Uses of fingerprints in medicolegal work
Never two people not even identical twins have the same fingerprints is the main cause of many different usages of fingerprints discussed below.Fingerprint is an impression left on a surface by the pattern of fine curved ridges on the skin of fingertip.The ridges occur in four patterns:loops,arches,whorls and compounds.Compounds are combination of the other three ridges and are the commonest of all.
The important features of the ridges are:
- They remain constant for the life and cann't be altered except by the destruction of true skin.
- They are present from birth both on epidermis and dermis(skin layers).
- They form patterns that are absolutely individual.
Its accepted that the chances of two fingerprints matching sixteen ridges characteristics are infinitively small.In the world's crime records,no two identical fingerprints have been reported.While in the case of criminals,impressions of all the digits of both hands are taken and preserved by the Police for further identification.
Advantages of this system of taking fingerprints include as their applicability to person of all ages,fingerprints can often be obtained even from putrefied bodies.An absolute identification is possible by this method with no special training or expensive instruments' need.Importantly, the print can be transmitted from one place to another as a coded or digitalized message.
The development of computerized automated fingerprint identification system(AFIS) now permits rapid entry,comparison and identification within minutes.
The ridge impressions are due to moistening of the skin by sweat and sebum from the skin glands.At the scene of crime they are found on door knobs,furniture,weapons and various other articles unless the criminal has worn gloves.Fingers soiled with blood or grease also leave appropriate impressions.If the impressions are faint,the fingerprint expert can make them visible by special techniques, for instance by the use of dusting powder in case of dead body,if the fingerprints are dried up,the prints canbe taken after soaking the fingers in an alkaline solution for some time.If the skin has pealed off as a result of burns,putrefaction,or drowning the prints can still be recorded either from the dermis(second skin layer) or from the pealed off skin hardened by formalin.
The practical applications of this method include:
1)Recognition of chance impressions left at a scene of crime.
2)Identification of the weapon used for commiting suicide or homicide.
3)Identification of decomposing or mummified bodies of unknown persons.
4)Prevention of impersonation in some cases.
5)Identification of habitual criminals by keeping fingerprints safe in record.
6)As an extra precaution on cheques and other legal documents that may bear a fingerprint in addition to manual signature.
Ridges of fingers and hands are studded with minute pores that are the openings of sweat gland ducts situated below the epidermis.These pores are ermant and varvy in number,size,shape and arrangement for a given area in each individual.The method of identification by examining these pores is known as Poroscopy or Locard's method.This method is very useful when only a part of the fingerprint or a fragments print is available for examination and identification.