1) Consider their personality and behavior. Those who tend toward abuse often behave in certain ways. They may often blame other people, including you, hold grudges, feel entitled to special treatment for no reason, express superiority over peers, take your small comments or mistakes seriously, express jealousy, and fluctuate between these negative actions and excited ones. Take note of these moments in your conversation, whether in person or over the phone/email. Learn more about abusive tendencies.
2) Look for momentary and spontaneous signs. It’s likely that you will not have too much opportunity to converse or understand where they are coming from. You can look for signs of anger, which often leads to violence.
Think about the fight-or-flight response. What prepares someone to fight? They may change how they breathe, ‘beef up’ or increase the size of their chest, clench their fists, twitch their facial muscles, flex their neck muscles, clench their jaw, and even lose control over the fluency of their voice.
Other behavioral signs include raised voice, increased sarcasm, rough actions, and faking loss of interest. Learn more here.
Other facial signs include lowered eyebrows, narrowed eyes, wrinkled forehead, tensed eyelids and tensed lips. Learn more here.
3) Consider their history, if you can. It is true that the best predictor of future behavior is often past behavior. Does this client have a) excessive alcohol intake, b) a history of violence or criminal activity, c) or a history of childhood abuse? Research simply shows that these have high correlation with violent actions, so maintain a relaxed and non-contentious environment. This does not guarantee that one will cause the other. Consider how they may have resolved problems in the past– do they believe that using force is sometimes a good method? Learn more about research here.
It is best to keep a relaxed environment and help the client feel that he is getting what he desires. However, if it seems that he will be physically violence, or wants to fight for what he wants (rather than just get it), it is best to leave the situation. If possible, spot suspicious email or phone behavior and do not see that client.