A crime scene can be read backward to the sequence of actions that produced it: the position of objects, the state of a meal, footprints and the angle of a wound each constrain what could have happened. By insisting each observed detail be explained by a single coherent story, the investigator narrows many possible pasts down to one.
A chain of inference that fits every available clue can still point at an innocent person, because the clues were themselves arranged or coincidental. The more elegant and complete the deduction feels, the more its author resists the doubt that would correct it, so brilliance in reasoning becomes a source of injustice rather than a safeguard against it.
Social position and selfhood can rest entirely on a record that someone else controls, so a swapped or falsified origin silently assigns one man's name, fortune and future to another. The substitution holds until a single witness to the original act is removed or exposed, which is why that witness becomes both the keystone and the target.