Identification of a criminal or some other person using finger prints is known as Dactylography. Dactylography comes from two Greek words, daktylos meaning finger and graphein meaning to write.
This method of identification is also called Dectyloscopy. Introduction of methods to record, lift and develop the prints under various conditions has led to the advancement in the Forensics sciences. Studying finger prints is a much reliable, infallible and absolute method of identification.
Finger prints have been a very effective method of developing identity of the individual since long. Fingerprints play a critical role in investigating criminals because the court law consider fingerprints as a conclusive evidence. It is considered as one of the most accurate method of identification of any person.
This method is the cheapest and works by using patterns found on the fingertips. Ridge pattern of two persons can never be same. Moreover, there is no change in an individual’s finger print throughout life. There are various methods of recording fingerprints. This can be done by using standard fingerprint card.
Fingerprints can also be recorded digitally in order to transmit them electronically to the fingerprint department for the purpose of comparison. Comparing fingerprints at the crime scene with the recorded fingerprints of suspected people has proved to be beneficial to establish the identity or presence of a person at the crime scene.
The assertion that people can be identified by their fingerprints is supported by the friction ridge identification philosophy. According to this, the friction ridge identification is made by the agreement of friction ridge formations which have sufficient uniqueness. Person’s identification is categorized into two types i.e. Complete and Partial identification.
Most of the time, the identification of a dead body becomes difficult. This difficulty especially occurs in case of intensely decomposed bodies or the bodies that are mutilated. Such cases require the partial identification done by forensic expert to be arrived at a certain conclusion. Edward Henry explained different fingerprint patterns.
He described the three basic patterns – arches, loops and whorls which were sub-divided into eight basic patterns afterwards. These patterns are used by the FBI these day. Fingerprints are classified into three categories by the analysts, depending upon the type of surface containing them and the extent of their visibility.
Fingerprints are in the form of three-dimensional plastic prints when found on soft surfaces like soap, wax, wet paint etc. and can either be visible or invisible prints on a hard surface. Visible prints are formed when blood, dirt, ink, paint, etc., is transferred from a finger or thumb to a surface. Latent prints are formed when the body’s natural oils and sweat on the skin are deposited onto another surface.
Latent prints can be found on a variety of surfaces; however, they are not readily visible and detection often requires the use of fingerprint powders, chemical reagents or alternate light sources. Generally speaking, the smoother and less porous a surface is, the greater the potential that any latent prints present can be found and developed.
Patent prints are collected using a fairly straightforward method: photography. These prints are photographed in high resolution with a forensic measurement scale in the image for reference. Investigators can improve the quality of the images by using low-angle or alternate light sources and/or certain chemicals or dyes during photography, but this is usually not necessary.
One of the most common methods for discovering and collecting latent fingerprints is by dusting a smooth or nonporous surface with fingerprint powder (black granular, aluminum flake, black magnetic, etc.). If any prints appear, they are photographed as mentioned above and then lifted from the surface with clear adhesive tape.
The lifting tape is then placed on a latent lift card to preserve the print. Alternate light source it is becoming more commonplace for investigators to examine any likely surfaces (doors, doorknobs, windows, railings, etc.) With an alternate light source. These are laser or LED devices that emit a particular wavelength, or spectrum, of light.
Some devices have different filters to provide a variety of spectra that can be photographed or further processed with powders or dye stains. For example, investigators may use a blue light with an orange filter to find latent prints on desks, chairs, computer equipment or other objects at the scene of a break-in.
Using a fluorescent dye stain and an orange alternate light source helps this latent print appear clearly so that it can be documented. Use of various alternate light sources may help enhance the appearance of a fingerprint.
Authors: Kalsoom Rani and Maryam from department of chemistry, Kinnaird college for women, Lahore