Abstract
There are several presumptive, or screening, tests for blood available. The benzidine, tetramethylbenzidine, o-tolidine, Phenolphthalein, leucomalachite green, and luminol presumptive tests for blood are classified as catalytic tests. These tests are based upon the peroxidase-like activity of hemoglobin and its derivatives. Proper safety and health precautions should be taken if o -tolidine is used as a reagent in the screening test for blood. With the use of a spraying device, luminol reagent is applied on objects or areas containing traces of suspected bloodstains. The luminol test is nondestructive and does not interfere with confirmatory or subsequent serological tests of the blood. Screening tests for blood are so sensitive that a negative test can readily be interpreted as proof that no blood is present within detectable limits. Substances other than blood may contain oxidants which can cause a positive reaction with the presumptive tests for blood in current usage.
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