Latent fingerprints
Crime scene Fingerprints are of three type -
Plastic fingerprints
Visible fingerprints and
Latent fingerprints
When we talked about development of fingerprints at crime scene. We mainly
talked about latent fingerprints. Latent means hidden. There are two processes
for development of fingerprints at crime scene -
Physical method - After examination of crime scene an expert locate the
latent fingerprints. For the development of latent fingerprints there are variety
of fine fingerprint brushes and many types of fingerprints powders are available .
An expert always use powder in contrast to the surface on which
the latent fingerprints present. Selection of powder depends upon the
Nature of surface (Porous , semi-porous , nonporous)
Texture of surface (smooth and rough)
Condition (dry and wet) and color of surface.
The powder with a fine brush first lightly applied to the latent fingerprints and
when ridges start appearing then applied the more powder. The brush applied in
one direction and when ridges seen then applied as the fingerprint pattern appeared.
After development of latent fingerprints the expert marking the print with date and
sign and then it should be photographed . The mostly used fingerprints powders are
black and grey powders. For development on multicolored surfaces fluorescent powders
should be used.
Chemical methods - Fingerprint impression contains salt , proteins , amino acids ,
lipids and oil. chemicals reacts with these substances and reveal the
latent fingerprint. Latent fingerprints development by chemical methods includes
some old techniques such as -
Iodine fuming - Oldest technique. Its react with the fat and oil deposits of fingerprint and print visible in yellowish brown color. Starch solution is used for permanent fixation of print. This technique used on papers , clothes and on greasy prints.
Ninhydrine technique - Ninhydrin reacts with amino acids of the latent fingerprints . This is also useful on very old fingerprints .
Silver nitrate technique - This technique is useful on papers card boards , cloths and raw unpainted wood.
Cynoacrylate fuming - This technique used on plastics bags , aluminium foils , electrical tape , unfinished wood , rubber cellophane etc.
Vacuum metal deposition - In this technique results are good even on old degraded fingerprints.
Nano technology - Antibodies "anti-cotinine" binds to the amino acids of the print.
Some other chemicals developers technique are also used as -
DFO - It is 1,8 diazafluoren-9 one. Its a ninhydrin analogue and used on porous surfaces like paper card boards etc. It reacts with amino acids present on the latent fingerprints .
Sticky side powder - It is used on adhesive side of tapes. Its very economical and effective.
Physical developer - It is used on dry and wet porous items like clay based products , paper articles and on adhesive tapes. Its acts on the lipid and fatty acids of sweat.
Small particle reagent - it's a suspension of fine molybdenum disulfide particles in a surface active solution. It is used on moist non porous surfaces.
In recent years application of light sources for development of latent fingerprints are increases . Its
includes high intensity white light , UV light , laser , infrared light , LED , forensic light source or
alternate light source.
conclusion - A forensic expert always applied his experience and scientific skills to use the better
technique for latent fingerprints development. There are some factors on which the application of
above techniques depends -
Which type of Crime occurred
Type of Surface and
Size of articles .
We will discuss about all chemical methods in details on our next post .🙏
MR. DEEPAK PAWAR has been working as Finger Print Expert / Police Officer in Finger Print Bureau , Delhi Police at New Delhi since 2001 . He is the senior most Finger Print Expert , attending / visited several scene of crime and solved many crime cases .He has passed M.Sc (Chemistry) and he is the Member of International Association of Identification . He is the Member of Delhi Police welfare association . He is supervising the Forensic , New Delhi District , Mobile Crime Team . He is one of the Expert in the Special Investigation Team held for investigation of important cases . He has been giving fingerprint proficient training to Delhi Police personnel's . He has been Presented / giving lectures on topics related to forensic science . He is also making examination paper of Finger Print proficient course . He is awarded with Police Medal by MHA and Delhi Police.