Death Doubt

Death Doubt / 死神ダウト is a lying card game in which two players push the Grim Reaper onto one another, trying to wear down their lifespan! If you think your opponent is lying, you doubt them. You can doubt as many cards as you like, but the more you doubt, the more negative points you will have. Which of the following will help you spot the other person's lies: probability, expression, or strategy?