimony has to be how witnesses perceive what they saw as compared to what they actually saw.  Many UFOlogists have difficulty in recognizing the fact that eyewitnesses are not perfect mechanisms for recording events.  As a result, many UFO stories are considered unexplainable by UFOlogy. The following articles discuss some of the problems with eyewitness perception.