Can forensics gather blood on one pretense and use it against you on another?

If forensics gets permission from a suspect to test blood for a bacterial infection or something similar, can that blood legally be tested against DNA that was found at a crime scene and hold up in a court of law?
Yep. Once they have it, they can pretty much do what they want with it.
yes they can and once you give it it belongs to them. so, i wouldnt be agreeing to anyone having my blood for any reason. and guess what? if you keep your nose clean you will never have to be wondering about stuff like this.
I GUESS IT'S POSSIBLE EVEN THOUGH IT DOESN'T SOUND ETHICAL. IT MAY OR MAY NOT HOLD UP IN COURT BECAUSE OF THE WAY THEY GOT IT. BUT ONCE THE THOUGHT HAS BEEN PUT THERE IN THE MINDS OF OTHERS IT'S A BIT LATE. PRAY IT'S NOT THE SAME BLOOD TYPE!
Yes they can. Why do you ask? O.o


Answers:
Yes they can. Your D.N.A. is put in the computer just like your finger prints.