Old technique (iodine fuming) plus new technology (digital subtraction) equals more options for the development and enhancement of latent fingerprints.
The use of iodine fumes to locate latent fingerprints has been available to criminalists for years. Iodine fumes react with sebaceous materials in a fingerprint in a reversible physical process that does not alter or interfere with the subsequent application of other development techniques such as 1,2 Indanedione, Ninhy-drin, DFO, etc.
The visible image of the fingerprint, which arises subsequent to the application of iodine vapors is a transient image that will fade over time. Therefore, the image must be photographed as soon as possible after it is visualized. Some may consider the disappearance of the iodine vapor image to be a disadvantage or, at the very least, a nuisance and opt to utilize other, more stable methods for developing latent fingerprints on surfaces such as paper, wood, glass, and plastics.
With the advent of Adobe Photoshop, the use of the “older” fuming techniques of iodine vapors when combined with the “newer” Photoshop techniques of digital subtraction can offer another effective tool to develop and enhance latent images on visually difficult or distracting backgrounds. This method offers an easy, cost-effective mechanism for developing and visualizing images on difficult backgrounds, while at the same time maintaining the integrity of the fingerprint for subsequent application of other processing chemicals/techniques.