This presumptive blood test is designed to be a simple, one shot test for the presence of blood. This portable test will fit in your pocket and allows you to test suspect stains without taking the time to mix chemicals. Simply place a small quantity of the stained material, or a portion of a swabbing of the stain, into the kit and crush the color-coded vials in sequence. Their formulation has long been accepted by the courts and proven in the field. This kit will automatically let you know if it has expired, thus minimizing the chance of a negative reading.