How do forensic investigators test for the presence of blood?
Investigators often find blood stains during their examination of a crime scene. They also find stains that could either be blood or some other similar looking substance like reddish-brown paint or tomato sauce. In this lab,students will employ two chemical tests that forensic scientists use to signify the presence of blood.
Since these work due to chemical reactions, they produce false positives and therefore are presumptive tests, not conclusive for blood.
After performing the presumptive tests, the students test two stains from a crime scene that might be blood.