Iniquitous Auditor

Whenever you cast Iniquitous Auditor, choose an opponent. During that opponent's turn, anytime he or she would draw a card, cast a spell, tap a card, or end his or her turn; count the number of cards in his or her hand and under his or her control. Make note of this total.
During your upkeep, if any noted total from the chosen opponent's previous turn was more than 10, he or she loses 3 life.