Clary Fairchild: How did you know I had Shadowhunter blood? Was there some way you could tell?

Jace Herondale: I guessed… It seemed like the most likely explanation.

Clary Fairchild: You guessed? You must have been pretty sure, considering you could have killed me.

Jace Herondale: I was ninety percent sure.

Clary Fairchild: I see… (Clary slaps him)

Jace Herondale: What the hell was that for?

Clary Fairchild: The other ten percent.

From the book The Mortal Instruments: City of Bones (Book One) | Written by Cassandra Clare