Study on Efficiency of Alternate Light Source for Detection of Latent Fingerprints
Peter Kiran A* and Dakshinamurthy Sridevi
Department of Forensic Science, Jain University, India
Submission: July 06, 2018;Published: July 12, 2018
*Corresponding author: Peter Kiran A, Department of Forensic Science, Jain University, India, Tele: 8971435885; Email: firstname.lastname@example.org
How to cite this article: Peter Kiran A, Dakshinamurthy S. Study on Efficiency of Alternate Light Source for Detection of Latent Fingerprints. J Forensic Sci & Criminal Inves 2018; 9(5): 555774. DOI:10.19080/JFSCI.2018.09.555774.
Latent prints being the most common form of evidence at a crime scene, links the person directly to the crime scene and needs to be detected and collected using a non-destructive method which includes the use of light sources and different illumination methods. It is known that detecting fresh latent prints at a crime scene using light sources is quite easy, but using the light sources to detect latent prints which have been deposited over a period of time is a challenge. The purpose of the current study is to determine how long Alternate Light Source (ALS) can be used as an effective method in detecting latent prints which have been deposited on the surface over a period of time and by evaluating the quality of the latent prints and determining the best light source and the best illumination method for detecting and photographing the latent prints.
Fingerprint is defined as the raised ridges, which form accidentally during the development of the foetus, that cover the whole of the inner surface of the hand and the underside of the soles of the feet. The images of the ridges form a fingerprint. Fingerprints are unique and are still considered to be the best form of personal identification for criminal investigation purposes. They help in proving the presence or absence of a person at a crime scene. Fingerprints found at crime scenes can be categorized by some examiners as patent, plastic or latent impressions. A latent finger mark is an invisible print which needs to be developed to make it visible and they are the most common form of fingerprint evidence. Latent fingerprints are a hidden record on materials formed by perspiration and oil from the internal finger the form of ridges and furrows during friction or contact. Three primary glands contribute to the production of sweat: The sudoriferous glands (eccrine and apocrine) and the sebaceous glands. Latent print can be found on different surfaces classified as porous, non-porous, semi-porous and textured surfaces.
The following general procedures are appropriate during a systematic search for latent fingerprint evidence:
a. Visual inspection with a bright light, forensic light source, or laser
b. Sequential latent print processing
c. Documentation of developed prints at each step
Detection of latent prints being the primary step towards processing of latent prints, light sources are very helpful. In addition, prints developed using a physical or chemical process can generally be further enhanced using an appropriate light source such as ultraviolet light (UV), Infrared light (IR), high intensity white light, laser, led and Alternate Light Source (ALS) or Forensic Light Source (FLS). Alternate light source (ALS) is a portable, tunable multi waveband light source. It is made up of a powerful lamp containing the ultra-violet, visible and infrared components of light. It then filters down the light into individual colour bands (wavelengths) that enhance the visualization of evidence.
A study on the overview of the current techniques available to law enforcements agencies for detection and enhancement of latent finger marks on different surfaces conclude that UV reflection techniques have proven to be useful on a number of surfaces when short wave UV light is used (Dr. Chris Lennard). A study on the development of latent prints that involve using anti stokes phosphors requires an elimination source that emits infrared radiations. It was concluded when fingerprints were developed with UP54 pigments and photographed with the use of UV radiations, white light and infrared radiations best
results were obtained with infrared illuminations, which caused
the illumination of fingerprint alone and not the background
(Bogdan Drabarek, Antoni Siejca, Jaroslav Muezzins and Barbara
The article on “Finger mark examination techniques
within scope of ISO 17025” concludes that on some nonporous
surfaces, the number of unique marks found by visual
examination with a white light source was much higher. For the
purpose of photography of the evidence under different lighting
sources, different illuminations methods are used, which include
45-degree lighting, direct reflective lighting, diffused lighting,
oblique lighting, bounce lighting, transmitted lighting and front
directional or axial lighting. Once the print is detected it has to
be photographed and generally for crime scene photography a
DSLR or 35 mm film camera is used. An article states that coaxial
lighting yielding superior photographic fingerprint image
compared to the image produced by the trans-illumination and
oblique lighting (Z Ziv, E Springer).
Photography is the science, art and practice of creating
durable images. Photographs help creating a permanent
visual record of the crime scene in the state in which it was
originally found. They can act as triggers for both witnesses
and investigators when trying to remember details of the event
and scene. Such photographs will also be greatly beneficial
in reconstructing the events which took place. Finally, the
photographs taken at the scene can be called upon in court to
support verbal and physical evidence, and give jurors a clear
image of the crime.
The study was carried out by first depositing fingerprints
on different surfaces such as aluminum utensil, ceramic tile,
glass, paper, foam, painted and unpainted wood. Light sources
such as white light, ultraviolet light (UV) and Infrared Light
(IR) were used to detect the latent print at different angles top
angle, oblique angle and transmitted light illumination (only
for surface glass). The quality of fingerprints were observed
and photographed immediately. The latent prints were kept
exposed to normal room temperature and atmosphere and the
light sources were used to observe and rate the quality of latent
prints on a daily basis for a period of eighteen (18) days. Finally
the data was analyzed and compared to determine the best light
source for the detection of latent fingerprints.
For the surface ceramic tile, the researcher has observed
that at top angle illumination the quality of the latent print
under ultraviolet light was observed to be good for the first
couple of days and average for the rest of the days; consistently
good under white light and under infrared light source it was
observed to be good and only in the later stages it was observed
to be average. At oblique angle illumination, the quality of the
latent print was observed to be good for the first couple of days
but not detectable the rest of the days; under white light the
results fluctuated but later gradually reduced to average quality
prints and then bad quality prints; under infrared light source
the print is not detectable for most of the days (Figure 1).
For the surface metal (Al), the researcher has observed
that at top angle illumination, with ultraviolet light source, the
quality of the latent print was observed to be good in the start
and then degraded to average quality prints; under white light
source and infrared light source the quality of the prints was
observed to be consistently good. At oblique angle illumination,
under ultraviolet light source the quality of the latent print was
observed to be good in the start then degraded to average quality
prints; under white light source and infrared light source the
observations fluctuated between good and average (Figure 2).
For the surface glass the researcher has observed that at top
angle illumination, with ultraviolet light source, the latent print
quality was observed to be good and then gradually degraded
to average and then bad; under white light source and infrared
light source the quality of the prints were consistently good. At
oblique angle illumination, under ultraviolet light, white light
and infrared light the quality of the latent print was observed to
be good and then was observed to gradually change to average
and bad quality prints. At transmitted light illumination, under
ultraviolet light the quality of the latent print was observed to be good and only in the later stages average quality prints were
observed; under white light source the print was observed to be
consistently good and under infrared light source the quality of
the prints were observed to good and in the later stages average
quality prints were observed (Figures 3 & 4).
a. On the surfaces paper, foam, painted wood and
unpainted wood, the latent prints were not detectable with
light sources right from the first day.
b. On ceramic tile, at top angle illumination, white light is
the best light source and at oblique angle illumination white
light source is better.
c. On a metal surface like aluminum, at top angle
illumination, white light source and infrared light source
are the best but at oblique angle illumination infrared light
source is better.
d. On glass surface, at top angle illumination and
transmitted light illumination, white light source and
infrared light source are the best, but at oblique angle
illumination infrared light source is better.
e. When using white light source, top angle illumination
is the best and under infrared light source also top angle
illumination is the best but in certain cases oblique angle
is better for the photography of the latent prints deposited
over a period of time. Ultraviolet light source is the least
effective light source for detecting latent prints when used
for detecting long duration latent prints [1-8].