it's a test used in criminology for determining the human or other source of a bloodstain.
The precipitin test identifies whether or not blood found on a crime scene is human or another species. Knowing the origin of the blood helps the forensic lab determine whose blood it is. The precipitin test can be preformed directly at the crime scene, this way you do not have to send false samples to the laboratory.
The precipitin test measures the response from the immune system of another animal by making anti-human antibodies to protect from human blood proteins.
