Sociopath, psychopath or just plain old BS artist, easiest way to catch them is play stupid.
They all believe they are smarter than you and can outsmart you.
Sucker them in with the stupid act and probe their knowledge with “stupid” questions.
Most also have a “tell”.
One “tell” that is common is they start whispering even though you’re in private and no one else can hear them.
The definitive study of the sociopathic persona is “The mask of sanity” written by Hervey Cleckley. It was first written in the 1940’s and never been out of print but has gone through several revisions.