A crime scene can be read backward: footprints, their depth and spacing, abandoned objects, and disturbances in snow or ground encode the number of people present, their sex, their movements, and their emotional state. The investigator builds a narrative hypothesis from these marks and then tests each new observation against it rather than collecting facts without a theory.
A novice investigator's confidence and ingenuity can produce an elaborate, internally consistent reconstruction that is entirely wrong, because cleverness amplifies whatever premise it starts from. Experience is portrayed less as knowing more facts than as distrusting one's own first conclusions and resisting the seduction of a satisfying theory.
A person's true station leaks through behavior that disguise cannot fully suppress: the way hands are held, composure under pressure, reflexive gestures of command, and the mismatch between claimed poverty and ingrained refinement. Reading these involuntary tells lets an observer pierce a deliberately assumed lower-class persona.