You are right; I am not a clinical psychologist. In some cases, I deal with people when the shit has hit the fan. That is, I know how most people react to really bad events because I see it quite regularly.
In other cases, I deal with the long, slow, and painful descent age and terminal disease bring to people's mental faculties.
In yet other cases, I get to talk with regular 911 callers that we wake up with Narcan, drunks that are simply sleeping on the side of the road, drug seekers that have "fallen" or been "hit by a car" (with no injury to speak of)... and more.
So, generally speaking, I get to see people when they are being quite "real" or at least "true" to the event that has taken place. That doesn't make me an expert in human psychology, and I would not claim such. However, as a group, EMS personnel can cut through the bullshit a lot faster than most. Over the course of years, comparing what people say to what they do... one can not mistake the patterns. No "human psychology" textbook will teach you that.