Is there a pagan spell to make someone tell the truth?

A spell is not just the Wording. You have to develop the base skills to do an effective spell. If you want someone to tell the truth, look in to their eyes. Focus your eyes few inches bhind their eyes. Make them look at your eyes. Stand or sit streight and expect the truth from them. There are methods to fascinate a person just by looking at them. At one point they become unable to lie, and will tell you the truth! These things comes under Hypnotism and Magnetism, not spellcraft...