The Bulgarian defector Georgi Markov was killed by a pellet of ricin in the thigh... Almost the same week, another Bulgarian defector, Vladimir Kostov, was in similar way attacked in Paris. He survived (and lives now in Bulgaria) after being very seriously ill for rather long time.
I mean, it gives some hope, isn't it?
Not if they decide to make it an aerosol powder. Ricin paralyzes the respiratory system when inhaled. You end up suffocating and drowning.
Ricin is made from castor beans, rather easily.