Advances in Fingerprint Technology.pdf

There were four principal milestones in this evolution: (1) the introduction
of the nonflammable formulation, NFN (nonflammable ninhydrin, which is
now banned); (2) the introduction to fingerprint development of lasers and
alternate light sources; (3) the secondary treatment with metal salts to produce
fluorescent impressions; and, (4) the preparation and examination of
ninhydrin analogues, whose crowning achievements were the introduction
of DFO and the recent discovery of the potential of 1,2-indanedione. These
processes remarkably improved the ability of law-enforcement agencies to
detect latent fingerprints on porous surfaces such as paper and cardboard.
Indeed, over the past few years many reports have appeared in the forensic
science literature describing actual cases of fingerprint detection that would
have been impossible only a few years ago. Ninhydrin is currently used in a
sequence in advanced fingerprint laboratories. To achieve best results, it is
applied after DFO and before PD.
The aim of this chapter is to survey the use of ninhydrin as a fingerprint
reagent, with emphasis on progress in recent years. Two sections, “Comparison
with Other Reagents” and “Miscellaneous Considerations,” that
appeared in the previous edition of Advances in Fingerprint Technology do
not appear separately this time.
Chemical Development of Latent Fingerprints
Latent fingerprints on porous surfaces can be visualized by numerous chemical
methods. Many of these can be regarded as purely theoretical because
they have no practical use in the forensic science laboratory. On the other
hand, no single technique for recovering latent prints has universal applications
under all circumstances, and the choice of method may vary from case
to case. 1,2 In its narrow definition, the chemical development of latent fingerprints
is expressed by a visual chemical reaction between the reagent and
one or more of the constituents of human perspiration, to yield a colored,
luminescent, or radioactive product. In this manner the ridge detail becomes
visible and the prints can be photographed and further manipulated.
Amino acids are the most desirable substrate of the palmar sweat components
to be developed on paper. They are always present in human perspiration
and they produce colored and luminescent products with a variety
of reagents. Due to their high affinity for cellulose, they do not migrate with
age (like urea or inorganic salts) and can be developed even after a long
period of time. Cases have been reported in which latent prints have been
detected and identified on paper specimens known to have been handled
several years previously. 3,4 Amino acids on paper can be visualized by a variety
of chemical reagents such as fluorescamine, 5-7 alloxan, 3,8 o-phthalaldehyde 6,7