To find out whether the stain is human or not the following test is done
High-Yield Explanation
Precipitin test This is a precipitation reaction by antigen and antibody. Human blood is injected into a rabbit every third day for 3-5 times. After this the animal is kiledk and the antiserum is collected. This is used for precipitin test to find out a paicular tissue or stain is human or not. Ref: FORENSIC MEDICINE AND TOXICOLOGY Dr PC IGNATIUS THIRD EDITION PAGE 318