Presumptive detection of blood and blood stains is one of the most prerequisite of forensic biological investigation. Most of the presumptive tests rely on the principle of redox reaction which explores the peroxidative nature of Heme found in the hemoglobin of the blood cells. Though most of such tests are highly sensitive, however, they are not specific to either blood or human blood. Many of such tests show cross-reactivity with other body-fluids that might be present in the crime scene. Similarly, plant peroxidases, metal contaminants can also lead to a false positive result. The error rate of such tests can be minimized by using suitable positive and negative controls while using these tests. Hence, though presumptive tests give us an idea of the location of blood stains or latent blood stains, their presence should be confirmed using any of the confirmatory tests.