Forensics Daily #6: Detecting Blood Stains

Q: If CSI found a possible murder weapon on scene, spotted some red stains on it, and wondered if that was actually blood, what and how to do?
A: CSI would carry out a test called “Kastle-Meyer test”. This test consists of spraying two chemicals to the stain and observe the chemical reaction to it. The two chemicals are Phenolphthalein and Hydrogen peroxide. In general, if there is blood, the swap would fade to pink instantly. The instant change was because the chemicals react with each other under the presence of blood. The instant change was because of the haemoglobin in the blood acted as a catalyst.