Transcribing Personality To Paper

Not sure if this is the right place for this, so if not please let me know.

My chemistry professor is kinda a strange guy. After most things he says, especially things not said in chemical formula, he gives this very particular laugh. It's very non-sleazy used car salesman (yes, it's possible) with a touch of sociopath-trying-to-play-human. Come to think of it, he does kind of remind me of Dexter...

Anyways, I'm trying to find a way to have a character give off this same mannerism, and I was wondering if anyone has done something like this before and has advice on how to do it? I've been thinking maybe using other characters to describe the mannerism, but I feel like there should be something through narration as well. Advice?

what's your POV? who's your narrator ?

Good questions. As of yet, there isn't an answer for either. The chem teacher isn't slotted to go into anything specific just yet, just looking to add that character description into my writer's toolkit so to speak. I should have put that in my original post.

At a guess, I would use the character in one (or more really, I could use more reoccurring characters that aren't main characters) of my supernatural investigative stories. I'm bad with technical terms, but as it stands the stories are third person with nothing special about the narrator. POV is primarily one of five or so main characters, depending on the scene. I've got a few ideas here and there about how the different characters would react to the quirk, but what I'm brainstorming on is how to present the character beyond just what the POV character is thinking.