In the quotes below, Holmes is actually talking about a different sort of tangent. He was trying to explain that when you examine the evidence you need to be careful to not follow a false lead. Sometimes you find pieces of evidence that just aren't relevant to your case (same/similar name, wrong person). It is important to evaluate all of the evidence and decide what is relevant and what isn't. You don't want a false lead taking you down the wrong investigative path. It is very important to document WHY a certain piece of evidence was found to be not relevant. People that read your research need to see that you evaluated everything that you found.
"It is of the highest importance in the art of detection to be able to recognize, out of a number of facts, which are incidental and which are vital. Otherwise you energy and attention must be dissipated instead of concentrated.” [Holmes to Watson, "The Reigate Squire"]
"Having gathered these facts, Watson, I smoked several pipes over them, trying to separate those which were crucial from others that were merely incidental.” [Holmes to Watson, "The Crooked Man"]
“The principal difficulty in your case lay in the fact of there being too much evidence. When was vital was overlaid and hidden by was irrelevant. Of all the facts which were presented to us, we had to pick just those which we deemed to be essential, and then piece them together in their order, so as to reconstruct this very remarkable chain of events.” [Holmes to client Percy Phelps, "The Naval Treaty"]
Copyright © 2012 Michele Simmons Lewis