and then there is common sense and street smarts
My son is a police officer, a patrolman and he said he learns a lot just watching people he comes into contact with and listening to what they say rather than talking all the time to them. He will ask a question and then watch and listen to their reactions, their body language and he has learned to figure out who’s BS’ing and who’s telling the truth or just nervous.
He said there is one officer on their department who honestly believes anything he is told. Says you could hold him up through the mail.