From SA Mafia Wiki
A Flavor Cop is a Cop that receives information about a player's flavor instead of their alignment or role. This information can vary based on the role, theme of the game, and moderator discretion. One example of Flavor Cop is a Gunsmith, which determines whether a player has a gun or not. He then uses this information to help decide if that player is town or scum as both alignments can return a positive or negative result depending. Another example of this is in Harry Potter and the Circus of Chaos run by Token Female and Chellesandcheese, where the flavor cop was able to find out what Hogwarts House to which a player belonged. This was used to help determine whether a player was town, scum or third party, as the scum had fakeclaims contradicting their "real" Houses.
Note that a flavor cop shouldn't use his results to peg a player as town or scum on the results alone, it should be used to help verify claims from players and as information to be weighed in addition to game play.