Digital Fluorescence Photography System and Reagents for Latent Fingerprint Visualization & Recording

A developed and identified image on material from a crime scene is perhaps the most powerful evidence linking a suspect to the scene. Among the types of useful images, fingerprints have long been considered one of the most valuable types of physical evidence that can be found at a crime scene.

Fingerprints can be generally classified into three types: visible, impression and latent. Of these, visible fingerprints can be photographed directly, and impression fingerprints can usually be photographed under special lightning conditions. Latent fingerprints, however, are more difficult to record since they first must be made visible.

There are three general groups of techniques for making latent fingerprints visible: physical, chemical and instrumental techniques. To understand the applicability and limitation of these various approaches it is necessary to consider the chemical composition of fingerprint residues. Latent fingerprints are composed of a variety of chemicals exuded through the pores in the fingertips. The primary component is ordinary perspiration, which consists mostly of water and evaporates after a short period of time. Other inorganic, organic and biochemical compounds can remain on the surface for extended periods of time. Some of these are water soluble such as amino acids, peptides, salts, glucose, lactic acid, ammonia, riboflavin, and others are water insoluble such as oils and other sebaceous secretions (lipids).

A number of satisfactory methods are in wide use for visualization of the water-soluble portion of latent images, including the cyanoacrylate fuming method, and fluorogenic visualization with amino-acid reactive reagents. However, an inherent shortcoming of this approach is that amino acid solubility often results in loss of latent image detail, or worse, in complete image loss in samples that have been exposed to water or polar solvents.

In contrast, latent lipid images are much more robust and durable because of their water insolubility. Furthermore, lipids are more abundant, and persons leaving indications do not always leave amino acid images but may leave lipid images. Yet, current methods for latent lipid image visualization, such as powders, physical developer, and aqueous colloidal gold deposition, have limited applicability, low sensitivity and work well only with fresh fingerprints.

Ciencia has developed proprietary fluorescent reagents that are highly effective for visualization of latent lipid fingerprint images. These reagents directly label the lipid components of fingerprints with high sensitivity and extremely low background fluorescence. Moreover, the reagents are effective with old as well as fresh fingerprints. Based on this technology Ciencia is developing a number of products including reagents and imaging instrumentation targeted to the forensics, national security and public safety markets.