<P> Placing the hand of a dead or unconscious person on a scanner to gain unauthorized access has become a common plot device . However, a MythBusters episode revealed that this doesn't work (at least with the scanners available to the program). But Adam Savage and Jamie Hyneman found a way to convert fingerprints lifted from the hand to a photographic form that the sensor would accept . For obvious reasons, they refuse to reveal the technique . </P> <P> In the 1930s criminal investigators in the United States first discovered the existence of latent fingerprints on the surfaces of fabrics, most notably on the insides of gloves discarded by perpetrators . </P> <P> Since the late nineteenth century, fingerprint identification methods have been used by police agencies around the world to identify suspected criminals as well as the victims of crime . The basis of the traditional fingerprinting technique is simple . The skin on the palmar surface of the hands and feet forms ridges, so - called papillary ridges, in patterns that are unique to each individual and which do not change over time . Even identical twins (who share their DNA) do not have identical fingerprints . The best way to render latent fingerprints visible, so that they can be photographed, can be complex and may depend, for example, on the type of surfaces on which they have been left . It is generally necessary to use a' developer', usually a powder or chemical reagent, to produce a high degree of visual contrast between the ridge patterns and the surface on which a fingerprint has been deposited . </P> <P> Developing agents depend on the presence of organic materials or inorganic salts for their effectiveness, although the water deposited may also take a key role . Fingerprints are typically formed from the aqueous - based secretions of the eccrine glands of the fingers and palms with additional material from sebaceous glands primarily from the forehead . This latter contamination results from the common human behaviors of touching the face and hair . The resulting latent fingerprints consist usually of a substantial proportion of water with small traces of amino acids and chlorides mixed with a fatty, sebaceous component which contains a number of fatty acids and triglycerides . Detection of a small proportion of reactive organic substances such as urea and amino acids is far from easy . </P>

The first use of fingerprints in the united states was by the