When a person is bound or oppressed, he does things that are beyond human reasoning and plays the fool beyond his or her control. Notice, I did not say possessed. This is because a Christian cannot be possessed--he or she can only be demonized or oppressed. For a Christian to be possessed, he or she ceases to be a Christian, because the demonic forces have completely taken over his or her spirit being. This has to occur willingly. Only an unbeliever whose spirit is defenseless and open to occupation can be possessed.
It is important to know the patterns of behavior that provide you with the evidence of demonic oppression. There are stages through which satanic oppressions or possessions manifest. When you begin to observe the signs, it will help you identify what is going on.