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