What is Luchesi's role in the short story "The Cask of Amontillado"?

Fortunato does not necessarily believe that Luchesi is an
"ignoramus." In fact, he may believe that Luchesi is at least as knowledgeable about
wines as himself. He is only telling Montresor that Luchesi is an ignoramus because that
is what he wants him to think. Throughout the story Fortunato is apprehensive that
Montresor will consult Luchesi, and Fortunato doesn't want the other man even to know
about the existence of the Amontillado.

Montresor says he
has bought one pipe (126 gallons) at a bargain price. There must still be a whole
shipload of Amontillado in the harbor. Fortunato is not anxious to sample Montresor's
wine in order to enjoy a glass or two. Amontillado is a good wine, but it is not rare;
he could easily find a bottle in a liquor store if he was so fond of it. He is not
anxious to sample it to show off his connoisseurship of wines. He is not anxious to go
to all that trouble at that time of night in order to do a favor for a friend. Fortunato
wants to make a big profit by buying as many casks of the Amontillado as he can and then
selling it in bottles. He visualizes a whole shipload containing nothing but huge oaken
casks of the finest Spanish sherry. But he has to sample it to make sure it is the real
Amontillado.

Montresor has shown he is a shrewd judge of
human character. He knows that Fortunato is already planning to tell him the wine he
supposedly bought is only an ordinary sherry and then find the ship and buy up the
entire cargo. Fortunato is rich and can become even richer. He will not only make a
profit but consider his trickery an "excellent jest." Tricks like this are among the
thousand injuries he had inflicted on Montresor over the years. Fortunato wears a
jester's costume because he thinks of himself as a jester and trickster. Montresor knows
he couldn't trust him to tell the truth about the Amontillado--if it existed. He would
taste it, wrinkle his nose, shake his head, and say it was just ordinary Spanish sherry.
Unfortunately for Fortunato, there is no Amontillado.