The palmer surface of the hand has a corrugated skin which helps in the firmer grip and friction. The elevated part is called as ‘ridges’ and the part between two elevated ridges (depression) is called as ‘furrows’.
Fingerprint is a reproduction on a smooth surface of the pattern or design formed by the ridges of the first joints of the phalange of the fingers. The scientific study of the fingerprints is called as ‘Dactyloscopy’.
Principles of Fingerprints
The fingerprint science is based on three fundamental principles which are as follows:
- Variety: No two finger prints are identical unless they are made by the same finger of the same person.
- Immutability: The finger prints will never change by any accidental injuries, ailments or any other physical changes of a person.
- Persistence: Finger print will persist throughout life of any individual and even after death until decomposition sets in.
Sir Francis Galton has described 3 patterns for classification of fingerprints: Arches, Loops and Whorls.
Edward Henry modified Galton’s system and described 4 basic patterns for classifications which are used normally are as follows:
Ridges flow from one side to other without making any curve. Pattern is made up of ridges lying one above the other in general arching formation.
Ridges flow from one side to other forming a tent in middle.
Ridges enter and exit in same side of the pattern making a recurve at the centre. The Loop has one delta and one core and at least one ridge between core and delta.
Loops are two types
- Radial Loop b)Ulnar Loop
In radial loops the slop of the ridges slant towards the radial bone i.e. the bone at the thumb side. The ridges slant towards the left in case of right hand fingers and of the right in case of left hand fingers.
In Ulnar loops the slop of th ridges slant towards the ulna bone i.e. the bone at the little finger side. The ridges slant towards right in case of right hand fingers and of the left in case of left hand fingers.
The whorl pattern consists of one or more ridges must recurve and make a complete circuit around the core, and there are two deltas ordinarily. Whorls may be circular, spiral or oval.
The composite pattern is composed of two or more different patterns, separate and part exclusive of the arch.
- Twinned Loop:
In the twin loop pattern, the recurving ridges present two loops formation separate and apart. There are two points of delta .The flows originate from the same side of the pattern.
- Central Pocket Loop:
The central pocket loop pattern consists of one or more free curving ridges and two points of delta. When the line of fingerprint disc is placed on the two points of delta, it will fail to intersect any of the ridges belonging to the core group.
- Lateral pocket Loop:
In the lateral pocket loop pattern, the recurving ridges present two loop formations, separate and apart without divided by either delta. There are two points of delta. The flow for the delta originates from the same side of the pattern.
- Accidental :
The accidental pattern will contain two points of delta. One delta will be related to a recurve and other will be related to up thrust.
How to take Finger prints?
- Printer’s Ink
- Rubber Roller
- Glass Slab
- Cleansing Rag
- Devise for holding finger prints slip
Please take a note that fountain pen ink and stamp pad ink both are not recommended as it dries quickly and runs into furrows.
- Slab and roller must be clean and free from dust.
- Printer’s ink should be used in small amount and in case of excessive ink, it should be removed.
- Excessive pressure should be avoided.
- No rolling on the same part until it is re-rolled with ink.
- While taking prints thumbs should be rolled towards body and fingers away from subject’s body.
Taking fingerprints of Dead Bodies
The fingerprints of the deceased are taken when the identity is not confirmed under normal investigation like any person killed in an accident, suspicious death or while committing any kind of crime, etc.
Those who have died presently and rigor mortis has not taken place, the process of taking fingerprints is simple since fingers are flexible. If in case the fingers are not flexible, little massage will make them, flexible and thus prints can be obtained.
In case where the rigor mortis has set in, the prints can be taken by applying ink to the fingers with the help of rubber roller and then fix a square paper on the broad side of the wooden pad and roll it from side to side of the fingers. The prints of the fingers can then be pasted on a fingerprint slip in a sequence format.
In case where decomposition has set in, the fingers are treated with dilute solution of sodium hydroxide, thus the crimpled and dried skin regains its normal shape due to swelling by absorption of solution.
In case if the body has reached the advance stage of decomposition than glycerine or hot water are injected in the finger through fine needle until the finger reaches its original shape and size.
When the skin tissue is worsening by decomposition, X-ray photography is useful.
If proper facilities are not available at the place where the dead body is recovered, the epidermal skin (outer layer) of the skin should be removed carefully, preserve it in 10 different bottles containing suitable preservatives and then record it.
Reasons for taking Fingerprints
Fingerprints are taken for following reasons:
- To have record of the individuals who are convicted in the court of law.
- To establish identity, check on for criminal history of any suspect or perpetrator of the crime.
- To establish identity of the individuals in mass disaster, or of mutilated bodies.
- For comparison between chance prints found at the crime scene and rolled prints taken from a suspect.
- For comparison in questioned documents.
The identification of the individual is not on the basis the pattern of fingerprints but on the basis of the ridge characteristics; i.e. Presence of ridge characteristics occurring in their same nature and relative position, in the disputed impression and specimen impression.