First, the look is suspicious.
(1) when you answer questions, your eyes are flickering and panicky.
(2) when talking, the interrogation object suddenly hesitant, answering the contradiction, or suddenly stop answering.
(3) to see the security guard take the initiative to speak in front of him, with too much enthusiasm and no specific details.
(4) see the security guard immediately evade, or be asked by security guard, leave immediately.
Second, behavior is suspicious.
(1) the contradiction between behavior and identity. People who pretend to be different occupations or identities tend to show off in dressing, speaking, language habits, professional habits, and human behavior.
(2) the contradiction between behavior and time. It does not follow the normal rules of time.
(3) the contradiction between the behavior and the environment. Incompatible with the surrounding environment, such as running panic, sneaky, hiding away.
Third, the features of the body are suspicious. Physical features are similar to those required by public security organs.
Fourth, the relationship is suspicious. When two people walk together or many people go together, they can not tell the basic conditions of their age, name and so on.
Fifth, dialects are dubious.