Before you go in front of a jury, it's important that you're prepared. The way you look and act can make as much of an impression as the testimonies of those who want to see you prosecuted. The way you are perceived can make you look more or less truthful than you are.
Your attorney should take time to make sure you're ready to present yourself in a way that makes you optimally persuasive and easy to like. No jury wants to convict someone it generally likes.