Final answer:
Dupin's analytical process involves matching facial expressions to thoughts or sentiments, but its reliability is subjective and not universally accepted.
Step-by-step explanation:
Dupin's analytical process, as explained in the text, involves observing facial expressions and matching them to corresponding thoughts or sentiments. While this may seem like an unconventional approach, it can yield reliable conclusions depending on the accuracy of the observer's interpretation. However, it is important to note that this method is not widely accepted as a scientific or foolproof means of deducing someone's inner thoughts or character traits.