In The Dark Knight Rises, at the beginning of the film Bane kidnapped a guy from the plane, then he draw thedrew blood from the guy he kidnapped. And then throughout the movie I didn't see any news regarding this kidnap scene. But, before the end of the movie I'm getting to knowwe find out that, the guy kidnapped by Bane was Dr Pavel,. Bane needed him to convert the fusion project into a nuclear bomb and Dr Pavel was the only guy who could have done it.
But iI don't understand, why did he draw blood from Dr Pavel?