Forensic Science: Methods of examining fingerprint


Methods of examining fingerprint

The search of the fingerprints should be done in the systematic manner. The area or place where the fingerprint can be suspected should be searched properly and thoroughly. In the case of Sanjay and others v. State of Maharashtra (CRIMINAL APPEAL NO.2 OF 2012), the court held that the fingerprint can be studied when the investigation done to it is systematic and done properly. And in this case also the fingerprint was counted as circumstantial evidence. Those surfaces are mostly examined with oblique lighting and through this light the diffused light is avoided. And the semi dark place is preferable.

Magnifying glass is the most quality and useful way of locating the fingerprint. And polylight system is more convenient for searching the fingerprint. It is also easily portable.

There are many common techniques which are also used to trace the fingerprints. One is the powder development. This is mostly used to discover the latent fingerprint when it is tracked on the small surfaces. But they mostly fail in case if the old prints and the prints found on rough surfaces. There are many types where these powders are used to examine the fingerprint powder examination. Like for example, the grey powder is used for all the dark coloured surfaces. And in the same way, the black powder is used against light background. The fluorescent or anthracene powder is mostly used for the surfaces which is multi- coloured. These powders develop the fingerprint and then it is exposed to ultraviolet rays and then it is photographed. The developed fingerprints are prepared from the transparencies. The metallic powder and universal powder are only used when there is special situation. These powders are mostly used for the sticky powder. When there is the large area, the fingerprint is tracked from the metallic powder which is used with Magna brush facilities.

It should also be noted that the powder used should not be reactive and it should be dry, amorphous and it should be uniform consistent of flour. The powder technique is simple but it still needs to have expert experience to carry on investigation. Powdering should always do with the camel hair brush, and if it is not present, atomizers and automatic fingerprints spray devices are used as an alternative. It shall also be noted that the automatic sprayer is a boon where extensive searches are required. These powder methods are one of the easy and quick and almost automatic methods of tracing the fingerprint.

Another method is the chemical method which used to trace the fingerprint. The perspiration materials which are deposited by the fingerprint and which results in formation of the latent prints can also be traced by the chemical methods. For example, when the sodium chloride when treated with silver nitrate solution will result in formation of the silver chloride and which is insoluble. This chemical automatically gives the black colour exposure to light. Likewise when the amino acid reacts with the ninhydrin, it reacts in resulting into the pink colour. And when the oils and fats are deposited in the residue, it results in reducing osmium tetra oxide to osmium, which resulted in formation of the black colour.

There is one more technique called the fuming technique. One of it is the Iodine fuming, where the fingerprints develop on most of the surfaces, but the process is more tedious and less satisfactory. It is used in those cases where the powdered methods don’t amount to satisfaction. There is no chemical reaction but there is absorption of the iodine resulting into the formation of the outline of the ridges. Second, cyanoacrylate fuming is the effective chemical to develop print on the skin, plastic and other surfaces where the powder can be used as the area is very sticky. These techniques of fuming are mostly used to develop and identify a rapist, whose fingerprints are found on pillion cover, or in the cases of the drug peddler. Third, the metallic vapour fuming is a method when there are patent and plastic fingerprint. In these the metals used are gold, zinc and metal alloys. They are evaporated in heated chamber in vacuum, and then vacuum gets deposited on the exhibit causing the formation of the fingerprint.

Then there is the laser development through which the fingerprint is traced. The use of laser in the location and collection of the latent fingerprints have given dramatic results because the fingerprints fluoresce when there is the laser technique is produced. The advantages of the laser technique are that the old print can be developed and there is no need of pre- treatment required. The print that is found on the surface is not sustained, soiled, damaged or affected in any way.

The fingerprint can be collected in various ways. The collection of the fingerprint varies depending upon the nature, surface or the place where it is found mostly. The article is one way to collect the evidence. Mutilation of the prints or breakage of the articles should be prevented by proper and careful packing. Another way is the photography. The photo of the fingerprint is very helpful as it will be impossible for the judge or any other body which is involved in the trial to go on every scene to see the fingerprint. In the case of Sonvir v. State of Delhi (CRIMINAL APPEAL NO. 958 OF 2017), the fingerprints were present in the crime scene and for the same, photography has done. Therefore, the fingerprint were matched which was traced through photography itself and these fingerprints were acted has only reliable evidence of prosecution.

Shreya

Symbiosis Law School

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