This lab will demonstrate the very simple Kastle-Meyer test to determine the presence of hemoglobin expected in blood.
"Out, Damn'd Spot! Out I Say."
So sayeth Lady Macbeth in true Shakespearean fashion in Macbeth (Act 5).
But how did she know the spot was blood...unless she put it there!?
At a crime scene we expect to see blood stains and we're certain that the dark brown spots are indeed blood. but, we dare not say so, until we have completed a presumptive field test. With the ever presence of cell phone video recording, a simple comment ("did you swab those blood stains") can be argued in court that the technicians were not unbiased in their task performance.
We have a simple, inexpensive field test that will confirm that a stain or spot is blood- although not necessarily human blood. That analysis is best completed as a confirmatory test in the lab.