by TurncoatScopolamine Suicide.
Just blow it at their face in powder form and give them suicidal instructions. Don't even need to leave any fingerprints.
Edit: Just learned about White Snakeroot. Pretty interesting, seeing as the root itself has medical purposes when turned into a tea or poultice.
http://topdocumentaryfilms.com/worlds-scariest-drug/
This stuff is amazing, i want a big bag of this if i can get my hands on it at some point in my life.