Fingerprint

Dactylography

• Study of fingerprints in which impressions of the papillary ridges and furrows of the fingertips are taken.

Its considered to be the surest sign of identification because:

• The pattern, distribution, arrangement and character of the ridges are absolutely individualistic and are present from birth and remain unaltered throughout life.

Introduction

• The system of Dactylography to identify individuals was first started in India
• The first ever Finger Print Bureau of the world was established at Writer’s Building at Calcutta in the year 1897

Caused by:

• Caused by raised portions of the skin on your fingers, toes, feet, palms and lips
• Raised portions are arranged in connected units call dermal, or friction, ridges
• When these ridges press against things, they leave a mark = Fingerprints.
• The imprint of a fingerprint consists of natural secretions of the sweat glands that are present in the friction ridge of the skin.
• Secretions made  up of
• Water
• Oil
• Salts
• Dirt, etc

FINGERPRINTS FORMATION

• Fingerprint patterns are probably formed at the beginning of the 10th week of pregnancy
• When the foetus is ~8cm long
• The basal layer of skin (a special layer within the epidermis where new skin cells are produced) grows faster than the skin layers above and below it, resulting in it collapsing and folding in different directions, creating intricate shapes between the other skin layers
• Fingerprint patterns cannot be altered or destroyed permanently by skin injuries, because it is protected by the outer layers.

CHARACTERISTICS OF FINGERPRINTS.

• Fingerprint characteristics are named for their general visual appearance and patterns.

1. Loop- 65%
2. Whorl- 25%
3. Arch- 7%
4. Composite- 2-3%

Loops

• ~65% of population have loops.
• Loops enter from either the right or left and exit from the same side that they enter

Whorls

• ~30% of population have whorls.
• Whorls look like a bull’s eye, with two deltas (triangles

Arches

• ~5% of population have whorls.
• Arches have ridges that enter from one side of the fingerprint and leave from the other side, with a rise in the centre

Forensic examiners also look for

• The presence of a core and deltas.
• The core is the centre of a loop or whorl.
• A delta is a triangular region located near a loop.
• Ridge count
• Core Ridge count area Delta

Basic fingerprint patterns can be further divided

• Plain whorl v central pocket loop whorl v double loop whorl v accidental whorl.
• Plain arch v tented arch

• Every individual has a unique fingerprint.
• Even identical Twins
• For positive identification at least 16 points should be similar. 

TYPES OF FINGERPRINTS.

Three types of fingerprints.

• Patent fingerprints
  • Visible prints left on smooth surfaces when blood, ink, etc. comes in contact with the hands and is then transferred to that surface.
• Plastic fingerprints.
  • Indentations left in soft materials such as clay, putty or wax
• Latent/Hidden fingerprints
  • Caused by the transfer of oils and other body secretions onto a surface.

Permanent  impairment of the fingerprint pattern occurs in

• Leprosy
• Electric injury
• After exposure to radiation

Also know:

• Ridge alteration occurs in eczema, acanthosis nigricans, scleroderma, and dry or atrophic skin. 
• In infantile paralysis, rickets and acromegaly, though the pattern is not altered, the distance between the ridges can be changed. 
• In most cases of coeliac disease, there is moderate epidermal ridge atrophy and even loss of pattern. 
• Incomplete atrophy of ridges is usually seen in dermatitis.

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