Honesty comes from within. As you said, once a dishonest will always be in his character, so giving another chance to a dishonest employee is really wasting of the chance. But if someone have done anything wrong unintentionally, then one chance could be given.I am not of the opinion that you will need to warn your dishonest staff first from their dishonest ways because as far as I am concerned for anyone to be honest means that that is part of their character and so it will be very difficult for them to change so as for me I will suck start an employee without thinking twice