Person A went into a site such as "Chatroulette" and typed in "sext" as interest. This matches people up to different people of the same interest at random. Person A, a 17 year old male, came across Person B, a 17 year old female. A asks for her IM username, and B readily gives it.
Now in the IM chat box, B is the one initiating the conversation. B asks, send me a pic of your d***, and A says, no - I have no camera. B then says, oh but let's sext anyway. A sends obscene messages - but none indicate any further action towards B. They're just "theoretical", or "story-like" sexual statements-- Like an erotic novel. After a while, A asks B to complete the story, but B vaguely answers. A says, I'm bored, and leaves.
Illegal? Does it change the case if B was an undercover cop?