ABSTRACT
Latent prints are inherently invisible and thus must be developed with powders and/or chemical reagents. Fingerprint powders—both solid state and aqueous—are physical processing methods. The powder particles, applied with the appropriate fingerprint brush, adhere to the oils and moisture in the friction ridge impressions. Chemical processing requires chemical reagents that react with inorganic or organic compounds in the friction ridge impression, most commonly lipids, salts, or amino acids. It is not possible at this time to determine how long a latent print has persisted on a given surface. The accompanying laboratory exercise explores the concept that latent prints persist on various surfaces based on the type of substrate, environmental factors, and time since deposition.
