What is guaiacum test – in forensic science

A presumptive test for blood, one of the first developed but no longer used. It relied on guaiacum (a resin isolated from trees) in combination with hydrogen peroxide. If a stain turned blue when treated with these reagents, it was considered a positive result indicative of blood. However, as with all presumptive tests, the results are not conclusive, nor do they prove that the blood is human.