The Criminologist (An Expert) is a character in The Rocky Horror Picture Show. He is played by Charles Gray.
The character is based on The Narrator from the The Rocky Horror Show (who in turn was based on British broadcaster and crime writer Edgar Lustgarten). The role was originated by Jonathan Adams in the Original London Cast production. In The Rocky Horror Picture Show: Let's Do the Time Warp Again, the character is called "The Narrator / Criminologist", and is portrayed by Tim Curry