This document provides an overview of latent fingerprint structure, composition, and development methods. It discusses the basic ridge patterns that make up fingerprints, as well as the organic and inorganic constituents of fingerprint residue. Common visualization techniques are described, including dusting, ninhydrin chemical development, and cyanoacrylate fuming. The document then focuses on thermal development of fingerprints, noting early attempts using household irons and furnaces. Recent research has found thermal development may help fingerprints become visible through fluorescence or charring, though the exact mechanisms are still unknown and likely involve eccrine secretions and amino acid decomposition products.

1. 2013
UOIT
Eric Cameron Sudar
100343489
ENHANCEMENT OF
LATENT FINGEPRINTS
ON DIFFERING SPECIES
OF WOOD USING
THERMAL
DEVELOPMENT

2. 1
Introduction
1.0 Fingerprint Structure and Formation
Fingerprints are the patterns of almost parallel ridge and valleys along with their minutiae
found on the epidermis of fingertips. The minutiae are structures such as ridge endings, island
ridges, crossovers, spurs, lakes and ridge bifurcations (Cao, K., Li, P., Tao, X., Tian, J., Yang,
X., & Zang, Y., 2010; Gaensslen & Lee, 2001, Kucken & Newell, 2004 ). At the 10th
week of
pregnancy, primary ridges start to form in the epidermis. Fingerprint development continues up
to the 17th
week of pregnancy where the fingerprint patterns and details become fixed for life and
visible in later weeks (Newell & Kucken, 2004).
Fingerprints contain features called singular points in where the directionality of the
ridges gradually changes. Two types of singular points are cores and deltas (Haung et al., 2007).
These small structures contribute to an overall pattern known as a whorl, loop or arch. These
patterns and structures are used in forensic science as a means of identification (Newell &
Kucken, 2004). There are some variations within these patterns such as tented or plain arches as
well as ulnar or radial loops. There are also patterns that are a combination of the whorls, arches
and loops. There has never been an identical set of ridge patterns found which makes the use of
fingerprints an ideal means of identifying individuals (Gaenslen & Lee, 2001).
Figure 1: Fingerprint Patterns: a) Whorl (W) , b) Loop, and c) Arch. Deltas (V) and Core (X) are
also shown. (Kucken & Newell, 2004)

3. 2
1.1 Fingerprint Constituents
Fingerprint residue contains both organic and inorganic substances. Aside from
contaminants which may be present on the skin at time of contact, there are natural substances
produced by the body that contribute to the composition of the fingerprint residue. For instance,
secretory glands such as eccrine and sebaceous glands contribute to fingerprint residue. The
eccrine glands contribute mostly water but also polypeptides, proteins, amino acids, and
inorganic ions. The sebaceous glands contribute lipids, waxes and sterols to the fingerprint
residue (Girod et al., 2012; Jelly et al., 2009).
There are a number of factors that influence the composition of fingerprint residues.
Factors such as deposition pressure, contact duration, donor diet, and surface characteristics are
only some of which influence the initial composition of fingerprint residues. Time after
deposition must also be taken into account as the composition changes over time. The aging of
fingerprints and change of their composition is often studied in an attempt to develop or improve
fingerprint development techniques, or develop methods for dating fingerprints (Girod et al.,
2012). Ageing of a fingerprint can be attributed to evaporation of volatile components, oxidation
or bacterial action (Jelly et al., 2009).
1.2 Fingerprint Visualization and Development Methods
Latent Fingerprints are invisible prints which require development to be observed.
Development techniques may include physical, chemical or optical enhancements. Each
technique comes with its own advantages and limitations (Houck & Siegel, 2011).
1.2.1 Luminescence detection using Lasers
In the late 1970’s, lasers were proposed as a method of observing latent fingerprints
(Champod, C., Lennard, C., Margot, P., & Stoilovic, M., 2004). This method incorporates the
use of lasers such as argon, copper vapor or neodymium-yttrium/arsenide/gallium lasers which is
an optical enhancement method (Houck & Siegel, 2011). To visualize fingerprints with this
method, light of a particular wavelength illuminates the surface through filtered goggles. The
advantages of this method are that it is non-destructive and is can be used on surfaces such as

4. 3
skin, some plastics and metal surfaces (Houck & Siegel, 2011). However, this method has a low
success rate in the field and cannot be used on luminescent surfaces. It is suggested to be used
first regardless of its effectiveness because it is a non-destructive technique (Champod et al.,
2004).
1.2.2 Fingerprint Dusting
Fingerprint dusting is a physical method that utilizes brushes and powders to reveal latent
prints (Houck & Siegel, 2011). Fingerprint dusting was first used in the last decade of the 19th
century. The powder dusting method involves the application of a fine powder that adheres to the
moisture and oily components of the fingerprint residue by a pressure deficit mechanism and
electrostatic attraction. A pressure deficit is generated inside a droplet of sweat due to the
curvature of the meniscus and its contact with the lower side of the powder particle. The
electrostatic attraction is created through frictional charges. When choosing a dusting powder,
the properties should be considered such that the powder does not react with the surface or be
strongly attracted to it. Also the color of powder should be chosen to give the highest level of
contrast to the surface. As the method can involve the contact of a brush to the print, there is a
destructive effect however other methods may be instead. The magna-brush is a magnetized
applicator that forms a brush when it attracts the magna-powder, coarse iron particles or flakes
carrying the non-magnetic formulation. The benefit of this method is that the applicator can be
used to clean up the excess powder from the print. Regular powders are composed of an adhesive
such as starch, rosin or silica gel as well as a colorant which tends to be an inorganic salt or
organic derivative. The benefits of the dusting method are that it is easy to use, cheap, has non-
toxic options and can be used on most non-porous surfaces. This method is not recommended for
porous surfaces (Kaur & Sodhi, 2001).
1.2.3 Ninhydrin
Ninhydrin is a chemical enhancement method that relies on the slow reaction with amino
acids to create Ruhemann’s Purple (Jelly, R., Lennard, C., Lewis, S.W., Lim, K.F., & Patton,
E.L.T., 2009). The reaction can be accelerated by performing the reaction in heat and humid
conditions. This chemical can be applied by spraying, painting or dipping. The print that is
developed appears bluish-purple (Houck & Siegel, 2011). Jelly et al. (2009) stated that collective

5. 4
opinions suggest it appears most likely that the color generated by this reaction is the same
regardless of the type of amino acid used. The reaction mechanism can be seen in Figure 2.
Though Ninhydrin was discovered in 1910 by Siegfried Ruhemann, it was not until the 1950’s
when its use was suggested for development of latent fingerprints. The formulation of Ninhydrin
is about 0.5% (w/v) while taking 24-48 hours to react in 50-80% humidity. Ninhydrin is the
primary chemical reagent used for the development of latent fingerprints on porous surfaces.
Since Ninhydrin produces a final product that is purple, it limits the surfaces that this method can
be applied to by itself due to lack of contrast. However this can be overcome with the use of
secondary salt treatment and optical enhancements after application (Jelly et al., 2009).
Figure 2: Ninhydrin reaction with generic (R) amino acid group (Jelly et al., 2009)
1.2.4 Cyanoacrylate Fuming
Cyanoacrylate fuming is a chemical method that utilizes alkyl-2-cyanoacrylate, otherwise
known as Super Glue, to develop latent fingerprints. In 1978, the Criminal Identification
Division of the Japanese National Police Agency created a procedure to use this method
(Gaensslen & Lee, 2001). The method involves turning the colorless liquid into a vapor that
reacts with the eccrine and sebaceous components of the fingerprint reside to produce a hard,
white polycyanoacrylate. The cyanoacrylate vapor is also reactive with moisture. It has been

6. 5
found that too little moisture can produce prints of low contrast which is why a small container
of water is placed with the prints to provide sufficient amount of moisture (Champod et al.,
2004). To vaporize the liquid, the liquid is heated to about 80 to 100˚C. When the cyanoacrylate
comes in contact with the fingerprint constituents, a polymerization reaction occurs. The reaction
mechanism can be seen in Figure 3. Cyanoacrylate fuming is effective for development of
fingerprints on plastics, styrofoam, aluminum foil, rubber, copper, cellophane, smooth rocks as
well as finished and unfinished wood (Gaensslen & Lee, 2001). This method does not yield
prints that are high in contrast which may necessitate further development by histological dyes or
visualization using an optical enhancement method (Gaensslen & Lee, 2001).
Figure 3: Polymerization reaction (Day, J.S., Dobrowski, S.A., Edwards, H.G.M., & Voice, A.M., 2004)
Literature Review
1.3 Thermal Development of Fingerprints
Thermal development of fingerprints is a method that utilizes heat as a means of making
fingerprints more visible on surfaces such as paper, wood and masking tape. Research in thermal
development of fingerprints dates back to the 1940’s (Brown et al., 2011). Earlier attempts
involved the use of a common household iron. The process of thermal development has been of

7. 6
aid in arson cases where the heat from the fire caused the suspect’s latent fingerprint(s) to
become visible by charring on the remaining debris such as paper (Olsen, R.D., 1978). It was not
considered a practical method as the results were not as good or predictable as developed prints
from using ninhydrin or iodine fuming (Olsen, R.D., 1978). Later research in the 1980’s, used an
electric furnace but was still found to be less effective than using Ninhydrin (Brown et al., 2011).
Recently, some researchers believe that this development method has potential to be used in the
field and has the additional benefits of being safe as well as cheap (Brown et al., 2009).
Almog & Marmur (1981) hoped that if the fingerprints were developed further to their
charring stage that information regarding the age of the prints could be obtained. It was found
that as the age of the fingerprints increased the general quality of the developed prints decreased
by an observed gradual blurring. This suggested a migration of organic compounds in the surface
(Almog & Marmur, 1981). However, there is no current research suggesting a means of
determining the age of a fingerprint using the thermal development method.
1.4 Thermal Development Process
The process by which thermal development operates is currently unknown but there are
some findings that show what is involved. Almog & Marmur (1981) believed that organic
constituents were involved. In a 2009 study conducted by Brown et al., both the initial
fluorescence stage and charring stage were kept in mind as they investigated the mechanism
behind the fluorescence effect. Brown et al. suggested that the development process of the
fingerprint was not a result of a chemical reaction with paper and fingerprint constituents but
instead the constituents act to increase the heating of the paper. This was suggested because the
authors observed that the paper underwent the same changes in fluorescence without the
fingerprint constituents but at a slower rate. The authors, in this study, also suggested that eccrine
and sebaceous materials are the most likely candidates for this process. Further research
conducted by Bleay et al. (2010), in the second part of their experiment concluded that
fluorescence is correlated to the eccrine material. Furthermore the authors suggested some
alternative cause of fluorescence. They suggested that two reaction products of amino acid
decomposition or their intermediates could account for the fluorescence in paper after heating.
They also suggested that the fluorescence could be attributed to sodium chloride and urea or