Forensic Science

Objectives◦ Discuss the history of

fingerprinting◦ Discuss the characteristics of

fingerprinting◦ Identify the basic types of

fingerprinting◦ Describe how criminals attempt

to alter their fingerprints◦ Determine the reliability of

fingerprints as a means of identification

◦ Explain how fingerprint evidence is collected

◦ Describe the latest identification technologies

◦ Determine if a fingerprint matches a fingerprint on record

◦ Use a process of lifting a latent print

Vocabulary◦ Arch◦ Core◦ Delta◦ Fingerprint◦ Latent fingerprint◦ Loop◦ Minutiae◦ Patent fingerprint◦ Plastic fingerprint◦ Ridge pattern◦ Ten card◦ whorl

Fingerprints as a means to identify individuals was a major breakthrough in forensic science

The objective of this activity is to produce a fully printed ten card, identify your fingerprints, and compare your fingerprints to those of your classmates

Loop

New tool to solve crimes, clear the innocent, and convict the guilty

Interesting fact – Identical twins have the same DNA, but has a unique fingerprint made up of whorls, loops, or arches.

Oldest known document showing fingerprints dates back to third century B.C.

Earliest known record of the study of patterns on human hands was 1684 by Dr. Nehemiah

In 1788, Johann Christoph Andreas Mayer explained how the ridges were never duplicated in two persons

In 1823, Jan Evangelist Purkyn described nine distinct fingerprint patterns

In 1879, Alphonse Bertillon used fingerprints to identify criminals and was used in 1883 to identify a repeating offender.

In 1902 he solved the first murder using fingerprints.

1888, Sir Francis Galton (who verified prints do not change with age) and Sir E.R. Henry developed a classification system for fingerprints that is still in use today

1891, Ivan Vucetich improved fingerprint collection. Noted measurements and took all ten fingerprint impressions

1896, Sir Edmund Richard Henry grouped fingerprints based on whether they had an arch, whorl, or loop pattern.

Each fingerprint card was imprinted with 10 fingerprints of a person and marked with individual characteristics, ten card.

All fingers, toes, feet, and palms are covered in small ridges, called dermal, or friction ridges

Can leave an impression called a fingerprint

The imprint of a fingerprint consists of natural secretions of sweat glands◦ Water◦ Oils◦ Salts◦ Everyday dirt

Skin is divided into three layers: Surface is called epidermis

◦ Thin layer (skin is shed)◦ Mostly waterproof◦ provides protection from bacteria

and viruses◦ Contains melanin that filters UV

rays from the sun The second layer is called the

dermis◦ Provides strength and flexibility◦ Contains nerve endings and,

sweat glands, oil glands, hair follicles, and blood vessels

The subcutaneous layer is the most internal layer of the skin◦ Provides insulation◦ Offers protective padding◦ Stores energy

Latest information suggests patterns are probably formed at the beginning of the 10th week of pregnancy

Occurs at the basal layer within the epidermis

Occurs because the basal layer grows faster than the epidermis and the dermis the layer collapses and folds in different patterns

Named for their visual appearance◦ Loops - 65%◦ Whorls - 30%◦ Arches - 5%

Two things a forensic investigator looks for:◦ Core – is the center of a

loop or a whorl◦ Delta – a triangular

region located near a loop

Investigators also look at ridge count.

The basic fingerprint patterns can be further divided.

Whorl patterns:◦ Plain whorl (24 %) ◦ Central pocket loop whorl (2 %)◦ Double loop whorl (4 %)◦ Accidental whorl (0.01 %)

Arch patterns:◦ Plain arch (4%)◦ Tented arch (1%)

Central Pocket Loop Whorl

Tented Arch

Double Loop Whorl

Plain Whorl

Arch

Accidental Whorl

In order to positively match a print, more information is needed.

Every individual has a unique fingerprint resulting from unique ridge patterns called minutiae.

Recognizing those details in the differences between ridges, their relative number, and their location on a specific fingerprint is called fingerprint identification.

In order to match fingerprints, a minimum number of points of comparison are needed.

Patent fingerprints◦ Visible prints, are left on a smooth surface when blood,

ink, or some other liquid comes into contact with the hands and is transferred to the surface.

Plastic fingerprints◦ Actual indentations left in some soft material such as

clay, putty, or wax. Latent fingerprints

◦ Hidden prints, are caused by transfer of oils and other body secretions onto a surface. They are made visible by dusting with powders or making the fingerprints more visible using a chemical reaction

Criminals tried to devise ways to alter their fingerprints

Ex. 1930’s, John Dillinger tried to remove his fingerprints with acid->Fingerprints came back!

Many experts claim fingerprint identification is flawless

However, humans input and analyze data, and humans make mistakes

Results need to be checked and double checked to prevent false convictions

One study showed that 1 in 5 investigators make a false identification.

By 1987, the FBI had 23 million criminal fingerprint cards on file

Had to manually search, could take up to three months to find a match

In 1999, the FBI develop the Integrated Automated Fingerprint Identification System (IAFIS or AFIS)

Operates 24 hrs a day, 365 days a year, now takes up to two hours

47 million people are recorded in the data base

Dusting (drinking glasses, faucets, telephones, etc) with a fine carbon powder can make a fingerprint more visible.

Tape is used to lift and preserve it Also take photo of the print Metal or magnetic powders can also be used Chemicals can also be used to make latent prints

visible◦ Ninhydrin◦ Cyanoacrylate vapor (superglue)◦ Silver nitrate◦ Iodine fuming

Chemical Uses Application Safety Chemical Reaction Latent Print

Ninhydrin Paper Object Dipped or sprayed and wait 24 hours

Do not inhale or get on your skin

Reacts with amino acids (proteins) found in sweat

Purple-blue print

Cyanoacrylate Vapor

Household items: plastic, metal, glass, and skin

Heat sample in a vapor tent.

Do not inhale or get on your skin; affects mucus membranes

Reacts with amino acids

White print

Silver Nitrate Wood ,Styrofoam Object dipped or sprayed in silver nitrate

Wear gloves to avoid contact with the skin

Chloride from salt in perspiration on the print combines with silver nitrate form silver chloride

Black or red dish brown print under UV Light

Iodine Fuming Paper ,Cardboard & Unpainted surfaces

In a vapor tent, heat solid iodine crystals

Toxic to inhale or ingest

Iodine combines with carbohydrates in latent print

Brownish print (fades quickly)—Need to photograph

New scanning technology and digital system, fingerprints can be scanned at the rate of 500 to 1,000 dots per inch

Start investigating trace evidence picked up and left behind by our fingerprints (ex. explosives, cigarettes, drugs)

Biometrics is the study of using physical traits to identify people.