It is possible for people to have spirits that have been assigned to them by the devil. The evidence for this is in people whose life rapidly starts to disintegrate. People who may have been in church regularly are now out for 6-7 weeks at a time. They no longer serve God, and no longer have the flow of God. They have been assassinated by the devil!
In Breaking The Assignment of Spiritual Assassins, Michael Pitts rolls out the case for this, and the remedy for yourself, and for those in your circles, to be fully revived.