Joe Navarro is an American author, public speaker and former Federal Bureau of Investigation agent and supervisor. Navarro specializes in the area of nonverbal communication or body language and has authored numerous books including, What Every Body is Saying and Louder than Words.
In American culture an averted gaze and eye avoidance are perceived as guilt: 'I've been naughty. I'm ashamed. I've been up to no good.' It's very powerful and you have to factor it in as part of your message.