Lifting and Developing Prints

Depending on the surface from which a fingerprint is being lifted, two different procedures may be utilized. On a nonabsorbent or hard surface, examiners use a powder to lift prints. In contrast, on a soft or porous surface, certain chemicals may be used to collect fingerprint evidence.

    Nonabsorbent/Hard Surfaces (wood, tile, glass)

 The color of the powder used at a crime scene depends on the surface from which the print is being lifted. If the surface is of a light color, a black powder will be brushed over the print. If the surface is darker, a light powder will be used. The powder is brushed over the fingerprint carefully so as not to disturb any of the identifiable ridges. Tape is then applied over the print and then reapplied onto a sheet of paper to be analyzed in a lab.

Soft/Porous Surfaces (cloth)

Iodine Fuming- The material from which a print is to be extracted must be placed in an enclosed chamber with iodine crystals. The crystals are heated, forming a vapor which makes the print visible. However, the print will only be visible while the reaction is taking place, so a picture must be taken for examination or the print must be preserved with sprayed 1% solution of starch in water.

Silver nitrate- A powder form of silver nitrate (AgNO₃) must be brushed on the print and exposed to ultraviolet light to make the latent print visible with a very distinguishable color.