Reflection begins with a problematic difference between a system of thought already in the mind, and some fragment that one wants to include in that system.
A detective reflects on someone's death because there's a conflict between the fact of the person's death and something already in the mind. Detectives order their experience on the principle that events have causes.
This event challenges inclusion in that system of thought. The detective makes the event fit by learning, observing, and reflecting on the details of the problem. Observation is guided by what experience has already taught such as which details are likely to be relevant.
Consequently, the detective pays more attention to bruises apparently made by some blunt instrument, for example. The details don't come from focusing on one thing, one piece of evidence, or one fact. The basis of a new thought must be broad. If the question was merely who might have used the blunt instrument, their would be an indefinitely large number of answers. The question is who must have done this in view of unemptied pockets, signs of a struggle, the butler's loyalty, and perhaps a hundred other things---all relevant details.
A successful conclusion from a single factor alone would be an accident. The conclusion come from all of the facts and rules of thought taken together. The problem is to fit a detached fact into the entire overall system.