Defective Detective can't be blocked.
When Defective Detective enters the battlefield, a person outside the game looks at target opponent's hand and chooses a card from it. That player reveals that card.
1/19/2018 You can choose any player not currently in your game. This includes people who used to be in your game but left it.
1/19/2018 It doesn’t have to be someone who plays Magic. This may be fun.
1/19/2018 If there’s no one around to make a decision, you can call or text someone if you need to. If there’s a physical action required, such as high-fiving, you’ll need someone there.