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Visualization of Latent Fingerprints Using Neutral Alumina as an
Inexpensive Fingerprint Developing Powder
V Ramanan1, M Nirmala2
Abstract
The unicity, permanency, and generality of fingerprints make them as a reliable identification feature in crime and
civil cases all over the globe. Various methods are available for the detection of latent fingerprint. Of them, powder
dusting is a simplest and most commonly used procedure. Although several powders has been demonstrated earlier
as visualization agents of latent fingerprints, in some context, they are expensive, toxic, and are not easily accessible
as they usually composed of various materials. In this study, we have introduced neutral alumina, commonly used
in thin layer chromatography as a stationary phase, as a new fingerprint visualizing agent. Neutral alumina is a
cheap, easily available and accessible (one of the most common laboratory consumables), non-toxic, convenient
material. In this study, the effectiveness of alumina as a fingerprint powder has been demonstrated on sixteen
various substrates of different properties. The results revealed that the alumina powder can be used as an efficient
alternative for other costly commercial powders. The alumina-developed friction ridges were also viewed with
the aid of confocal laser scanning microscope and the results are discussed in this article. The alumina-developed
fingerprint offers the possibility of extracting level 2 and level 3 features too. Context: The main objective of this
work is to identify cheap, non-toxic, and easily accessible material for fingerprint detection as efficient alternative
to costly and toxic commercial fingerprint powders. Aims: The aim of this work is to explore the efficiency of
neutral alumina as a cheap and non-toxic fingerprint powder particularly in the scarcity of commercial powders.
Results: Sixteen substrates with varying surface, color, and nature were chosen to deposit the fingerprints and
their efficiency of development on the application of neutral alumina powder was explored. Most of the alumina-
developed substrates were showed excellent contrast and visibility. Conclusions: The neutral alumina powder can
be an effective and inexpensive substitute for other commonly used fingerprint powders particularly in the case of
shortage.
Keywords: Powder dusting; Confocal laser scanning microscopy; Sweat pores; Ridge density; Minutiae; Ridge
spacing.
Author's Affi liation: 1Junior Scientifi c Offi cer, Forensic Sciences Department, Government of Tamil Nadu, Chennai,
India, 2DS Kothari Post Doctoral Research Fellow, National Centre for Ultrafast Processes, University of Madras,
Tamil Nadu, Chennai, India.
Correspondence: V Ramanan, Junior Scientifi c Offi cer, Forensic Sciences Department, Government of Tamil Nadu,
Chennai, India.
E-mail: ramanan89chem@gmail.com
Original Article International Journal of Forensic Science
Volume 3 Number 1, January–June 2020
How to cite this article:
V Ramanan, M Nirmala. Visualization of Latent Fingerprints Using Neutral Alumina as an Inexpensive Fingerprint
Developing Powder. International Journal of Forensic Science. 2020;3(1):5–10.
Introduction
Application of fi ngerprints to personal identifi cation
in crime investigations has been in practice over a
century.1 In fact, the importance of fi ngerprints as
identity marks has been known from ancient times
when fi ngerprint impressions had been used as
a seal.2 For example, contracts were signed using
fi ngerprints in Babylon in about 200 BC.3 “Nadi
Astrology” is one of the ancient arts of India which
said to predict one’s past, present and future using
palmprint features.4 In forensic investigations, the
fi ngerprints are important physical evidences and
6
International Journal of Forensic Science / Volume 3 Number 1 / January–June 2020
are available in most of the crime scenes. Practically,
it is a diffi cult job for a forensic examiner to identify,
develop and lift the latent fi ngerprints found in
a crime scene.5 Most of the latent fi ngerprints
are found in damaged or smeared conditions.
Some of the crucial fi ngerprints are only partially
available in many cases. Many different methods
and strategies have been developed so far to obtain
the latent fi ngerprints for crime investigations.6-9
Majority of them are based on the natural secretions
of the palm from the four different types of
glands namely, eccrine, apocrine, apoeccrine, and
sebaceous. Each gland secretes a slightly different
blend of chemical components.10-14 Although,
several advancements have been developed to
detect the invisible fi ngerprints, powder dusting
method is the traditional one and one of the earlier
references15 dating back to 1891. The application of
fi nely ground material and the subsequent removal
of their excess by means of blowing, tapping
or brushing has been the universal method for
developing the latent fi ngerprints since the early
days of the fi ngerprint technology.16 The strategy
purely depends on the physical adhesion of the
powders on the aqueous and oily deposits on the
friction ridges. Thousands of powder formulations
have been devised so far by various researchers
for the detection of latent fi ngerprints which are
varying by color, chemical composition, size and
shape of the particles, etc.5-7,17 Some traditional
powders, bears noxious constituents and pose
potential health risks and some of them are costly.
Hence, the search for the cheaper, easily available,
non-toxic powder for latent fi ngerprint detection is
keeps pursuing.
As a result, many non-conventional powders
such as turmeric18, food powders19,20 and festival
colors20 have been demonstrated as fi ngerprint
powders. Rakesh and co-workers21 have applied
Silica Gel G as a cheap, easily available fi ngerprint
developing powder. They have reported that the
results are comparable with the other conventional
powders.
In the present study, we have recognized the
Neutral Aluminium Oxide G (TLC Grade) as
a new material for the visualization of latent
fi ngerprints. Aluminium oxide or Alumina is a
cheap, non-toxic material and is easily available.
Of the three variants of the alumina namely, acidic,
basic, and neutral, the neutral alumina is used in
this work. Gypsum is added as the binder in the
commercially available neutral alumina G for
TLC applications. The structure of the neutral
alumina is complicated. However, it is thought
to have the structure portrayed in the Fig. 1. The
aluminium atoms are connected with oxygen
atoms which can form hydrogen bonds with
water and other hydroxyl compounds.22-24 The
polar nature of the alumina surface attracts other
polar compounds by electrostatic or hydrogen
bonding interactions or through Van der Walls
forces of attractions. Moreover, alumina as a
Lewis acid, can form coordinate bonds with lone
pair containing hetero atoms such as nitrogen and
oxygen25 (amino acids and hydroxyl compounds
for example) present in the natural secretions of
fi ngers. It is well known that the natural secretions
of palm contain 98 % water and many amino acids.
Both these emanations can interact well with the
alumina. The interactive groups on the surface of
neutral alumina in contact with aqueous solvent
are mostly hydroxyl groups as analogous to the
interaction between hydroxyl groups and silica gel.
On the other hand, the polar surface of the alumina
can form electrostatic interactions with the polar
amino acids. The Scheme 1 illustrates some of the
possible interactions between the neutral alumina
and fi ngerprint secretions such as amino acids
and hydroxyl compounds. To our knowledge,
no reports have been published so far on the
application of alumina as a fi ngerprint powder. On
this context, we have employed the neutral alumina
G to visualize latent fi ngerprints and presented the
results here. We hope these fi ndings will be useful
to the forensic fi ngerprint experts in handling the
latent fi ngerprints.
Materials and Methods
The neutral aluminium oxide G for TLC (with
binder) was purchased from Sisco Research
Laboratories Pvt. Ltd. Common household
articles were selected as the adsorbents for latent
fi ngerprints. The experiments were carried out in
the month of December which is the winter season
in India. The local temperature and humidity were
30°C to 32ºC and 72 % to 77 % respectively. The
volunteers washed and dried their hands before
an hour prior to deposit their fi ngerprints. While
depositing the fi ngerprints the volunteers were
slightly sweating. The alumina powder was applied
on the surface under investigation and pressed
gently. The excess powders were removed by
tapping and blowing. The developed fi ngerprints
were photographed using a smart phone (brand:
oppo, model: realme 1) with the camera capacity of
13 MP. The ridge spacing and the pore morphology
of alumina developed fi ngerprints were viewed
V Ramanan, M Nirmala / Visualization of Latent Fingerprints Using Neutral Alumina as an Inexpensive Fingerprint
Developing Powder
7
International Journal of Forensic Science / Volume 3 Number 1 / January–June 2020
under a confocal microscope (LEICA DMIRE2)
with the laser wavelength of 633 nm. 10x objective
was used to view the fi ngerprint.
Sixteen various porous and non-porous surfaces
were used in this work on which the fi ngerprints
were deposited. The non-porous or smooth surfaces
used in this work are a glass microscopic plate, top
surface of a watch, a brown color plastic bottle, a
black color belt buckle, wind shield of a helmet,
non-writable surface of a compact disc (CD), touch
screen of a smart phone, a stainless steel (SS) vessel,
a glass jar, a brown color glass bottle, a multicolor
identity card, and a SS pen drive. The developed
latent fi ngerprints are shown in the Fig. 2 (a)-(l).
The porous / textured / engraved surfaces
employed in this study are a nickel brass (German
silver) currency coin, a black color plastic mouse, a
SS lock, engraved area of a CD, a SS currency coin,
a multicolored match box, a currency paper, and a
jewellery cloth box. The corresponding developed
latent fi ngerprints are presented in the Fig. 3 (a)-(h).
Results and Discussions
The friction ridges of alumina-developed latent
fi ngerprints on non-porous surfaces are very
clearly or fairly visible in all the cases. Even those
developed on porous surfaces also exhibit a good
distinction between the friction ridges and the
background. Alumina-developed fi ngerprints are
visible in various colored surfaces. Even, it showed
good visibility in white backgrounds Fig. 2 (f)
and (k). The multicolor cardboard surface of the
match box also generates a readable fi ngerprint on
application of the alumina powder (Fig. 3(f)). On
the other hand, negative results are obtained for
currency paper (Fig. 3(g)) and jewellery cloth box
(Fig. 3(h)) due to poor contrast.
The minutiae details can be clearly observed in
most of the fi ngerprints developed by alumina. For
example, the Fig. 2 (a) is enlarged to observe the
minutiae details. On enlarging, many minutiae
features such as dot, island, enclosures, bifurcations,
trifurcation, delta, spur, disconnection, ridge
endings, lake, ridge crossover, and core are clearly
observed and are presented in Fig. 4. Hence, it is
clear that “Level 2” information can be extracted
from the fi ngerprints developed by alumina
powder. The fi ngerprint characteristics can be
divided in to three levels.27 Level 1 refers to the
general pattern formed by the fl ow of ridges on
the papillary surface, singular points and types.
These are macro details of a fi ngerprint. The level
2 features are due to major deviations on the ridge
patterns such as bifurcation, ridge ending, dot, etc.
These distinct points are referred as “minutiae” or
“Galton characteristics”. On the other hand, the
level 3 features include all dimensional attributes
of the ridge path deviation, such as alignment
and shape of each ridge units, shapes and relative
positions of pores, etc. The pore morphological
features are micro level details of a fi ngerprint. It
is worth to note that a large number of sweat pores
are obviously visible all over the Fig. 4 especially
around the core area. In most of the images shown
in the Fig.2 and 3, the sweat pores are clearly
visible especially in the fi ngerprints developed on
microscopic glass slide, top surface of the watch,
non-writable surface of the CD, and the nickel brass
currency coin. Hence, these fi ngerprints could also
provide level 3 information.
In this context, the fi ngerprint in Fig. 4 is digitally
enlarged at a selected area around its core region
and the contrast is digitally increased to 50 %. The
resulting image is showed as Fig. 5. The enlarged
Fig. 5 clearly reveals the presence of many pores
on the friction ridges. Some of the pores are circled
to highlight. From the image, the relative positions
of the pores and the pore morphology such as its
shape and relative size can be extracted.
The Fig. 4 also reveals a very good contrast
between the friction ridges and the furrow. To
explore the micro level details more clearly, we
have viewed the alumina-developed fi ngerprint
using a confocal laser scanning microscope
(CLSM). Literatures are rarely available on the
visualization of fi ngerprints using CLSM. CLSM
is a very good tool to view micro dimensions with
a great resolution. The ridges were focused using
CLSM and photographed directly using a smart
phone and presented as Fig. 6 in which some of
the pores are encircled. Images of the developed
ridges recorded using CLSM are shown in Fig. 7
in different colors for the better visualization. The
pores can be visualized well in Fig. 7. The selective
adherence of neutral alumina on the ridges rather
than the furrow is also revealed well from Fig. 6
and 7. The spacings between the ridges were
measured and are shown in the Fig. 8. The average
ridge spacing in the area under investigation is
about 173.5 μm.
CLSM images can also provide quantitative
details about a fi ngerprint such as ridge density.
Ridge density can be defi ned as the number of
ridges per unit distance. The ridge density feature
fi nds its valuable application on partial fi ngerprints
which are the only fi ngerprints available in most
V Ramanan, M Nirmala / Visualization of Latent Fingerprints Using Neutral Alumina as an Inexpensive Fingerprint
Developing Powder
8
International Journal of Forensic Science / Volume 3 Number 1 / January–June 2020
of the crime scenes. The pattern class is obviously
indecisive in partial fi ngerprints and is indefi nite
for noisy fi ngerprints. In addition, some reports
even claim sex determination from fi ngerprint
ridge density.28-30
Fig. 1: Structure of neutral alumina.
Fig. 2: Alumina-developed fingerprints on smooth surfaces (a)
a glass microscopic plate, (b) top surface of a watch, (c) a brown
color plastic bottle, (d) a black color belt buckle, (e) wind shield
of a helmet, (f) non-writable surface of a compact disc (CD), (g)
touch screen of a smart phone, (h) a stainless steel (SS) vessel, (i)
a glass jar, (j) a brown color glass bottle, (k) a multicolor identity
card, and (l) a SS pen drive.
Fig. 3: Alumina-developed fingerprints on porous/textured/
engraved surfaces (a) a nickel brass (German silver) currency
coin, (b) a black color plastic mouse, (c) a SS lock, (d) engraved
area of a CD, (e) a SS currency coin, (f) a multicolored match box,
(g) a currency paper, and (h) a jewellery cloth box.
V Ramanan, M Nirmala / Visualization of Latent Fingerprints Using Neutral Alumina as an Inexpensive Fingerprint Developing
Powder
Fig. 4: Various minutiae points observed in an alumina-
developed fingerprint.
Fig. 5: Visualization of sweat pores on the digitally enlarged
alumina-developed fingerprint.
Fig. 6: Direct photograph of alumina developed friction ridges
focused using CLSM. Light green circles indicate pores.
9
International Journal of Forensic Science / Volume 3 Number 1 / January–June 2020
V Ramanan, M Nirmala \Visualization of Latent Fingerprints Using Neutral Alumina as an Inexpensive
Fingerprint Developing Powder
Fig. 7: CLSM images of alumina-developed finger
ridges using different color filters for better
visualization. The scale bar represents 179 μm.
Fig. 8: CLSM image revealing the distance between two parallel
friction ridges
Scheme 1: Illustration of some of the possible
interactions between neutral alumina and
fingerprint secretions such as amino acids and
hydroxyl compounds.
Conclusion
A cheap, easily available, non-toxic, easy to handle
material, neutral alumina was identified as a
new fingerprint powder and its application as a
fingerprint powder was demonstrated in this study.
Sixteen substrates with varying surface, color, and
nature were chosen to deposit the fingerprints and
their efficiency of development on the application
of neutral alumina powder was explored. Most of
the alumina-developed substrates were showed
excellent contrast and visibility. Confocal laser
scanning microscope was used to view the micro
level features of an alumina-developed fingerprint.
The possibility of extracting all the three level
information from the alumina-developed
fingerprints was discussed. The neutral alumina
powder can be an effective and inexpensive
substitute for other commonly used fingerprint
powders particularly in the case of shortage.
Acknowledgement
Dr. M. Nirmala thanks Dr. D.S. Kothari post
doctoral fellowship scheme (F.4-2/2006 (BSR)/
CH/18-19/0177) of University Grants Commission
(UGC) for financial assistance. Both the authors
thank Dr. C. Selvaraju, Director i/c, National Centre
for Ultrafast Processes, University of Madras for
his guidance in recording the CLSM images. Dr.
V. Ramanan thanks Tmt. A. Visalakshi, Deputy
Director and Tr. K. Manivannan, Assistant Director,
Forensic Sciences Department, Government of
Tamil Nadu, Chennai for their motivation and
support.
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