How can invisible fingerprints, made up of only sweat, be seen?
The term ‘latent’ means invisible. Technically, prints which are visible, for instance a bloody fingerprint impression, are referred to as ‘patent’ prints. Latent impressions, made up only of sweat and/or oil, are very difficult to see. Through the use of crime scene lighting techniques, photography, and the application of chemicals, these impressions are enhanced so that the details of the print can be viewed. Chemicals used range from the standard black powder to specialized chemicals which react with amino acids in sweat, are specific to the sticky side of tape, or are fluorescent when exposed to particular wavelengths of light.
