Forensic fingerprinting

Forensic fingerprinting is the process of detecting and analyzing the unique ridge patterns left by fingers on different surfaces, often used in criminal investigations because no two individuals share the same prints. These impressions can be visible, impressed, or latent (invisible), and several methods are used to develop them, including powders, chemicals like ninhydrin or silver nitrate, and iodine fuming. Iodine, in particular, is useful because its vapors interact with the oils and fats left behind in latent fingerprints, producing a temporary brownish image. When tincture of iodine is combined with citric acid and hydrogen peroxide, the reaction can enhance or stabilize the visualization: citric acid acidifies the solution while hydrogen peroxide oxidizes iodine, sometimes intensifying the color or prolonging the fingerprint’s visibility. While this iodine–citric acid–H₂O₂ method is not a standard forensic technique, it serves as a powerful demonstration of how chemistry can be applied to reveal hidden prints in educational or experimental settings.