Blood Identification

A few drops of a red substance are found at the house of a missing person. Are the drops red paint, ketchup from a hot dog, or possibly blood? The identification of the substance is important and will help a detective know which way to direct an investigation. Try the following activity to see one way that investigators determine the identity of a red substance.

Materials
- eyedropper
- red watercolor paint
- ketchup
- blood (from the bottom tray of a meat container)
- plate
- tap water
- Hemastix (available from many drugstores)

Caution: Be sure to wash your hands thoroughly after handling raw meat.

Procedure
1. Use the eyedropper to place 1 drop of red watercolor paint, 1 drop of ketchup, and 1 drop of blood on the plate.
2. Add a drop of water to ech red drop to make sure that they do not dry out.
3. Put a Hemastix strip in each solution. What happens? What color does the Hemastix strip turn in each solution? What color indicates blood?

Explanation

The Hemastix change color in blood. A Hemastix strip contains chemicals that will react with the chemicals normally found in blood. This simple test is often done at the scene of a crime as a quick way to determine whether a substance is blood. Later, Samples are tested in the laboratory to confirm the field test. Other tests, such as bloodtyping or DNA profiling, give more detailed information about the blood and the individual it came from