Fingerprints A Brief History

• Chinese: 3000 yrs. Ago, Chinese used fingerprints to sign legal documents

• Henry Fauld (1890): Suggested finger ridges could be used to identify criminals.

• William Herschel (1870): English civil servant in India; required natives of India to sign contracts with the imprint of their right hand.

• Alphonse Bertillon: Anthropometry-no two people have the same 11 measurements. Used 11 body measurements to identify individuals. Included height reach, width of hand, length of left foot, etc…

• Francis Galton: Published the book “Fingerprints.” Described 3 main fingerprint patterns; arches, loops, and whorls.

• United States: Henry System (1899)-Developed a fingerprinting system used by the FBI to date. First used by the NYC Civil Service Commission. FBI currently has the largest collection of fingerprints in the world.

• United States vs.Byron C. Mitchell (1999): A defendant’s attorney argued that fingerprints could not be proven unique. Judge upheld, said fingerprints were unique and could be admissible in court.

• Human skin is the first line of defense.

• 2 layers--epidermal and dermal • Papillae- Boundary between the 2 layers, that contain the ridge patterns.

• Sweat glands secrete oil that leaves an identification residue conforming the ridge pattern.

sweat pores

Sweat gland

Epidermal

Papillae

Dermis

Fingerprint Anatomy

Fundamental Principles of Fingerprints

• 1-A fingerprint is an individual characteristic; no two fingers have yet to possess identical ridge characteristics.

• Individuality of a fingerprint is not determined by the general shape, but by the

• examination of ridge characteristics (minutiae)

• Type, number, and location of ridge characteristics -Fingerprints have 150 different characteristics. -match 8-16 for an identification.

Fundamental Principles of Fingerprints

• 2- A fingerprint will remain unchanged during an individual’s

lifetime.

-Fingerprints form in the 17th week of gestation

-Twins do not have matching fingerprints.

-If a person tries to change the print:

1- 1-2 mm below the surface

2- Leaving scars

Fundamental Principles of Fingerprints

• 3- Fingerprints have general ridge patterns that permit them to be systematically classified.

- All prints can be classified as a loop, whorl, or arch

-Print:

Core (center), Deltas-form triangles on the side of the print

65% of all fingerprints in the world are loops.

Fundamental Principles of Fingerprinting Cont.

Loop

A loop must have one or more ridge lines entering from one side of the print, recurving, and exiting from the same side.

Fundamental Principles of Fingerprinting Cont.

• 30% of the population have whorls

• Must have two deltas

• Resembles a Bull’s eye or target

Fundamental Principles of Fingerprinting Cont.

Arch 5% of the population have arches

The ridge lines enter from one side of the print and exit from

the opposite side.

Fingerprint Classification

• Several steps

• Used as the first step in a crime scene

• Must identify the presence of a whorl

• Assign a numerical value based on the finger it (whorl) was found on

• Used to search databases

Example: Right index and right middle fingers are whorls and all the others are loops.

Automated Fingerprint Identification Systems AFIS

• Uses automatic scanning devices that convert the image of a fingerprint into digital image characteristics that contain data showing ridges at their points of termination or splits in the ridge.

• 40,000 new prints everyday

• Identifies 8,000 fugitives a month

• Looks at 67 years in 20 mins.

Methods of Detecting Fingerprints

• Visible Prints

• Occur when a finger has been placed in a colored substance like blood, paint, ink, mud, etc.

• Plastic Prints

• Prints that are made in soft substances like wax, soap, plastic

• 3D model of print

Non-Porous Surfaces

• Hard, smooth, nonabsorbent, glass, mirror, painted wall

Latent Prints “lie hidden”

Prints appear invisible, can be developed to be

seen.

Porous Surfaces Soft, absorbent materials Cloth, ceramic, concrete

Common Techniques Used

1. Dusting with Carbon Powder on white or light colored surfaces.

Color contrast

Dust gets stuck in oil of print

Use tape to lift print

2. Dusting with Lanconide Powder for black surfaces.

White powder

Gives color contrast

3. Dusting with Aluminum Powder for hard or dark colored surfaces as well as mirrors and metal surfaces. Color contrast Magnetic

4. Use of Cyancacrylate (Super-Glue) fuming Fumes polymerize and harden in the oils of the print Must dust the print afterwards

Methods of Detecting Fingerprints Cont.

• 5. Use of Iodine Fuming techniques -Iodine crystals sublime (5-7g)--goes from solid to gas at room temperature. -Gas sticks to print-not permanent--need to take pictures 6. Use of ninhydrin -Reacts with the protein in the print -Often used on porous surfaces 7. Use of Silver Nitrate -Reacts with sodium chloride (salt) in the oil. 8. Use of Gentian Violet -Fluoresce the print--print will glow 9. Use of Laser Technology -Using dyes and wave lengths of light, you can get the print to glow.

Preservation of Prints -Prints are often lifted with tape and them placed on a card -Contrasting background -Photograph is taken

Digital Imaging -Picture id transferred to a digital image. -Once the image is stored, it can be manipulated for better resolution. -Used to compare prints side by side -Only good as image produced