Experts are seldom wrong in a random way - that is the province of outsiders, cranks, and the half-informed. The expert has at his disposal a wealth of actual data: research, personal experience, or theories devised by those similar to himself, which he has had some opportunity to observe in the actual. He does not guess that things are linked together because some intuition tells him that it should be so. He has seen them linked a dozen or a thousand times, in the numbers, in the lab, or on the street.
No, when the expert is wrong it is often at a perfect 180 degrees from the truth, exactly backward, reversing cause and effect or examining only one side of the balance scales. In fact, this is what we should always fear most from the expert, that he is wrong in the most invisible way, on the correct path but headed in the wrong direction.