What are the prefect's strengths and weaknesses as a detective in "The Purloined Letter"?

You have asked a question about one of the earliest
detective stories, upon which Sir Arthur Conan Doyle based his famous detective Sherlock
Holmes. One of the key ingredients in this genre is the bumbling, well-meaning
policeman, who is dismissive of the skills of private detectives such as Dupin in this
story, and is determined that good old-fashioned police-work will figure out the crime.
You would do well to think about how Poe builds this picture up in this short
story.

It is clear that Poe is none to complimentary
regarding Monsieur G. of the French Police. From the start there are somewhat dismissive
remarks made about his limitations. For example, consider how the narrator comments upon
Monsieur G's comment of Dupin's that he finds it easier to reflect in
darkness:

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"That is another of your odd notions,"
said the Prefect, who had a fashion of calling every thing "odd" that was beyond his
comprehension, and thus lived amid an absolute legion of
"oddities."

The inference is
clear - there are lots of things that are "beyond his comprehension", and because he
lives amidst a "legion of oddities" his ability to comprehend is obviously not that
impressive or powerful.

However, it is clear that Monsieur
G. does have his strengths. As Dupin begins to reveal how he gained the letter to his
friend, he does say:

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"The Parisian police... are exceedingly able in
their way. They are persevering, ingenious, cunning and thoroughly versed in the
knowledge which their duties seem chiefly to demand. Thus when G. detailed to us his
method of searching the premises at the Hotel D., I felt entire confidence in his having
made a satisfactory investigation - so far as his labours
extended."

Dupin continues to
support this by saying all the extensive measures that Monsieur G. took were "carried
out to perfection" and that if the letter had been placed where they were looking they
would have found it. However, Monsieur G.'s greatest failing in this case was his
inability to think outside the box and consider other alternatives. This is what led to
his failure to recover the letter - his lack of perception and
comprehension.

So, whilst Monsieur G. is a diligent,
hard-working Prefect who is good at his job, he lacks a crucial element of imagination
and wider perspective that separates him from the greatness of Dupin. It is this fact
that is recognised and exploited by the politician who has purloined the letter, and, in
turn, it is Dupin's ability to do precisely what Monsieur G. is unable to do that allows
him to solve this curious case.