Oil Red O (ORO) reagent for detection of latent fingermarks: a review

Fingerprints are most frequently used to establish the identity of a person in medicolegal cases. Wide range of methods (optical, physical, and chemical) can be used to detect latent fingerprints on porous and non-porous items recovered from crime scenes. Oil Red O, also called solvent red 27, is a lipophilic dye, which means that it stains fat and lipid components in biological samples. It is also used to stain oil and waxes to a red hue. Oil Red O is used to detect latent fingerprints on dry and wet porous items like paper and cardboard. The reagent develops clear, stable, and red-colored fingerprints which may be discerned in natural light. Although the physical developer can also lift latent impressions from wet porous surfaces, the method is a multistep one and requires immersion of delicate, paper-like articles in a sequence of working solutions. Compared to that, the operational steps of Oil Red O method are simple and cost effective and require less equipment to process items.