Advances in Fingerprint Technology.pdf

Specially designed cabinets for chemical development of fingerprints
under controlled conditions of temperature and humidity have become a
major tool in most advanced forensic laboratories.
Secondary Treatment with Metal Salts: Fingerprint Detection
Aided by Lasers and Alternate Light Sources
Despite the fact that ninhydrin is regarded as “the latent fingerprint examiner’s
workhorse,” 73 it suffers from the following disadvantages and limitations:
1. The chemical process is slow.
2. Many paper samples contain ninhydrin-positive materials that give
rise to the formation of intense background coloration and can
obscure the developed prints. 42,46,74 *
3. Sensitivity is not always sufficiently high. Not all individuals excrete
sufficient perspiration to leave identifiable prints using those methods
known today. 43,46,74
4. The contrast of ninhydrin-developed prints is often insufficient 46,48 on
certain dark surfaces.
5. Prints developed with ninhydrin are not permanent. (There is debate
among fingerprint practitioners as to whether or not this is a real
problem. 43,59 )
Hence, ninhydrin application to a document does not guarantee the development
of latent fingerprints, although it may be known that the document
was indeed touched by a certain person. 43 Considerable research efforts have
been made toward the improvement of some of these drawbacks since the
first application of ninhydrin to casework. In the beginning, most researchers
focused on attempts to improve the formulations and working conditions.
The crowning achievement of this approach was the development of the NFN
formulation in 1974. 42 In 1977, the discovery of the potential of lasers for
forensic science applications opened a new era in fingerprint technology. In
that year, Dalrymple, Duff, and Menzel reported that latent fingerprints on
various surfaces could be visualized by illumination with an argon-ion laser
and observation through an appropriate filter. 75 Later studies showed that
the percentage of latent prints detectable by their inherent luminescence under
laser illumination was not very high, and researchers started to explore the
possibility of combining lasers with fingerprint reagents. 12 This approach led to
the next leap forward in the use of ninhydrin for fingerprint development.
* These background colors arise from the presence of natural organic constituents in the
raw materials or from the various sizing or coating materials used to improve the surface
properties (e.g., rag-based high-quality writing paper, 46 bank notes [where melamine has
been used as a plasticizer], and some checks and postal money orders). 72