Fingerprint Patterns & Minutiae

Big Men in Fingerprinting History Sir Francis Galton – performed the first serious study of fingerprinting and published Finger Print in 1892 Sir Edward Henry – developed classification system based on patterns of ridges. Still used in most English speaking countries today.

How are fingerprints formed? Only found on hairless parts of body Formed by papillary ridges by the fourth month of pregnancy

How are fingerprints formed? Sweat glands secrete sweat to skin surface Sweat necessary to form latent prints

Types of Fingerprints Latent – the most frequently found invisible to the eye formed by sweat, oil on surfaces of finger ridges must be treated with chemicals, powders, etc. to be visible

Types of Fingerprints Visible – easily seen by the unaided eye most common when fingers are blood stained can also be made by ink or other similar medium staining fingers of person leaving print rarely found at crime scenes since perpetrators would attempt to wipe away easily seen evidence of this type

Types of Fingerprints Plastic – a.k.a. molded print made by impression of fingerprint in soft material soft material might be drying paint, putty, soap and cheese (most often the bane of dairy thieves the world over!)

Fingerprint Principles Immutable – the patterns of ridges do not change over the course of a person’s life. The patterns begin to form on the skin surface during the third month of pregnancy. Unique – the patterns of ridges are specific to the person. Even identical twins have unique fingerprints.

Fingerprint Patterns - Arches Made up of ridges lying one above the other in a general arching formation Least common of the general patterns of fingerprints. Two types of arches: plain, like shown here

Fingerprint Patterns - Arches Tented arch Sharp upthrust of sides of arch results in an angle that is less than 90°

Fingerprint Patterns - Loops Consists of one or more free-recurving ridges and one delta Radial loop – loop comes from thumb side of hand Ulnar loop – loop comes from pinkie finger side of hand NOTE: Perpetrators rarely leave Post-it notes telling you which hand they used during a crime!

Loops Loops must have one delta and one or more ridges that enter and leave on the same side. These patterns are named for their positions related to the radius and ulna bones. Radial Loop (Right Thumb) Loop opens toward the left or the radial bone. Ulnar Loop (Right Thumb) Loop opens toward right or the ulna bone NOTE: On the left hand, a loop that opens to the left would be an ulnar loop, while one that opens to the right would be a radial loop.

Fingerprint Patterns - Whorls Whorls have at least one ridge that makes (or tends to make) a complete circuit. They also have at least two deltas. If a print has more than two deltas, it is most likely an accidental.

Fingerprint Patterns - Whorls Double loop pattern Two loop formations that are separate and apart 2 deltas

Fingerprint Patterns - Whorls Central pocket loop consists of one or more free recurving ridges and two points of delta “Lollipop” effect with one delta and its ridge lines

Fingerprint Patterns - Whorls Central pocket loop “Lollipop” effect with one delta and its ridge lines

Fingerprint Patterns - Whorls Accidental pattern –doesn’t fit into other category.

Fingerprint Patterns Describes the shapes that are produced by the black or colored portions of the fingerprint, NOT the white or uncolored portions The black portions are called ridges

Minutiae Patterns Whorls, Loops, & Arches are class evidence. A suspect could be excluded based on the type of print To individually identify, details of print must be examined. Minutiae Pattern: The shape, pattern, and position of a ridge pattern that make it unique. These usually places where the ridge changes.

Fingerprint Patterns Ridge ending – a ridge that ends abruptly

Fingerprint Patterns Bifurcation – a single ridge that divides into two ridges.

Fingerprint Patterns Lake or enclosure – a single ridge that bifurcates and reunites a short time after to form a single ridge

Fingerprint Patterns Short ridge, island or independent ridge – a ridge that starts, travels a short distance and then ends

Fingerprint Patterns Dot – an independent ridge with approximately equal length and width

Fingerprint Patterns Spur – a bifurcation with a short ridge branching off a longer ridge

Fingerprint Patterns Crossover or bridge – a short ridge that runs between two parallel ridges

Points of Identification The same minutiae are present The minutiae flow in the same direction The minutiae occupy the same relative positions to each other

Classification system based on the presence of whorl pattern in Henry Classification Classification system based on the presence of whorl pattern in the fingerprint. R. Index (16) R. Ring (8) L. Thumb (4) L. Middle (2) L. Little (1) R. Thumb R. Middle R. Little L. Index L. Ring Approximately 25% of the population falls into the 1/1 category