Once Kurapica manages that, you have two choices: use nen and have your heart pierced (lol ded?) or don't use nen and lose anyway.
Also, if I'm not mistaken, Chain Jail allows Kurapica to interrogate his victims. Risky on his behalf, because if they aren't Ryodan meat, he instantly dies. If they ARE Ryodan, they aren't offered the choice to lie when answering to him. If they do that, THEY die instead.