Chapter 6 Forensics

Fingerprint

An impression left on any surface that consists of patterns made by the ridges on a finger

True or False: Fingerprints are considered to be a form of class evidence.

False

How do forensic examiners analyze fingerprints?

Examiners analyze fingerprints by sending to a machine called IAFIS which provided digital, automated fingerprint photo files, and electronic storage of fingerprint photo files, and electronic exchange of fingerprints and test results. When submitted investigators can expect their results within 2 hours.

True or False: The type of power used to dust prints will vary depending upon the weather conditions when the print is lifted.

False

True or False: Fingerprints are a result of oil secretions form skin mixing with dirt.

True

The three main types of fingerprints are classified as

loops, whorls, and arches

Fingerprints are formed

At 10 weeks' gestation (in the womb)

How are fingerprints formed? Why do we have them?

Fingerprints are probably formed at the beginning of the 10th week of pregnancy, when the fetus is about 3 inches long. The basel layer a special layer within the epidermis where new skin cells are produced. The basel layer grows faster than the epidermis on the outside and the dermis on the inside. The layer collapses and folds in different directions, creating intricate shapes between the other layers of skin. We have fingerprints so we can be identify and so that we can grip onto objects.

Know the fingerprint ridge minutiae patterns from the textbook (pg. 139)

Look in Book

Can fingerprints be permanently removed? Disguised? Defend your answer.

No, your fingerprints cannot be removed because your fingerprints always grow back the same. They can be disguised, for example workers who worked in the pineapple fields in Cuba did not have any fingerprints because several of the chemical substances found in the pineapple plants, combined with the pressure or handling the plants, dissolved their fingerprints. When they ended their contact with the pineapples, their fingerprints grew back.

Fingerprints that are actual indentations left in soft material such as clay or putty are referred to as

Plastic Fingerprints

Jan Purkyn

Published a thesis discussing a fingerprint patterns, 1823.

How are fingerprint minutiae helpful in matching an unknown fingerprint?

Recognizing these details in the differences between ridges, their relative number, and their location on a specific fingerprint is called fingerprint identification. When forensic examiners identify a fingerprint, they are in theory identifying the unique signature of a person, and they can be pretty sure they are characterizing one, and only one, particular individual in the world. To match fingerprints, a minimum number of points of comparison are needed.

Minutiae

The combination of details in the shapes and positions of ridges in fingerprints that make each unique; also called ridge characteristics

The use of fingerprints in identification is not perfect because

The current technology depends on humans to input and analyze the information, and humans make mistakes

How are latent fingerprints collected?

They can be made visible by during with powders or making the fingerprints in some way more visible by using a chemical reaction. Tape is used to lift and preserve the fingerprint.

Alphonse Bertillion

(a) 1879- Began to develop the first scientific system of personal identification called anthropometry (b) 1883- used his method to identify 241 multiple offenders (c) 1902- Responsible for the first criminal identification of fingerprint without a know suspect.

List, describe, and be able to identify the 3 types of fingerprint patterns.

1. Arches- 5% of people have. Have ridges that enter from one side of the fingerprint and leave from the other side with a rise in the center. 2. Whorls- 30% of people have. Look like bull's-eye, with 2 deltas (Triangles) 3. Loops- 65% of people enter from either the right or the left and exit from the same side they enter.

Another way to make prints visible is to apply certain chemicals. What aspect of a fingerprint chemically reacts with each of the following?

1. Ninhydrin reacts with sweat from the fingertips, the amino acids in the sweat cause this to react 2. Cyanoacrylate reacts with amino acids 3. Silver nitrate reaction caused silver chlorine when the salt from sweat left on the print combines with silver 4. Iodine fuming reacts when it is combined with carbohydrates in a latent print

Be able to name the 4 different chemicals used to collect latent fingerprints and the color associated with each.

1. Ninhydrin- turns print purple-blue and reacts with amino acids (proteins) found in sweat. 2. Cyanoacrylate- reacts with amino acids and turns print white, vapor. 3. Silver Nitrate- chloride from salt in perspiration on the print combines with silver nitrate to form silver chloride. 4. Iodine Fuming- Iodine combines with carbohydrates in latent print. Brownish print (fades quickly) must be photographed or sprayed with a solution of starch.

Name 3 different whorl patterns. (Really 4 of them)

1. Plain whorl- 24%, has one or more ridges that make a complete spiral. There are two deltas, and if a line is drawn between them, at least one ridge in the inner pattern is touched or cut by the line. 2. Central pocket loop whorl- 2%, has one or more ridges that make a complete circle. There are two deltas, and if a line is drawn between them, no ridges in the inner pattern are touched or cut by the line. 3. Double loop whorl- 4%, has two separate loop formations and two deltas. 4. Accidental whorl- 0.01%, has two or more deltas and is combination of two of the other patterns (but not a plain arch)

Core

A center of a loop or whorl

Loop

A fingerprint pattern in which the ridge pattern flows inward and returns in the direction of the origin

Arch

A fingerprint pattern in which the ridge pattern originates from one side of the print and leaves from the other side

Plastic Fingerprint

A three-dimensional fingerprint made in soft material such as clay, soap, or putty

Delta

A triangular ridge pattern with ridges that go in different directions above and below a triangle

Patent Fingerprint

A visible fingerprint that happens when fingers with blood, ink, or some other substance on them touch a surface and transfer that pattern of their fingerprint to that surface

How have technological advances contributed to fingerprinting?

Advances in technology has contributed to fingerprinting by coming up with new scanning technologies and digital systems of identifying patterns. Fingerprints can be scanned at the rate of 500 to 1,000 dots per inch. This provides an image that reveals mine pore patterns on the fingerprint ridges, allowing for even better pattern matching. Technologies currently being developed to use other physical features to identify people, including retinal patterns in the eyes, facial patterns, and the pattern of veins in the palm of the hand.

Juan Vucetich

Began the first fingerprint files based on Galton pattern type. Also made the first criminal fingerprint identification (1892), 1891.

Sir Edmund Richard Henry

Developed the classification system for fingerprints that is still in use today in the US and Europe. Created a system that divided fingerprint records into groups based on whether they have an arch, whorl, or loop pattern, 1896.

True or False: Fingerprints are formed deep within the dermis layer of the skin

False

True or False: It is necessary to obtain a full print from a suspect in order to match his fingerprint with a fingerprint found at the crime scene

False

True or False: Plastic prints must be dusted or treated in order to identify the ridge patterns

False

True or False:Fingerprints of the left hand are mirror images of the fingerprints on the right.

False

Describe how to take a ridge count from a fingerprint

Find a delta in the print and circle it and then find the core and circle it. Then draw a line connecting the core and the delta. Then count from the core to the delta and you got yourself a ridge count.

Dr. Nehemiah Gray

First European to publish friction ridge skin observations, 1684.

Johann Crisoph Andreas Mayer

First to recognize that each set of fingerprints is unique, 1788.

Know how to name the 2 different loop patterns (radial and ulnar loop).

Radial loop- loop which opens towards the thumb Ulnar loop- loop which opens towards the pinky

What is a ridge count? Why is it necessary? What 2 parts of a fingerprint are needed to do this?

Ridge count is an imaginary line is drawn from the center of the core to the edge of the delta. Ridge counts are necessary because you could have two fingerprints that look alike but could have 2 different ridge counts, which means most likely you have 2 different fingerprints. The 2 parts of the fingerprint that are needed are the delta and the core.

Sir William Herschel

The English first began using fingerprints with Herschel. Chief of Magistrate, first used fingerprints on native contracts, 1856.

True or False: Loops are the most common form of fingerprints

True

How reliable are fingerprints as a means of investigation?

Yes because it's a good way of identifying a person for a crime or murder. No because fingerprint examiners make mistake and can make false-positive identification. For example, the FBI arrested and jailed Oregon layer Brandon Mayfield based on fingerprint evidence that linked him to the Madrid train bombings in 2004, which killed 170 people. He was held in custody for 2 weeks, until the Spanish authorities told the FBI that the mark was, in fact, that of an Algerian citizen. Fingerprint examiners need to be held to a high standard of performance.

Know the difference between a tented and plain arch pattern.

Tented arch pattern- 1%, does form an angle, or it may possess some characteristic of the loop pattern, such as a delta. Plain arch patter- 4%, shows ridges entering one side, rising in the center, and flowing out the other side without making an angle.

Ridge Pattern

The recognizable pattern of the ridges found in the end joints of fingers that form lines on the surfaces of objects in a fingerprint. They fall into 3 categories: arches, loops, and whorls.

Whorl

A fingerprint pattern that resembles a bull's-eye

Ten Card

A form used to record and preserve a person's fingerprints

Latent Fingerprint

A hidden fingerprint made visible through the use of powders or other techniques

A small triangular region is one characteristic found in a fingerprint. This triangular region is known as a

Delta

True or False: Similar print or ridge patter can also be found on the toes

True

True or False: With the aid of IAFIS it is possible to obtain a match in several hours

True