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forensicfingerprint · 4 years

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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 fingerprint 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 fingerprint 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 fingerprint 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 fingerprint 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 fingerprint . 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 print.

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.

A forensic expert always applied his experience and scientific skills to use the better technique for 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.🙏

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