chapter 7 anatomical evidence: the outside story

Chapter 7 Anatomical Evidence:

The Outside Story Prof. J. S. Dodd

The Outside Story For more than well over 2,000 years, people have looked to the bodies of suspects and victims to reveal the sequence of actions that occurred as part of the commission of a crime.

Today, we can find the information from our bodies that can ideally provide a unique and unambiguous identification of a person for both forensic and security applications alike.

Thus, if we know where and how to look for it, Locard's Principle tells us that we should be able to find important evidence left behind by our physical bodies themselves.

The Outside Story The types of evidence that we’ll consider in this chapter also typically fall within a broad definition of evidence called trace evidence. • Fingerprints • Hair • Fiber • Glass • Soil • Explosives

One definition of trace analysis involves the comparison of small pieces of evidence with a standard (often called an exemplar) in an attempt to see if the origin or use of the evidence can be identified.

Learning Goals and Objectives

•  Forensic medicine and anatomical evidence can provide critical forensic information. In order to have a deeper appreciation of how external anatomical structures provide essential forensic information


•  What makes up our skin and how does it function

•  What are ridge patterns in skin •  How can ridge patterns can be

transferred and detected as fingerprints •  How fingerprints can be compared and

what information they contain •  What is the chemical and physical

structure of hair and fibers


•  How can hair and fibers be identified •  What is biometrics and how can biometric

information be used •  What are the limitations and strengths of

biometric information.

Forensic Fingerprints

Fingerprints have been used for centuries as a unique mark of a particular person. We now recognize that each person has a set of ridges on their fingers that sets them apart from all others and, therefore, allows their fingerprints to be used to potentially identify their involvement is crimes. In order to understand how fingerprints are used, you will need to develop an understanding of: • the origins and development of fingerprints as unique personal identifiers • the biological formation of “friction” ridges and their structures and features • the main patterns of fingerprints: loops, whorls and arches • the identification and use of minutiae and other fine features for identification;

As the chapter progresses, you will also need to develop an understanding of: • the meaning of visible, latent and plastic fingerprints; • the methods for visualizing, lifting, preserving, and comparing latent fingerprints; • the development of IAFIS and similar systems; • The use of other biological structures for identification (e.g., lips, ears, skin)

Fingerprints – A little history • 1000 BCE; archaeological evidence of ancient Chinese and Babylonian

civilizations using fingerprints to sign legal documents. •  1823 - Prof. John Evangelist Purkinje of the University of Breslau, published a

thesis on different types of fingerprint patterns • 1858 - Sir William Hershel, Chief Administrative Officer in Bengal, India, saw

the clear advantages of using fingerprints to identify repeat criminals and advocated fingerprint use in the personal identification records of prisoners.

• 1892 - After some years of research the English scientist Sir Francis Galton published a book entitled Finger Prints in which was laid out a method of classification of fingerprints.

• 1897 - Indian Police officer Sir Edward Henry, Principle of Persistency, as well as, proposed a modified classification system which was adopted by Scotland Yard in 1901 and is still the basis of the systems used in most English speaking countries.

• 1901 - First official use of fingerprints in the USA by the New York City Civil Service Commission.

• 1930 National fingerprint file set up in America by the FBI ! 1977’ AFIS… Later to be changed to IAFIS – 99’

Fingerprints •  Fingerprints form from contact of friction ridges on hands,

feet, or lips with an object (called 'friction' ridges because of their biological function to assist in our ability to grasp and hold onto objects - approximately 2,700 ridge "units" per square inch of friction skin).

•  Pore openings are present along the surface of the friction ridges.

•  Fingerprints are formed underneath the skin in the dermal papilae. As long as that layer of papilae is there, fingerprints will always come back, even after scarring or burning.

•  Prints are left on a surface because a body is constantly secreting water, oils and other compounds through pores.

What is the Ridge?

What is a furrow?

Forensic Fingerprints • Your fingerprint patterns are hereditary. • They are formed before a person is born,

while still in the womb, never change through out a lifetime.

• They are totally unique, and they never change.

• Gloves don't necessarily stop fingerprints. Prints can be left through surgical gloves. Gloves can also be turned inside out to yield fingerprints from the inside surfaces. Leather gloves can be treated in the same manner (leather leaves a print that is unique to that glove and no other - leather comes from cow skin, which is just as random as human skin). Even cloth gloves, such as mittens, can leave a distinctive print that can be traced back to the mitten that made it.

Latent Leather Glove Print

Ref. Leather Glove Print

Fingerprint Basics •  A fingerprint is an individual characteristic.

–  It is not the shape of the print that is individual, but rather the number, location and shape of specific ridge characteristics (also known as minutiae).

–  Most courts require 14-16 matched minutiae for a positive match.

•  A fingerprint will remain unchanged during an individual's lifetime. –  A known exception is due to the use of Capecitabine

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

Arches

•  Plain Arch –  No significant core –  Lines come in from one

side and exit other side without much change in pattern

Arches

•  Tented Arch –  Line type quickly rises

and falls at steep angle

Arches

•  There are no deltas •  Compose 5% of population •  Two types

– Tented 1% – Plain 4%

Loops

•  Compose 60% of population •  There is one deltas •  Two types

– Ulnar – Radial

Loops / Deltas

Loops:1 or more ridges entering from the side of the print, recurving and exiting from the same side. Although named after the bones, if it opens toward little finger its ulnar and toward thumb it’s radial.

Deltas: A place where two lines run side by side and then diverge with a significant recurving line which passes in front of the delta " A triangle is formed

Loops / Deltas

Loops: core of loop is approximately the center; see blue box

Deltas: see red box

The point of ridge divergence where the upward and downward deflected ridges meet the looping ridges (the rock in the stream) forms a delta (a small triangular region). Often, a small island is also observed at the center of the delta.

Ridge Count

Ridge Count: If a line is draw from the top of the core to the delta point, it intersects a number of ridges between these two features. The number of ridges between these two features is known as the ridge count.

Whorls

•  Compose 30% of population •  There are two deltas •  Several types

– Plain – Central Pocket – Accidental – Double Loop

Whorls

•  Plain Whorl –  Consists of one or more

ridges which tend to make a complete circuit

–  If a line is drawn between the two deltas, it must intersect at least one recurving ridge within the inner pattern

Ok, now to make things confusing

This is a central pocket loop whorl

What do you think this is?

Why?

Whorls •  Central Pocket Whorl

–  DOES NOT consist of a ridge that makes a complete circuit

–  If a line is drawn between the two deltas, it does not intersect a recurving ridge within the inner pattern

Whorls •  Double Loop Whorl

–  Consists of two distinct, separate, loop formations

–  Has two deltas •  Loops have separate and

distinct shoulders

•  What do you see?

What do you see?

Identify each fingerprint pattern.

Right Hand

Left Hand

Left Hand

Right Hand

Right Hand

Minutiae Points

Minutiae Points

•  Common micro features in a fingerprint –  Intersection of bifurcation –  Ending points of islands –  Center points of sweat glands

•  There are about 30 different types of minutiae points –  No two people have the same number

in the same places on their fingertips –  This is where real differences add up

Can be:

Identification Points

There is no magic number of points needed for an identification

Crime Scene Fingerprints

•  Fingerprints found at crime scene are often incomplete or less than perfect

•  An inked (known) print is compared to a latent (unknown) print

•  Ridge characteristics must be of the same shape and type, occupying the same relative position –  Must be an adequate # of

indistinguishable features with no unexplainable differences

Types of Crime Scene Prints

•  Visible –  Made after the ridges have been in contact

with a colored material\ •  Blood, paint, grease, ink

•  Plastic –  Ridge impressions left on soft material

•  Putty, wax, soap, dust

•  Invisible (latent) –  Transfer of body oils to the surface of an

object

Visible Prints

•  Print left behind due to a transfer of a visible source – Examples:

Plastic Prints

•  Print left behind due to it being pressed into a surface – Examples:

Inked / Latent Print Comparison

•  Print left behind that must be made visible before it can be collected into evidence – Examples:

Development Procedures

•  Hard, nonabsorbant surfaces – Glass, tile, mirrors, painted wood

•  Application of powder

•  Soft, porous surfaces – Paper, cardboard, cloth

•  Chemical visualization

Powders •  Fingerprint powder, a brush, and some

tape be enough to visualize about 70% of the fingerprinting that is ordinarily done at the crime scene

•  Powders react with the oils left by a person who handles a particular object

•  The amount of time these oils will stay on an object depends on the surface that the print is left on as well as the surrounding environment

Latent Prints Activity

•  Using your picture frame, lets lift your fingerprints

Chemical Processing

•  Latent prints are made visible by applying a substance that causes a chemical reaction with one of the components of latent prints

Iodine Fuming

•  Iodine is a substance that sublimes to produce a vapor of iodine

•  Iodine reacts with the oils on fingerprints

•  The print is stained brown –  Visualization fades quite quickly

•  Stored as a photograph

Ninhydrin Procedure

•  Ninhydrin powder is mixed with solvent like alcohol and sprayed onto the object surface

•  Reacts with the amino acids in the latent prints

•  Forms a deeply violet colored visible prints

Ninhydrin Reaction

Super-glue Fuming

•  Heat is applied to a small amount of super glue in a closed environment containing the evidence –  Heating causes the super glue to turn into

vapors •  Super glue vapors settle on the

evidence and reacts with the latent print –  A visible, white outline of the print is

formed

Silver Nitrate •  Silver Nitrate dissolved in water or alcohol is

sprayed on the object surface •  Reacts with the chlorine found in the salt in

perspiration –  Renders the print inert to other chemical processes

by creating an insoluble solid (AgCl) •  Two step process

–  Spraying or dipping the object in silver nitrate –  Developing the print with sunlight or a carbon vapor

light •  Permanently stains object

Photography •  Ultraviolet Digital Camera

for fingerprint collection D5UV is a high-performance and portable ultraviolet digital camera system for fingerprint collection. You can view and search fingerprints from the LCD screen of the D5UV. You can focalize quickly and accurately and get high quality images.

IAFIS

•  Integrated Automated Fingerprint Identification System

•  Computerized systems which allow fingerprints to be compared to fingerprints in a database

NGI •  Next Generation Identification System

–  Includes fingerprints, eye-scans, facial imaging methods

–  Faster identification possible

What about the identity of the deceased?

•  "The fingerprinting of a decomposed corpse sometimes requires the medical examiner to remove the deceased’s fingertips and slip them over their own gloved fingertips, which then allows them to take the prints."

PBS Fingerprint Conclusion

•  http://www.pbs.org/wgbh/pages/frontline/real-csi/

Alternative Epidermal Friction Ridges

•  Palm •  Footprint •  Lip •  Ear

Fingerprint Unit Vocabulary Arch- a fingerprint pattern in which the ridge pattern originates from one side of the print and leaves from the other side.

Core- a center of a loop or whorl

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

Fingerprint- an impression left on any surface that consists of patterns made by the ridges on a finger.

Latent Fingerprint- a hidden fingerprint made visible through the use of powders or other techniques.

Loop- a fingerprint pattern in which the ridge pattern flows inward and returns in the direction of the origin.

Minutiae- the combination of details in the shapes and positions of ridges in fingerprints that made each unique; also called ridge characteristics.

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

Plastic Fingerprint- a three-dimensional (3-D) fingerprint made in soft material such as clay, soap, or putty.

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 three categories: arches, loops, and whorls.

Ten Card- a form used to record and preserve a person’s fingerprints.

Whorl- a fingerprint pattern that resembles a bull’s-eye

chapter 7 anatomical evidence: the outside story

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