Target player sacrifices a creature and loses 1 life.
"Everyone should owe you something." —Geth, Lord of the Vault
Official Rulings for Geth's Verdict
6/1/2011 : As long as the player is a legal target when Geth's Verdict resolves, that player loses 1 life even if he or she didn't sacrifice a creature (most likely because he or she didn't control any).