Download Analysis of Blood: Human vs

Lab Analysis of Blood: Human vs. Animal Blood
In the case of poor Moley Mole, there was a lot of blood found at the scene.
 Do you believe that all of that blood came from Moley?

Were there signs of a struggle? What were they?

Is it possible that Moley put up a fight for his life and injured the perpetrator?

What signs at the scene indicate that some of the blood may have come from the
perpetrator?
After an investigator has determined that a stain is blood, the next step is to learn whether it is
human or animal blood. The precipitin test (test that distinguishes between human and animal
blood), the standard method, uses an animal serum (a liquid that separates from clotted blood)
that contains antibodies (proteins in the blood or secretory fluids that tag, destroy, or neutralize
bacteria, viruses, or other harmful toxins, producing an immune response) specific to human
antigens (foreign substances in the body that are capable of causing disease. The presence of
antigens triggers an immune response, usually the production of antibodies.); therefore, it reacts
to agglutinate (a type of allergic reaction where red blood cells clump together, usually in
response to a particular antibody) human blood. The test is so sensitive that the blood can be
greatly diluted. Also, bloodstains many years old can test positive.
In order to analyze the blood evidence that you collected at the scene you will need the
following materials.
Small test tube
Crime scene blood evidence
Known human blood
Human antiserum
Known animal blood
Beral pipets
First you will need to observe the reaction of known samples of human and animal blood with the human
antiserum.
1. Add about 1 ml of human antiserum to a small test tube
2. Carefully pour 1 ml of known human blood into the same test tube down the sides of the test tube
without disturbing the bottom layer.
3. Because the blood is human, there will be agglutination where the two liquids meet. Be patient;
sometimes it takes a while. Record your observations.
4. Repeat steps 1 – 2 with the known animal blood. Record your observations.
5. Now repeat steps 1 – 2 with the samples of blood taken from the scene of the crime.
6. Record your observations and determine which samples are human and which are animal. Make
this notation on your crime scene sketch.
7. The contents of all tests can be poured down the drain.
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