Buy a cows tongue at the grocery store, slice it open length wise (top and bottom) between halves place a piece of paper that you have written the person who is lying name on, be as detailed as you can. Roll the tongue up (tip to back) and drive 7 nails, 7 pins and 7 needles through the tongue each time saying something like "(name) cannot lie."
Wrap the tongue up in red cloth and leave it in the woods with 7 pennies.