Blood Problems: medical ethics?

uming this is a hypothetical question, determine the source of the donated blood. Certain blood banks may pay donors for blood who need money for drugs or alcohol while the American Red Cross screens donor history and donors may have ped post-donation blood tests many times. The largest risk factor may depend upon the source. Doctors will not start a scheduled operation unless tested blood is at hand but for an emergency (gun shot wound and perhaps a rare blood type) the choice may be certain death or a second chance with possibly tainted blood. If a waiver is signed by a responsible relative or the victim that should waive any legal action against the doctor or hospital. I was once requested to donate a pint of blood at a hospital for immediate use (or standby?) and was on a donor list from previous donations (minimal risk).