Evidence is preferably forwarded by registered mail or railway express, as these means provide records of dispatch and receipt.
Elimination or suspect fingerprints are best enclosed with the evidence itself, with a notation as to the type of prints forwarded.
CHAPTER XIII
Powdering and Lifting Latent Impressions
The sole purpose in "developing" a latent impression is to make it visible so that it may be preserved and compared. Various powders and chemicals are used for this purpose. When a latent print is plainly visible, it should be photographed before any effort is made to develop it.
No attempt should be made to brush or apply powder to prints in dust, obviously greasy prints, or bloody prints, as this will almost surely destroy them. Objects which have been wet or immersed in water may still bear identifiable latent impressions. Before any examination is attempted, however, the object must be dried.
Powder brushed lightly over a latent-bearing surface will cling to grease or moisture in the ridges of a latent print, making it visible against the background. Obviously, a powder should be used which will contrast with the color of the surface. Photographic contrasts should also be considered.
A gray powder and a black powder are adequate for latent print work. Many fingerprint powders of various colors and compositions are available from fingerprint supply houses but none are superior to the gray and black.