Pattern evidence identification and individualization

Facial recogni�on with familiar people is easy, but trying to
recognize someone based only on descrip�on is challenging.
Erik S. Lesser/Associated Press
Bullet stria�ons are dis�nct impressions that can be used to ma
tch
bullets to the gun they were fired from. What are some other
examples of stria�ons?
Alexandre Meneghini/Associated Press
Chapter 7
Pattern Evidence I: General Patterns and Fingerprints
Andy Carpenean/Laramie Boomerang/Associated Press
Learning Objec�ves
A�er reading this chapter, you should be able to do the followi
ng:
Describe pa�ern evidence that can be used for iden�fica�on, i
ndividualiza�on, and reconstruc�on.
Explain the collec�on and preserva�on of pa�ern evidence.
Explain how pa�ern evidence is analyzed.
Summarize the nature and history of fingerprints and their role i
n personal iden�fica�on.
Discuss how fingerprint evidence is collected and preserved.
Explain how fingerprints are analyzed.

Ch. 7 Introduc�on
In this and following chapters, we will discuss pa�ern evidence
. Many of the topics concern pa�erns for individualiza�on, incl
uding physical pa�erns, fingerprints, footprints, footwear and
�re impressions,
handwri�ng, firearms and tool mark iden�fica�on, bitemarks,
and bloodstain pa�erns. This chapter looks closely at physical p
a�erns (broken or torn objects) and fingerprints (a major catego
ry of
individualiza�on pa�ern).
Pa�ern evidence can be very important in an inves�ga�on, bec
ause it includes many types of evidence familiar to most people.
Some types of pa�erns can poten�ally be individualized—
that is, a�ributed to a
specific source. In this way, people can be associated with or di
ssociated from specific places, like scenes, or from other people
. Conclusions from pa�ern evidence comparisons are usually m
ore defini�ve than
those from trace or chemical evidence, and correspondingly mor
e useful to juries and judges. Pa�ern evidence is examined by t
he eye, for the most part. No complicated instruments, other tha
n the occasional
use of microscopes, are required. Some�mes, a pa�ern evidenc
e match can be obvious to anyone, such as in a physical pa�ern
match (jigsaw fit), making the evidence easier to present to a co
urt.
7.1 Classifica�on of Pa�ern Evidence
Pa�ern evidence can be classified into three overarching catego
ries: pa�erns for iden�fica�on, pa�erns for individualiza�on,
and pa�erns for reconstruc�on. This idea follows by analogy fr
om the three ac�vi�es
that can comprise the elements of a forensic inves�ga�on—
iden�fica�on, individualiza�on, and reconstruc�on—
that we discussed in Chapter 1. So, just as we can talk about ide

n�fica�on, individualiza�on, and
reconstruc�on as elements of a criminalis�cs inves�ga�on, so
in the same way we can talk about pa�ern evidence categories t
hat have these elements as their goals.
Iden�fica�on (or classifica�on) pa�erns, which are used to id
en�fy things in our everyday environment by general shape and
form, are applied in forensic work to hair comparisons (Chapter
5) and handwri�ng
(Chapter 8). The different individualiza�on pa�erns that are im
portant in forensic work are discussed in detail in this and the n
ext chapter. In later chapters, we briefly discuss some reconstru
c�on pa�erns,
including bloodstain pa�erns. Before specific types of physical
pa�erns are discussed, let’s go over each category of pa�ern ev
idence.
Pa�erns for Iden�fica�on
Pa�erns for iden�fica�on are used to iden�fy objects and peo
ple in our everyday life and experience. For instance, right now,
you might be si�ng
at a table. How do you know it’s a table? You might say: "I kno
w it’s a table just by looking at it." The reasoning behind your k
nowledge is that
your brain has a record of the pa�ern of a table, which you lear
ned when you were younger. This pa�ern has to do with the sha
pe and form of a
table: its four legs and flat top. There are varia�ons of tables in
the world, but on the basis of their general pa�ern, we classify
them all as "tables."
When you see this par�cular pa�ern, it matches up with the bra
in pa�ern that iden�fies it as a "table." This works the same wa
y for facial
recogni�on. You recognize people you know instantly—
even in a large crowd and even if you haven’t seen them in a lo

ng �me. But what if one of
your friends tries to describe someone new to you in enough det
ail for you to find this stranger in a crowded place, like an airpo
rt? No ma�er how
much detail is provided, you may not find him or her.
It is very difficult to enumerate the features and proper�es of a
person’s facial pa�ern that one person recognizes in enough det
ail to allow
someone else to do so. The human mind is very good at pa�ern
recogni�on, but it is not yet clear in a detailed way how it work
s. In forensic work,
the examina�ons that most closely resemble this type of pa�ern
are hair comparisons and handwri�ng comparisons. In compari
ng hairs or
handwri�ng samples, the examiner looks at specific features in
the known and the ques�oned sample. But the comparison is mo
re than just a
checklist of which features match. The examiner incorporates th
e sum of all these feature comparisons into an overall pa�ern co
mparison between
the ques�oned and known. It is a lot like the facial recogni�on
example. Recognizing someone’s face is more involved than a si
mple checklist of the
features that are compared. One of the important things that dis
�nguish handwri�ng and hair comparisons from the other evide
nce category
comparisons is intra‐individual variability, which means that th
ere is variability in the knowns themselves, and this must be tak
en into considera�on
in the comparison.
Pa�erns for Individualiza�on
Pa�erns for individualiza�on are characteris�c of evidence tha

t can be unique among the members of their class. This can be v
ery important associa�ve evidence in an inves�ga�on. We mig
ht be able to figure
out that a par�cular �re made a �re mark, or a par�cular piece
of footwear made an impression, or that broken pieces of a hea
dlight lens came from a specific car in a hit and run, which may
�e a suspect to
the scene of a crime. There are two major types of individualiza
�on pa�erns: physical match pa�erns and impressions.
Physical Matches
Physical match pa�erns are formed from the pieces of randomly
broken objects and are some�mes called jigsaw fit matches. Th
e pa�erns are like a picture puzzle. For instance, if a glass was
broken and there
weren’t too many pieces, it wouldn’t take long to figure out ho
w the pieces fit back together to form the original glass. Even if
some pieces were missing, it would be likely that at least a few
pieces would fit
together. Note that this works for solid objects that fracture in a
random fashion. In cases of solid objects, these physical match
es are also known as fracture matches.
Suppose that several pieces of a broken glass were found at a cr
ime scene. Later, a suspect was developed and police searched h
is apartment. In the cuff of a pair of pants, a piece of glass was
found. The lab
performed an analysis and physically matched the pants‐cuff pie
ce to the glass pieces from the scene. This evidence goes a long
way toward pu�ng the owner of these pants at the scene around
the �me the
glass was broken.
Think About It

In the previous example about the suspect and the piece of brok
en glass, are you convinced that this evidence places the suspect
at the scene around the �me the glass was broken? What if you
were an
expert witness and the suspect’s lawyer asked, "How do you kno
w glasses break randomly? Why couldn’t there have been anothe
r glass in my client’s kitchen that broke in a way that produced
the piece
the police found, and it just happened to fit the scene pieces?"
How would you answer the lawyer’s ques�on? How would you
prove that glass breaks randomly and show that this is really an
individualiza�on?
When the object that fractures is solid and breaks in a random f
ashion, the physical matching of the pieces is called direct, or s
ome�mes primary. If an object or item isn’t solid or fractures i
n a way that
doesn’t result in clean, smooth fracture surfaces—
such as pieces of cut or torn fabric or a snapped piece of wood
with ragged irregular ends—
the physical match is called indirect, or secondary. Experts can
work to try to fit these pieces back together, but even if the mat
ch looks right, there is uncertainty. It is much easier to imagine
a piece of similar cut or torn fabric "matching" an unknown by c
hance than it is
in the broken glass case. Experts will not generally say that sec
ondary physical matches are true individualiza�ons. Instead, th
ey might say the pieces fit, and are consistent with having been
part of the same
original, but they cannot confirm a common origin.
Impressions
Another major type of individualiza�on pa�ern is impressions.
Impressions occur when two objects come in contact with one a
nother, and one

object leaves behind dis�nguishing markings on or in the other.
There are three types of impressions, which are dis�nguished b
ased on depth and
how the marks are made. Impressions that are essen�ally stamp
ed by an object into or onto another are called imprints if they a
re more or less
flat (two‐dimensional). They are called indenta�ons if they hav
e depth (three‐dimensional character). For example, many finger
prints and �re
impressions are imprints because they are le� on hard surfaces.
However, they can be indenta�ons if they are le� in a so� rece
iving medium, such
as a fingerprint in so� tar, or a �re impression in so� soil. If th
e receiving surface is marked by an object or surface moving ac
ross it—in effect,
being scratched by it—
the marks are called stria�ons. The markings on bullets that fire
arms examiners use to iden�fy the gun from which a bullet
came are stria�ons. Any sliding toolmark, like a mark made by
a screwdriver scraping across a latch plate on a door, is also a st
ria�on.
Pa�erns for Reconstruc�on
Pa�erns for reconstruc�on help create theories of the events th
at occurred at a scene. Reconstruc�on pa�erns include glass fra
ctures, furniture and
objects at a scene, tracks, trails, trajectories of projec�les, skid
marks in auto accidents, and more. Fracture pa�erns in glass ca
n help determine
what caused the breakage. The distribu�on and condi�on of clo
thing and objects at scenes can help to determine what happened
, if there was a
struggle, movements of persons involved, and so forth. Tracks a
nd trails can help show the direc�on of movement of people. Pr
ojec�le trajectories,

such as the path followed by a bullet in a shoo�ng case, can hel
p reconstruct the posi�on of the weapon with respect to the targ
et. Skid marks
help automobile accident reconstruc�onists determine the direc
�on and speed of vehicles just prior to an accident. Depending
on the speed and
direc�on of a vehicle at the �me its brakes are applied, a �re s
kid mark with a par�cular length and direc�on is created. Docu
menta�on and measurements of the marks can help reconstruct
direc�on and
speed. There are computer programs now that assist traffic acci
dent reconstruc�on specialists in these tasks.
Snow prints are among the most difficult
indenta�on markings to collect and
preserve. Can you think of any other
environments where pa�ern evidence
would be extra hard to recognize, collect,
and preserve?
Johner/SuperStock
Analysis of pa�ern evidence, such as this sneaker sole, requires
that the correct type of impression (posi�ve or
nega�ve) and orienta�on is used to make a comparison between
the unknown and the known mark.
Bitemark evidence is not as accepted for individualiza�on toda
y as
it was during Ted Bundy’s trial.
Associated Press
7.2 Collec�on and Preserva�on of Pa�ern Evidence

There are different ways of collec�ng pa�ern evidence, depend
ing on the markings or impressions le� behind. Two important t
erms to know are posi�ve and nega�ve impressions. A posi�ve
impression is
iden�cal to the object that made it, whereas a nega�ve impressi
on is its mirror image. The shoe prints le� in the mud are nega
�ve impressions; they are nega�ves of the shoes’ soles. In this
scenario, the
posi�ves would be the shoes’ soles. The same is true in the case
of a �re indenta�on. This mark would be collected by cas�ng.
The resul�ng cast is a posi�ve, like the �re that made the mar
k, so the cast can
be compared to the �re.
In general, imprint markings are collected by first photographin
g the mark with and without a scale present, and then either coll
ec�ng the whole object that has the mark, or if that is not possi
ble, by tape
li�ing. If the imprint markings are made up of dirt or grease or
other residues, they can be li�ed from a surface with s�cky tap
e (similar to Scotch® tape). The tape must be placed onto the su
rface with care, to
avoid crea�ng any bubbles. A rubber roller can help in this pro
cess. Then the tape is carefully li�ed, so as to avoid any damag
e to or distor�on of the mark, and placed onto a contras�ng bac
king surface. A
black mark, for example, would be placed onto a white backing
surface. This item is then labeled with the usual required inform
a�on and placed into a paper or plas�c container and sealed. Li
�ing tapes of
various sizes and appropriate backings are commercially availab
le.
Indenta�on markings must also be photographed. As men�oned
earlier, side ligh�ng helps give the impression be�er contrast.
A�er photography, the mark is cast. For

this purpose, dental stone is used. This is a special finely groun
d plaster used by den�sts to make molds for restora�ons. It is
mixed with water to make a pancake‐
ba�er consistency mixture, then poured into the indenta�on so
as not to disturb any of the detail present. Once it hardens, it ca
n be removed. It captures fine detail
quite well. In addi�on to labeling the packaging of a cast, the c
ollector can scratch a case number or item number into the top s
ide of the hardening dental stone.
There are special types of cas�ng materials for tool marks, for
marks in snow, and other specific types of marks. Tool marks ar
e discussed in a later chapter, but for
now, dental stone is not capable of capturing the very fine detail
in a tool mark (like a stria�on mark made by a screw driver on
a lock plate). There are silicone‐based
materials commercially available that are be�er suited for this t
ask. These silicone‐based materials can also be used for indenta
�on‐type fingerprints, such as a
fingerprint in wax. Indenta�on markings in snow pose a proble
m because dental stone gives off heat as it hardens, and the heat
can melt the snow and destroy the
impression detail. Products like Snow Print Wax can be sprayed
onto the mark to protect it from this effect. An indenta�on imp
ression is a nega�ve, and so the cast of
the impression is a posi�ve. Accordingly, the cast can be compa
red directly with the �re or footwear or other item that is thoug
ht to have made the indenta�on.
Both in collec�ng evidence and in thinking about how pa�ern c
omparisons are done, it is important to remember that compariso
ns must be made between like
impressions. Le� with le�, right with right, posi�ve with posi
�ve, and nega�ve with nega�ve. The detailed individual chara
cteris�cs that help in individualizing the mark
must be in the same orienta�on as the original object that made
the mark (or as its mirror image). Some�mes, this requires that

the lab create a known from the
suspected item in order to make the comparison. For example, a
li�ed footwear impression from a scene would be compared wit
h an inked impression of the
suspected footwear made in the laboratory.
Think About It
Imagine you are a pa�ern evidence examiner, and the police bri
ng you a tape‐li�ed impression of a �re they have go�en from
a flat concrete surface. They have a suspect car, but it is up to y
ou to figure
out how to compare the �res with the impressions. How would
you make the known specimens from the �res to use for compar
ison with the ques�oned impression?
7.3 Analysis of Pa�ern Evidence
In Chapter 1.4 (h�p://content.thuzelearning.com/books/AUCRJ
311.13.1/sec�ons/sec1.4#sec1.4) , class and individual characte
ris�cs were introduced. These concepts become very important
in physical pa�ern analysis.
Consider items like shoes or �res. There are hundreds, or mayb
e even thousands, of iden�cal shoes and �res in the world. The
y were manufactured under quality control standards to be as si
milar as possible.
So, if a brand new shoe or �re leaves an impression, what chara
cteris�cs make up that impression? Class characteris�cs. With
a new shoe, the sole pa�ern, manufacturer, size, type of shoe, e
tc., can be
determined. However, it is impossible to dis�nguish any individ
ual shoe in that class, because there are not yet any individual c
haracteris�cs. The same rule applies to �res. Individual charact
eris�cs come about
as a result of wear. Sole or �re pa�ern features wear down in n
on‐uniform ways, parts of the sole or �re can be cut or torn by
wear, foreign objects can make unusual marks in the sole or �re

material, and so
on.
The forensic examiner will make a comparison between a ques�
oned mark and a known object. If you recall, ques�oned objects
are found at the scene and have an unknown source. Known obj
ects have a
known source and can help to determine the source of a ques�o
ned object. Here, the ma�er of ques�oned and known specimen
s becomes a li�le more complicated with the inclusion of posi�
ve or nega�ve
impressions. A sneaker sole itself, for instance, cannot be comp
ared with the impression mark because posi�ves and nega�ves
cannot be compared directly. The features of interest would be
mirror‐imaged. Take
a good look at Figure 7.1.
Figure 7.1: Sneaker sole impressions
The figure shows a right sneaker, but it is a mirror image with r
espect to the inked impression on the brown paper. To make a c
omparison, the sneaker must be used to make a known nega�ve
impression. This
might be an inked impression on paper, or on transparent plas�
c. These are good surfaces for capturing the detail in the footwe
ar in approximately the same way as it was captured in the evid
ence mark. Note
that these inked impressions would be made by someone actuall
y wearing the sneaker and taking a step, so that there would be
weight on the shoe. The middle impression on transparent plas�
c in Figure 7.1
is turned to match the orienta�on of the sneaker in the picture,
but if it is turned over, it will match the orienta�on of the paper
print. As an inked sneaker impression, it is a nega�ve, and ther
efore could be
used as the known for an unknown imprint thought to have been

made by that sneaker. You can also see from Figure 7.1 how it
would be easy to confuse le� and right if you don’t keep track o
f what you are
doing when making these impressions on transparent surfaces.
Physical Matches
There are four criteria that must be met in order to state that evi
dence is individualized in a fracture match. The criteria include:
1. The objects must be broken or torn or cut.
2. They must be capable of being realigned.
3. There must be a jigsaw fit (or lock and key fit) surface to sur
face.
4. The match must be unique.
With indirect or secondary matches, such as torn fabrics, it is u
nlikely that individuality can be declared, even if the pieces app
ear to fit. It isn’t intui�ve that every fabric cut or tear will be c
ompletely random
and thus unique. This means that there is a possibility of a chan
ce duplicate. Two different cuts, or even tears, of a fabric could
be so similar as to be indis�nguishable in a comparison.
Physical matching is done by the eye, or with the aid of a magni
fier or stereo microscope. This is a microscope with two eyepiec
es (enabling stereo vision) that is essen�ally a magnifier. This t
ype of matching is
intui�ve and quite familiar to people. As a result, it is very con
vincing for a jury or judge, because they can look at it and see i
t for themselves.
Impressions
With the other impressions that have been discussed, such as th
ose from shoes or �res, the comparison is more subjec�ve and

will depend on the examiner’s training and experience. These co
mparisons are
also done by the eye or with the aid of simple magnifiers. The i
ndividual characteris�cs must be located and their posi�on wit
hin the overall pa�ern noted. With experience, examiners devel
op a sense of what
the different individual characteris�cs are in each impression. T
hey also learn to judge the quality of the impression and how m
any individual characteris�cs it possesses. As you can imagine,
not every
impression gives good detail. It might be light, or smudged, or d
istorted. Examiners use these factors to determine if known and
unknown markings match. There is no rule about how many mat
ching individual
characteris�cs must be present to declare that the known is the
source of the ques�oned. This determina�on is up to the exami
ner and is thus more subjec�ve. Unlike a physical match, these
comparisons are
not intui�ve or obvious, and the skill to do them comes only fro
m extensive training and experience.
As with the random fracturing of solid objects, individuality du
e to wear comes about because the accidentals, the individual ch
aracteris�cs acquired by the item, are expected to be random.
With a sneaker
sole, for example, this might be a cut or a par�cularly worn are
a. An examiner must use his or her training and judgment to ass
ess the quality of the impression, and the number and distribu�
on of individual
characteris�cs that were transferred to the mark from the object
. These factors help the examiner to decide what conclusion to d
raw from the comparison.
Other pa�erns can fall into this general category. Occasionally,
a lip print or ear print is examined. These imprints are unusual,
so there is not much examiner experience with or research on th

em. Thus, there is
not much of a basis for finding enough individual characteris�c
s to reach an unambiguous conclusion. Sock prints or glove prin
ts may be included here, as well as fabric impressions, such as
when a blood‐
soaked fabric is pressed against a nonabsorbent surface and leav
es an impression in blood. Some�mes, in a hit‐and‐run case, the
pa�ern of the fabric from the clothing of a vic�m can be impre
ssed into the
bumper of a vehicle.
Bitemarks can be included here, as well. Only forensic odontolo
gists deal with bitemark comparisons, but these marks can be co
nsidered members of the pa�erns for individualiza�on category
. Bitemarks are
complicated because different numbers of teeth might make the
m, they are frequently on curved surfaces that can change or shr
ink, and it is difficult to prepare truly proper knowns for compa
rison from a
suspect’s teeth. One can make models (casts) of someone’s teeth
, but it is not easy to reproduce the eviden�ary mark, because t
hey are usually on living skin and the surfaces are o�en curved.
Up un�l around
ten years ago, forensic den�sts some�mes declared that a bitem
ark could be individualized and could iden�fy a par�cular pers
on. There were a number of cases where bitemark evidence figu
red in a criminal
convic�on.
One famous example of these cases occurred in the Florida trial
of the serial murderer Ted Bundy. Ted Bundy was one of the mo
st prolific serial
murderers in U.S. history. He is known to have killed dozens of
women in Washington, Oregon, Idaho, Utah, Colorado, and Flor
ida, and inves�gators
familiar with him think there were many others. His en�re story

is long and complicated, but the bitemark evidence against him
came in the
murder of two Chi Omega sorority sisters, and the assault on tw
o others, in their sorority house at Florida State University in Ja
nuary, 1978. Two
forensic odontologists tes�fied that the bitemarks on the murde
red women were from Bundy. Bundy was executed on January 2
4, 1989. Leading up
to his execu�on, he talked to inves�gators from several of the
western states where he had lived; he confessed to a long list of
murders, some of
which the police hadn’t even known about. He was such a skille
d liar, however, that police could never be sure how many vic�
ms there really were.
More recently, however, there were a couple of cases in which t
here was saliva around the bitemark on the vic�m, and later DN
A typing showed
that the saliva did not match the person whom the forensic odon
tologist had posi�vely iden�fied. As a result, bitemarks are not
generally
a�ributed to a specific person any more. It is more likely that a
den�st will say that the person is excluded, or could not be excl
uded.
Think About It
Bitemarks are no longer considered to be a way to specifically i
den�fy someone, but they can be used to exclude or include a p
erson of interest. Do you think that if Ted Bundy were on trial t
oday, the
bitemarks would s�ll be a key piece of evidence against him? If
you were the odontologist tes�fying in the trial, how would yo
u explain the bitemarks to the court?
Individualiza�on

The term individualiza�on has been used frequently in this disc
ussion. The term means uniqueness—one of a kind—
the only one—
to the exclusion of all others. Recently, there has been discussio
n among
pa�ern analysts about whether uniqueness is a realis�c conclus
ion based on their knowledge of and experience with many of th
ese pa�erns. How is anyone sure there is no chance duplicate an
ywhere? There
has been a trend in the direc�on of changing the terminology to
describe persuasive matches as a single source (Polski et al., 20
11). If a phrase like a�ributable to a single source were to be us
ed and defined in
an understandable way that suggested a strong possibility of ind
ividuality or common origin, but permi�ed some uncertainty, it
could be a be�er reflec�on of the state of knowledge. Experime
nts on pa�ern
matching will con�nue, but in truth there is no way to compare
any given pa�ern with every possible source. Even if a single p
a�ern were studied, for example, a stria�on toolmark made by
a screwdriver on a
scratchable surface, it is nearly impossible to replicate. The ang
le, the pressure, the speed of movement—
these could all affect the appearance of the final mark. And that
is only in one surface! So, we have to
rely on the scien�fic concept of induc�on. If we have good inf
orma�on on basic principles about a representa�ve number of p
ossible situa�ons, we can, by induc�ve logic, extend them to c
over all the marks in
that category.
https://content.ashford.edu/books/AUCRJ311.13.1/sections/sec1
.4#sec1.4

Everyone is familiar with the no�on of using fingerprint eviden
ce to
�e a suspect to a crime. Do you think the idea of fingerprints is
ever misconstrued by jurors as part of the CSI Effect?
Jeff Schrier/The Saginaw News/Associated Press
Can you see the differences between the fingerprint pa�erns? W
hich pa�ern is on your fingers?
Now that you know the fingerprint pa�erns on your fingers, exa
mine them again. Can you find examples of the key
minu�a features?
The idea of the uniqueness of an
individual’s fingerprints goes way
back in history, as demonstrated by
Thomas Bewick’s use of his
thumbprint as his signature mark.
Michael Nicholson/Historical/Corbis
7.4 Fingerprints
Among the oldest and best‐established individualizing markings
, fingerprints remain one of the most important types of physica
l evidence in the repertoire. A fingerprint impression from a sce
ne matched to the
known fingerprint of a suspect essen�ally proves that the perso
n was there at some point. Almost everyone believes that finger
prints are highly individual. It has become part of our unspoken
culture. People
talk about "DNA fingerprin�ng" and use the term "unique" to d
escribe a fingerprint.
Fingerprints are a form of biometric iden�fier, a biological mea
surement or feature of a person that has the poten�al of being u

sed as the basis for individualiza�on. Other types of biometric i
den�fiers include
DNA; facial features; parts of the eye, such as re�nas and irises
; and even handwri�ng.
There is interest in biometrics as individuality markers because
they are difficult to reproduce or forge. All documentary iden�f
ica�on systems have
been subject to forgery, including driver’s licenses, passports, c
redit and debit cards, and employee iden�fying cards or badges,
making it possible
for a criminal to change his or her iden�ty. This is more difficu
lt and less common with biometric markers.
Fingerprints are an a�rac�ve biometric because they are forme
d during a person’s development in the womb, are permanent an
d unchanging
throughout life, easy to record and scan unobtrusively, and invo
lve a bare minimum of privacy invasion to record. Something to
remember about
the use of fingerprints as biometric iden�fica�on vehicles is th
at the goal is not to individualize the person among everyone in
the world. That is
not necessary. A system might be put in place to dis�nguish em
ployees who work in a large, secure defense plant, or every airli
ne passenger who is
a frequent flyer with United Airlines. It is possible to determine
how many features an automated scanning system has to dis�n
guish on how many
different fingers to tell apart some specific number of people. T
he theory behind this technology is, of course, the basis for auto
mated fingerprint
iden�fica�on systems. And, it is important in ge�ng at the que
s�on of fingerprint individuality, because it represents an auto
mated method for
comparing large numbers of prints for individual characteris�cs

.
Nature of Fingerprints
The beginning of the recogni�on of fingerprints as a unique per
sonal iden�fier is shrouded in the mists of history. Fingerprints
are the result of a
type of skin, fric�on ridge skin, which is found on the ends of t
he fingers, in the palms, and on the soles of the feet of primates,
including humans.
Though palm prints and footprints can be compared and analyze
d, the most work has been done on fingerprints.
As shown in Figure 7.2, there are three basic fingerprint pa�ern
s: arches, loops, and whorls.
Figure 7.2: Three basic fingerprint pa�erns
An important development in the history of fingerprints was cla
ssifica�on systems. Classifica�on schemes are based on all ten
prints from an individual. The basic pa�ern is determined from
each print and
within the basic pa�erns, fingerprints have certain ridge feature
s that they all share. Fingerprint examiners call these features m
inu�ae (singular: minu�a) and three of them are important to fi
ngerprint
examiners when they compare prints. These are the dot, the bifu
rca�on, and the ridge ending (see Figure 7.3). Note that these m
inu�ae can be present in more than one place in the print pa�er
n, and that the
loca�on varies from print to print. The type, number, and loca�
on of minu�ae within a print form the basis of its individuality.
Figure 7.3: Key minu�a features
Think About It

Compare the pa�erns and minu�ae of your fingerprints with fri
ends or family members. Do you see the differences? Do you thi
nk fingerprints are an accurate and reliable way to iden�fy peo
ple?
Can Fingerprints be Altered?
History of Fingerprints for Iden�fica�on
There are indica�ons from archaeological excava�ons that the
use of fingerprint and handprint pa�erns as methods of personal
iden�fica�on dates back thousands of years (Berry & Stoney,
2001). They are
thought to have been used as signatures and marks of authen�ci
ty.
The study and use of fingerprints as unique iden�fiers can be tr
aced to the 17th and 18th centuries in Europe. The English plant
morphologist Nehemiah Grew (1641–
1712) published very accurate drawings and
descrip�ons of ridge pa�erns in a paper called "The Descrip�o
n and Use of the Pores in the Skin of the Hands and Feet," in th
e Philosophical Transac�ons of the Royal Society of London (1
684). Then Johannes
Evangelista Purkinje (1787–
1869), a Czech physiologist, wrote about fric�on ridge pa�erns
and described a number of fingerprint pa�erns in his thesis in
1823. Thomas Bewick (1753–1828) was primarily known
as a wood engraver whose engravings appeared in books. He ap
pears to have "signed" his work with his own thumbprint, believ
ing it to be as unique as his signature.
Bri�sh civil servants in India, beginning around 1850, were imp
ortant contributors to the development of fingerprints as a mean
s of personal iden�fica�on. Sir William Herschel,

one such person, is o�en credited with being the first European
to recognize the value of fingerprints as a means of iden�fying
individuals. Dr. Henry Faulds, a Sco�sh physician,
is known to have been involved in the study of fingerprints at le
ast by 1879. Faulds noted that fingerprints could be classified a
nd that ridge detail appeared to be unique, and
he men�oned the idea of apprehending criminals by loca�ng fi
ngerprints at scenes. He wrote to Charles Darwin (the scien�st r
esponsible for proposing the theory of evolu�on)
about fingerprints, who then forwarded the le�er on to Francis
Galton. Galton was a well‐known scien�st and early gene�cs re
searcher, who has been said to have put the study
of fingerprints on scien�fic foo�ng. Galton became interested i
n the subject of fingerprints and put much thought into figuring
out how to show that fingerprints were individual.
Fingerprint minu�ae are some�mes called Galton features in re
cogni�on of his contribu�ons. Thomas Taylor, a U.S. Departme
nt of Agriculture microscopist, noted in a scien�fic
journal ar�cle in 1877 that fingerprints and palm prints might b
e used as iden�fica�on features, especially in criminal ma�ers.
To understand and appreciate how fingerprints came into widesp
read use, some background on a technique called anthropometry
is necessary. Anthropometry involves the
measurement of the human body and its parts, and can be regard
ed as the first recognized biometric iden�fica�on method. This
method was created by Alphonse Ber�llon
(1853–
1914) and laid the founda�on for the eventual acceptance of a b
iometric parameter as an objec�ve basis for personal iden�fica
�on in a law enforcement context. Ber�llon
came up with this concept while working with the Paris Police P
refecture, where his du�es included filling out and filing crimin
al informa�on cards. The criminals were skilled at
avoiding iden�fica�on by using disguises and aliases. It occurr
ed to Ber�llon that individual physical features could be used t

o uniquely iden�fy people on criminal records, and
he developed a system of measurements that included head size,
finger length, and so forth, ul�mately choosing 11 different me
asurements. The informa�on was recorded on
file cards and a system was devised for organizing the files. His
superiors doubted the system, but it soon proved its value by en
abling the police to iden�fy repeat arrestees even
if they provided alias names. Ber�llon eventually became direct
or of the iden�fica�on bureau of the Paris Police. Police agenci
es in many other places began to use his system—
o�en called Ber�llonage. Its ul�mate undoing was the unequiv
ocal proof that different individuals could have the same anthro
pometric measurements.
A well‐known example of this chance duplica�on came at the L
eavenworth Prison in the U.S. A new prisoner named Will West
was having his measurements taken when a staff
member began to suspect that he had encountered this profile be
fore. Upon inves�ga�on, he found that the same measurements
fit a man named William West who was
already incarcerated at the prison (and unrelated to Will West, a
lthough they looked a lot alike). However, the two did have diff
erent fingerprints. This incident, and others like it,
eventually convinced police iden�fica�on specialists that finge
rprints represented the basis for a superior method of personal i
den�fica�on.
Around 1893, the Bri�sh Home Office, parent agency of the Lo
ndon Metropolitan Police (Scotland Yard), decided to add finger
prints to the Ber�llon cards for criminals in their iden�fica�on
system. Before long,
the success of fingerprints overshadowed that of Ber�llonage in
criminal iden�fica�on, and anthropometry was abandoned in 1
901.
Sir Edward Henry (1850–

1931) was a member of the Bri�sh Indian Civil Service, beginni
ng in about 1873. In 1891, he became inspector general of polic
e for Bengal province, where anthropometry was in use for
criminal iden�fica�on. He became interested in fingerprints, re
ad Galton’s book, and corresponded with and later visited him.
Galton shared all the informa�on he had about fingerprints with
Henry, including
materials he had obtained from Herschel and Faulds. Henry is w
idely known for working out a fingerprint classifica�on system
that was adopted in Bri�sh India, and presented to people in the
U.K. in 1899. He
wrote a classic book en�tled Classifica�on and Uses of Fingerp
rints.
Juan Vuce�ch (1858–
1925) was the western hemisphere’s fingerprint pioneer. An em
ployee of the police department in La Plata, Argen�na, he beca
me convinced of the value of fingerprints as a means of
criminal iden�fica�on and wrote a book on the subject in 1894.
By 1896, the Argen�ne police had abandoned Ber�llonage in f
avor of fingerprints in criminal records. The first recorded case
in which fingerprints
were used to solve a crime took place in Argen�na in 1892. A
woman named Francisca Rojas alleged that her two children wer
e murdered by a man named Velasquez. Inves�gators examined
her home and
found a bloody thumb print on the bedroom door. Vuce�ch com
pared the fingerprints of Rojas and Velasquez to the bloody fing
erprint, and found it belonged to Rojas, linking her to the murde
r of her children.
Vuce�ch devised a classifica�on system for fingerprints that w
as used in Argen�na and throughout South America.
In North America, fingerprints were in use by the New York Cit
y civil service (to prevent impersona�ons during examina�ons)
by 1903, and fingerprints were introduced about the same �me

in the New York
State prison system and at the Leavenworth Peniten�ary. A num
ber of police departments began using fingerprints as iden�fiers
in criminal records as well. The 1904 St. Louis World’s Fair pr
ovided the venue for
a chance mee�ng between Inspector Edward Foster of the Royal
Canadian Mounted Police and Detec�ve John Ferrier of Scotla
nd Yard. As a result of what he learned in St. Louis, Foster con
vinced his superiors
in the R.C.M.P. of the u�lity of fingerprints. In 1910, a man cal
led Thomas Jennings was arrested in Chicago and brought to tri
al for murder. The primary evidence against him was fingerprint
s. The state wanted
to ensure that the fingerprint iden�fica�on evidence would sur
vive the an�cipated appeal to the Illinois Supreme Court, and th
ey called Edward Foster as an expert witness. The defendant wa
s convicted, the
evidence did survive, and the Jennings case is considered a land
mark fingerprint case in criminal jurisprudence.
Fingerprint Iden�fica�on Organiza�ons
Now that fingerprints have become a major biometric indicator
and play an important role in criminal inves�ga�ons, there are
a couple of important organiza�ons that fingerprint examiners
may choose to
become a part of. The Interna�onal Associa�on for Iden�fica�
on (IAI) is the primary professional organiza�on for fingerprint
examiners. It has extensive cer�fica�on programs and its laten
t print cer�fica�on is
difficult to obtain. Many physical pa�ern comparison specialist
s also belong to the IAI.
Another important group is the Scien�fic Working Group on Fri
c�on Ridge Analysis, Study and Technology (SWGFAST). This
commi�ee is a consensus standard se�ng body for all comparis

ons involving fric�on
ridge skin (fingerprints, footprints, palm prints, etc.). It has alre
ady adopted a number of consensus standards, including standar
ds for assigning single source a�ribu�on.
Fingerprint Classifica�on and File Storage
When all fingerprint records consisted of inked impressions on
a ten‐print card, a classifica�on system was very important. Ho
w else could the cards be filed so that they were easily found? C
lassifica�on was
based on a ten‐print card, not on a single print. You needed all t
en prints from a person to classify the prints.
In most criminal cases where fingerprints are recovered, there is
only one—or some�mes only a par�al—
impression of one finger. In such a case, how would you locate i
t in your card file? Simply put, you
couldn’t, which was the problem. Some�mes, there might be on
e or more suspects, and their fingerprints could be pulled for co
mparison. But if there weren’t any suspects, there was no realis
�c way to search
drawers that were full of files to look for one fingerprint. That i
s why the advent of automated fingerprint iden�fica�on system
s (AFIS) revolu�onized the use of fingerprints.
The system consists of a scanner that records images of all ten p
rints and stores them on a server. It includes many worksta�ons
from which operators can enter new fingerprints, and search the
system for
exis�ng ones. The way in which the system works is rela�vely
simple. The examiner begins by scanning a fingerprint and com
puterized algorithms mark the minu�ae to search for. The comp
uter then calculates a
score based upon the degree of match. Most of the �me, the mat
ching print will appear in the first few entries, if it is in the syst

em. The examiner must pull up the likely matches and compare t
hem with the
fingerprint in ques�on. The computer is not used for the purpos
es of matching prints for court purposes. That is something only
an examiner can do. AFIS is used to provide possible matches,
helping narrow
down the list of individuals the fingerprint could belong to. An
examiner will then need to compare the fingerprint and the poss
ible matches provided to make the final decision on the iden�fi
ca�on of the
fingerprint.
Think About It
Do you think that ten‐print cards and/or AFIS systems are a goo
d way to organize and store fingerprint data? What other ways c
an you think of that could improve the filing system?
Fingerprint collec�on done the old‐fashioned way consisted of
inking each individual finger and organizing the impressions on
to a
single card. How has modern technology improved this process?
iStockphoto/Thinkstock
If fingerprints are to be found at the scene of a crime, they are
most likely to be latent ones found a�er an inves�gator has dus
ted
for fingerprints.
Joe Johnston/The Tribune (of San Luis Obispo)/Associated Pres
s
Don Ryan/Associated Press

7.5 Collec�on and Preserva�on of Fingerprints
There are two topics that must be considered in terms of collec
�ng and preserving fingerprints for a case. The first is collec�n
g or taking
fingerprints from known individuals. The second is collec�ng fi
ngerprints from crime scenes and objects.
Collec�on and Preserva�on of Knowns
At one �me, fingerprints were taken from known individuals by
inking the fingers and impressing them onto fingerprint cards. I
n addi�on to
including a labeled box for each finger, there was space on the b
o�om of the card to reprint the thumbs, and to impress the four
fingers of each
hand. These impressions served as back‐ups if the main boxed i
mpressions were not of high enough quality for a comparison. F
ingerprints from
these ten‐print cards can be scanned into AFIS systems to build
the single print databases.
Today, most fingerprints are collected by Live Scan technology.
The person places each finger (and thumb) onto a small scannin
g plate. Some�mes,
there is an on‐screen guide to help the person adjust the posi�o
n and pressure of each finger. The device then scans the prints d
irectly into an
AFIS. These devices can be seen at ports of entry into the Unite
d States, such as in interna�onal airports.
Fingerprints are also preserved electronically. The largest datab
ase of fingerprints is contained in the FBI’s integrated AFIS (IA
FIS) system. The system
contains over 70 million print files from criminal histories, and
about 35 million other files. People who are arrested are fingerp

rinted. But many
other people may be fingerprinted as well, like those who have f
irearms permits or security clearances or have undergone backgr
ound checks for a
variety of reasons.
Collec�on, Preserva�on, and Processing of Eviden�ary Prints
Collec�ng fingerprints from scenes is similar to collec�ng evid
ence from a scene, but it is more complicated than collec�ng kn
own prints. Some�mes, prints at scenes are visible, but o�en th
ey are not. The ones
which are not require some sort of development or processing to
render them visible. The first decision an inves�gator must ma
ke is whether to use development (visualiza�on) techniques for
prints at the
scene, or bring the object bearing the print back to the lab. The
larger and more unmovable the object or surface, the more likel
y an inves�gator would employ development techniques in the f
ield. A�er
loca�ng and/or developing the print or prints, the crime scene p
rocessor must either collect the whole object the print resides o
n, or collect the fingerprint alone. Photography and sketches are
used to
document the loca�on of the fingerprint, or the object containin
g it, at the scene. The print or developed print must also be phot
ographed. It is best if the photo can be 1:1 (life size image). Th
at way there is
no compression of the details. If a print has required developme
nt, it may be possible to tape li� the print, depending on the typ
e of development. All the usual rules about chain of custody per
tain here. The
item bearing the print or the tape li� must be carefully package
d, labeled, and sealed. Items have to be packaged so as to provi
de maximum protec�on of an undeveloped print impression. No
thing should

touch or rub the impression during storage or transport. Some ty
pe of wood or plas�c trough would have to be used to protect th
e ridge impressions from the package during transport. Develop
ed latents must
also be protected. Tape li�s are placed onto backings, and are t
hus protected.
There are three kinds of fingerprint impressions encountered: vi
sible, plas�c, and latent.
Visible Fingerprints
Visible prints are also some�mes called patent. Visible prints a
re made in dirt, ink, blood, or some other medium that is visible
to the eye. These would be photographed and, if possible, the o
bject on which
they are deposited would be collected.
Plas�c Fingerprints
Plas�c prints are three‐dimensional and are made in so� receivi
ng materials like silly pu�y or tar. These are indenta�on prints.
They are first photographed. Then, the object bearing the print
is collected, if
possible. If not, this type of fingerprint impression can be cast i
n the same manner as footwear indenta�ons, only the cas�ng m
aterials are silicone‐based and capable of capturing fine detail
much be�er than
any type of plaster.
Think About It
What do the techniques and procedures for eviden�ary fingerpri
nt collec�on and preserva�on have in common with the collec
�on and preserva�on techniques for other pa�ern evidence? W
hat are the

differences?
Latent Fingerprints
Latent fingerprints cannot be clearly seen or visualized without
some development or processing. There are three basic methods
of processing or
developing latent fingerprints: physical, chemical, and instrume
ntal. The most common and familiar physical method is powder
dus�ng. Here, a
fingerprint powder (usually black) is applied with a fine brush t
o the latent print residue. The powder par�cles adhere to the fa
�y components in
the residue and make the ridges visible. Another technique used
is called magna‐brush. Here a small magnet is used to apply ma
gne�c par�cles to
the print residue. These par�cles adhere to the latent residue th
e same way as the powder par�cles. Powder‐dusted (including
magna‐powder
dusted) prints can generally be li�ed using transparent tape. Th
e tape must be placed carefully onto the dusted print to avoid an
y air bubbles. This
can be done with a rubber roller. The tape is li�ed all in one slo
w mo�on, and the transparent tape li� is then placed onto a con
tras�ng
background, such as a white surface. Another more complex tec
hnique uses molybdenum disulfide par�cles in a solu�on. This
is known as "small
par�cle reagent" and works on surfaces that are wet. Li�ing of
a small par�cle reagent developed print can be accomplished wi
thout le�ng the
surface dry if the tape is carefully applied to the center and pres
sure applied in all direc�ons outward, pushing away the liquid
droplets in the
process. Latents on wet surfaces aren’t common, but the situa�
on does arise. Think of a can of beer with a latent on it, taken fr

om the refrigerator
and allowed to sit out in a humid environment for a while where
water can condense onto it.
The classical chemical techniques for print development were si
lver nitrate, iodine fuming, ninhydrin, and super glue. Silver nit
rate development
works on the same principle as the development of photographic
film, where silver chloride is chemically reduced to metallic sil
ver. Iodine fuming is
based on iodine molecules going from solid to vapor without be
coming liquid (a process called sublima�on). The iodine vapor
can interact with
fingerprint residue and give it a temporary color. The color can
be made permanent with other chemicals. Neither silver nitrate
nor iodine are used
for latent prints anymore because the other techniques are be�e
r or equivalent. Silver has go�en expensive, and it creates a dis
posal problem a�er
use. Other techniques are be�er than iodine because they have t
he poten�al for greater sensi�vity.
Today, ninhydrin or super glue treatment is followed by an addi
�onal treatment with other chemicals to make the visualiza�on
more sensi�ve—
that is, lesser amounts of residue can be detected. Ninhydrin is
a
chemical that reacts with the amino acids in fingerprint residue.
Amino acids are the building blocks of proteins. Super glue can
be fumed onto fingerprint residue where it reacts to form a semi
solid, whi�sh
deposit on the ridge pa�erns. Super glue will vaporize by itself,
and the process can be accelerated with heat. The vapors, or fu
mes, interact with the fingerprint residue. The super glued finge
rprint is fairly
permanent, but can be powder dusted, and the dusted print li�ed

. This is done in the same way as li�ing dusted fingerprints as d
escribed earlier. Super glued prints can also be further treated w
ith other
chemicals by dipping or spraying to make the visualiza�on mor
e sensi�ve. Ninhydrin is the method of choice for absorbent sur
faces like paper or sheet rock. Super glue will work on prac�cal
ly any surface.
The most common instrumental technique is called laser illumin
a�on. With this process, fingerprints are commonly developed
with super glue, on which a chemical called laser dye is applied.
When a laser is
shined on a fingerprint processed in this way, a very small amou
nt of residue can be visualized, and then photographed. Some�
mes, laser illumina�on is used directly on fingerprint residues,
but this technique
is used less frequently. Laser procedures are usually performed
in the lab. Portable lasers do exist, but these techniques are very
cumbersome in the field. Laser‐illuminated prints would typical
ly be
photographed for comparison. The laser dye procedure is indicat
ed if the ridge pa�erns are not clear enough for a comparison fo
llowing super glue alone.
Fingerprints in blood can be a special case. Some�mes, they are
plainly visible (in these cases these would be considered visibl
e prints), but at other �mes they may require special enhanceme
nt techniques. The
enhancement procedures make use of chemicals that produce col
or in the presence of blood. They also contain a s�cky substanc
e to make them adhere to the residue and a rapidly evapora�ng
solvent so that
bloody prints on a ver�cal surface don’t run when the chemical
is sprayed. These enhancement techniques have the poten�al of
interfering with DNA profiling of the blood as the chemicals in
the enhancement

mixture can adversely affect DNA. It is important for inves�gat
ors to consider the value of DNA profiling and fingerprint iden
�fica�on to the case in these situa�ons. A small specimen of b
lood could be
collected, for example, without disturbing the ridge pa�erns a fi
ngerprint examiner would need.
Think About It
If you had to choose a single method for processing latent prints
in the laboratory, which one would you choose, and why?
7.6 Analysis of Fingerprints
For forensic and legal purposes, fingerprint analysis or compari
sons are the heart of the ma�er. The comparison of a ques�one
d print with a known, and the ability to form an unequivocal con
clusion, make
fingerprints valuable as evidence.
Trained examiners complete the comparisons. The training is le
ngthy. It can take up to two years before a new examiner is allo
wed to operate without supervision. There is a specific protocol
to be completed
for each comparison. The first thing to be decided is whether th
e print is suitable for comparison. This decision is based on the
clarity of the ridges and the examiner’s judgment that a proper c
omparison can
be completed. For example, the examiner must determine if ther
e is enough of the print present in the impression and if there ar
e enough visible details (minu�ae). The examiner must also det
ermine if the
print is easily viewed, is not smudged, and does not have too ma
ny impressions overlaid on one another. If the print is judged to
be unsuitable for comparison, the examina�on ends. If the prin
t is judged to be
suitable, the ques�oned print must be properly oriented for com

parison with a known (a whole fingerprint). To perform an accu
rate examina�on, the print cannot be upside down or rotated 90
degrees. Next, it
goes through analysis, comparison, evalua�on, and verifica�on
(ACE‐V). Analysis consists of judging suitability, arranging co
rrect orienta�on, and judging the minu�ae content of the print.
The comparison part
is carefully figuring out if every minu�a feature in the ques�on
ed impression is also in the known, and in the same loca�on. Th
e evalua�on step is based on the examiner’s knowledge of and e
xperience with
print comparisons. How common or rare is this pa�ern? If the e
xaminer is sa�sfied that there is enough detail, and there are no
unexplained differences between the ques�oned and known, an
iden�fica�on
can be made. In the verifica�on step, another examiner is asked
to look at the prints and verify the first examiner’s conclusion.
As shown in Table 7.1, the main category to which the fingerpri
nt belongs (arch, loop, whorl, etc.), is some�mes called First Le
vel, or Level 1. The minu�ae present and their loca�on is some
�mes called Second
Level, or Level 2. There is a Level 3 as well, consis�ng of pore
s and ridge features. Level 3 is not always used because the first
two levels are nearly always sufficient for making an iden�fica
�on or determining
an exclusion.
Table 7.1: Fingerprint pa�ern levels
Level Pa�ern category
1 Arch, loop, or whorl
2 Minu�ae (such as dot, bifurca�on, and ridge ending)

3 Pore and ridge features
An examiner may reach three possible conclusions following a c
omparison: exclusion, inconclusive, or iden�fica�on. Exclusio
n means that the ques�oned print does not match the known pri
nt and therefore the
person to which the known print belongs is excluded. Inconclusi
ve means the examiner can neither make the iden�fica�on nor
exclude the person. There isn’t enough informa�on in the ques
�oned print.
Iden�fica�on means that this ques�oned print is a�ributable t
o the person who furnished the known.
Du�es of a Latent Print Examiner
In recent years, there have been ques�ons as to whether there is
a sufficient scien�fic underpinning to fingerprint comparisons
to warrant the iden�fica�on conclusion (Na�onal Research Co
uncil, 2009; Koehler
& Saks, 2010). How do we know fingerprints are individual? Th
e standard answer is that hundreds of thousands of prints have b
een compared, and no two have been found that are alike. This s
tandard answer
is correct, but one person did not analyze all of these pairwise c
omparisons. That is, the sum total of all the pairwise compariso
ns was done by many different people at different �mes. Furthe
rmore, an
examiner doesn’t compare a ques�oned print with millions of k
nowns; the ques�oned print is compared with only a few. With
AFIS systems, the mul�ple pairwise comparison argument is m
uch more
supportable. If a ques�oned print is searched within IAFIS and
found, that ques�oned print was compared with all the prints in
the database. To date, no one has found two or three matches—
only one (or
none, if the print isn’t in IAFIS). The fact that so many searches

have been completed lends considerable support to the individu
ality idea.
Think About It
From everything you have learned so far, do you think there are
two people who have exactly the same ten fingerprints? What ab
out two people who have one fingerprint iden�cal to one of the
other
person’s? What about two people who have a par�al of one fing
erprint iden�cal to the par�al fingerprint of the other person?
Nevertheless, a high profile case from 2004 has caused the think
ing to be reconsidered. The real ques�on is not so much whethe
r complete fingerprints are duplicated to the extent that a traine
d examiner can’t
tell them apart, but whether there is a chance to get a par�al du
plicate. That is, presented with an incomplete ques�oned impre
ssion, could there be two prints out in the world that could be in
terpreted to
"match"? See what you think a�er reading the case of United St
ates v. Brandon Mayfield.
Case Illustra�on: United States v. Brandon Mayfield
Brandon Mayfield was a Muslim a�orney prac�cing in Oregon.
He was a U.S. ci�zen and Army veteran. He converted to Islam
a�er mee�ng and marrying his Egyp�an‐born wife. On March
11, 2004, a series
of coordinated bombings did extensive damage to Spain’s comm
uter train system in Madrid, killing 191 people and wounding ar
ound 1,800 others. The a�ack was perpetrated by a local terrori
st cell, inspired
by but not directly connected to Al Qaida. In the subsequent inv
es�ga�on, a bag containing detona�ng devices was recovered
by the Spanish police and latent fingerprints were found. These

were shared
with other countries’ law enforcement agencies to help with the
case.
The FBI fingerprint unit ran an AFIS search and generated a nu
mber of poten�al matches. Mayfield’s prints were among them.
Possibly because he was Muslim and
had provided legal assistance to some Muslim clients, he becam
e a principal suspect. FBI fingerprint experts working on the cas
e came to the conclusion that the
eviden�ary latents matched Mayfield, and several of them—
all highly experienced and seasoned examiners—
agreed on this conclusion. The FBI conducted a detailed
inves�ga�on of Mayfield, and eventually arrested him. There w
ere discussions and at least one mee�ng between FBI examiners
and Spanish fingerprint examiners, in
which the la�er told the FBI that the prints did not match Mayfi
eld. However, the FBI con�nued the inves�ga�on un�l it beca
me clear that the FBI was incorrect on
this iden�fica�on. It was found that the prints belonged to an
Algerian na�onal named Ouhnane Daoud.
The FBI released and apologized to Mr. Mayfield and the gover
nment se�led a suit he filed against it for $2 million. There was
a public discussion involving federal
overreach in the inves�ga�on, aside from the fingerprint issue.
Mr. Mayfield sued the government seeking to overturn parts of t
he PATRIOT Act (New York Times,
2006).
Reflect On It
Analyzing palm prints is not as common

as fingerprints, as fingerprints are more
prevalent. Do you think fingerprints show
more differences between individuals than
palm prints do?
Orlin Wagner/Associated Press
Reflect On It
What do you think about the misiden�fica�on of this case? Wa
s it bias, incorrect examina�on of the fingerprints, or a combina
�on of both that led to the wrong arrest? What do you think cou
ld have
prevented this?
It has been suggested by fingerprint cri�cs that misiden�fica�
on occurred in this case because of examiner bias. They state th
at FBI experts knew all about the case, and thought it should be
a match, and that
knowledge ended up deeply prejudicing them. In any event, it d
oes show that iden�fica�on errors can happen.
You may be thinking as you read this sec�on and this case exa
mple, why isn’t there a minimum number of points to define a m
atch? It sounds easy, but it isn’t. There was such a criterion in t
he United Kingdom
for quite some �me. But, it turned out that non‐matching finger
prints could have the minimum required number of points. It is
also the case that an examiner may not always have the minimu
m number, but is
convinced the prints match. For these reasons, the IAI, the profe
ssional organiza�on that makes interna�onal consensus stateme
nts about these ma�ers, has long taken the posi�on that there s
hould not be a
specified number of matching minu�ae or points to declare a m
atch. As noted, the IAI is con�nuing to examine its principles r

egarding fingerprint iden�fica�on (Polski et al., 2011).
Another way of looking at examiner accuracy is through profici
ency tests. Examiners are subjected to these proficiency tests fo
r cer�fica�on and recer�fica�on. Some agencies and accredite
d forensic labs also
par�cipate in proficiency tes�ng for their examiners. At �mes,
the tests can be done for research purposes as well. In proficien
cy tests, examiners are given sets of ques�oned prints or par�al
s along with known
prints, and told to complete pairwise comparisons and form con
clusions. The vast majority of tests and studies of this type sho
w that the examiners get the right answers. One study involving
the fingerprints of
iden�cal twins resulted in a few misiden�fica�ons (Grieve, 19
96). Iden�cal twin fingerprints are dis�nguishable, but they ca
n be very similar.
Analysis of Other Fric�on Ridge Impressions
Fric�on ridge skin impressions, such as palm prints and footpri
nts, are compared in the same way as fingerprints are compared.
To clarify, o�en�mes people refer to "footwear impressions" a
s footprints, but
this is incorrect. Footprints are made by bare feet. The main diff
erence between these types of fric�on ridge skin impressions an
d fingerprints is that files of palm or footprints are not maintain
ed because these
impressions are less frequently encountered than fingerprints. G
enerally, inves�gators must develop one or more suspects, then
arrange to collect inked palm or foot
impressions as knowns for comparison. The methods used for co
mparison and the criteria for conclusions are the same as for fin
gerprints.

Ch. 7 Conclusion
Pa�erns are an important class of evidence. Iden�fica�on pa�
erns refer to the mental images used to classify objects in the en
vironment. Individualiza�on pa�erns can be physical pa�erns
or impressions. The
most commonly seen impressions are footwear and �re tracks.
Reconstruc�on pa�erns help inves�gators form theories about
events that took place in the past, based on the physical evidenc
e record.
Pa�ern evidence is collected by photography, li�ing, and cas�
ng, as appropriate. It is analyzed by comparing a ques�oned im
pression with a known impression or object. A proper compariso
n requires that only
like impressions be compared (posi�ves, nega�ves, le�, right,
etc.). Some pa�ern evidence can some�mes be individualized.
Fingerprints are an important category of evidence, and have a l
engthy history of use as a means of personal iden�fica�on. Aut
omated fingerprint iden�fica�on systems have enabled the stor
age and search of
single fingerprints, and rendered ten‐print cards and classifica�
on systems obsolete. At scenes, visible, plas�c, and latent print
s can be found. Latent prints require some visualiza�on techniq
ues to make the
ridge detail suitable for comparison. There are physical, chemic
al, and instrumental methods for developing latent prints. Ques
�oned fingerprints are compared with known prints, and examin
ers can o�en
individualize the print to a person, or exclude a person as the so
urce. Some�mes, prints are not suitable for comparison, or ther
e is insufficient detail to reach a conclusion. There has been dis
cussion about the
scien�fic basis for fingerprint individuality, and whether indivi
dualiza�on is jus�fied in fingerprint comparison, par�cularly
with ques�oned par�al prints. Palm prints and footprints are so

me�mes encountered at
scenes, and they may be compared to knowns in the same way a
s fingerprints.
Ch. 7 Learning Resources
Key Ideas
There are pa�erns for iden�fica�on, for individualiza�on, and
for reconstruc�on.
Important pa�erns for individualiza�on include physical match
es, as well as imprint and indenta�on markings, of which footw
ear and �re impressions may be the most common.
Fingerprints are an important class of physical evidence and an
example of a biometric iden�fier.
AFIS systems enable rapid search and retrieval of single fingerp
rints.
Latent fingerprints require visualiza�on or processing steps in
order to be suitable for comparison.
There is a method for fingerprint (and other fric�on ridge print)
comparisons called ACE‐V, which describes the steps an exami
ner follows to compare ques�oned and known prints.
Fingerprints are individual. With very rare excep�ons, iden�fic
a�ons or exclusions can be made following a comparison by a q
ualified examiner.
Foot and palm prints are compared in the same manner as finger
prints.
Cri�cal Thinking Ques�ons
1. In a criminal aggravated assault case, the accused ripped off t
he vic�m’s dress, and in the process, a piece became completel
y separated and got stuck on the back of the perpetrator’s shirt.
The police later
recovered the shirt, which s�ll had the fragment of dress on it. I
magine that you are the lab examiner, comparing the fragment t

o the dress. This is a summer‐weight, light material with a dis�
nc�ve, decora�ve
pa�ern on it. The fragment lines up almost perfectly with a mis
sing area on the vic�m’s dress. Color and pa�ern are the same.
Thread count is the same. It definitely could be the missing piec
e. How would you
tes�fy to this finding?
2. In a criminal case, a suspect is thought to have kicked in a m
etal door while wearing a sneaker. The police successfully use a
n electrosta�c dust li�er to li� a good dust print of the sneaker
from the door. They
also have a suspect, and the sneaker they think probably made t
he mark. How would you, as the examiner, make the "known" sn
eaker impression to compare with the dust print?
3. A government agency is willing to fund a study to establish t
hat fingerprints are really individual. How would you design thi
s study? Describe the study design, the results that might be exp
ected, and the
conclusions that could be drawn from them.
4. In a homicide case, the police find a good bloody footprint on
a bathroom floor �le. They think the footprint belongs to the p
erpetrator. They have a suspect in custody, but they cannot prov
e he was at the
scene at the �me of the crime. You are the examiner and are giv
en the �le with the ques�oned footprint on it. How would you t
ell the police to collect the known footprints from the decedent
and from the
suspect? Do you think the police need a search warrant to collec
t the known footprint from the suspect?
5. You are the fingerprint expert witness in a criminal trial. An
object from the crime scene had a good latent print on it, and yo
u were able to match the latent to the known print from one of t

he defendant’s
fingers. You have tes�fied that the latent fingerprint came from
the defendant. The defense lawyer now says to you the followin
g: "The police had a ten‐print card on file containing the defend
ant’s fingerprints.
At the �me the police arrested the defendant, they had very li�l
e evidence that he was actually at the scene, but they were convi
nced he was their guy. Suppose they took some li�ing tape and
carefully li�ed
off one of the prints from the ten‐print card, then used that tape
to place the ‘latent print’ on the object from the scene that was
submi�ed to you for examina�on. Do you concede that this sce
nario is
possible? If so, would you agree that the latent match to the def
endant does not then prove that he was actually at the scene?"
Key Terms
Click on each key term to see the defini�on.
accidental
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ns/front_ma�er/books/AUCRJ311.13.1/sec�ons/front_ma�er/b
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r/books/AUCRJ311.13.1/sec�ons/front_ma�er/books/AUCRJ31
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ont_ma�er/books/AUCRJ311.13.1/sec�ons/front_ma�er/books/
AUCRJ311.13.1/sec�ons/front_ma�er/books/AUCRJ311.13.1/s
ec�ons/front_ma�er/books/AUCRJ311.13.1/sec�ons/front_ma
�er/books/AUCRJ311.13.1/sec�ons/front_ma�er/books/AUCR
J311.13.1/sec�ons/front_ma�er/books/AUCRJ311.13.1/sec�on
s/front_ma�er/books/AUCRJ311.13.1/sec�ons/front_ma�er/bo

oks/AUCRJ311.13.1/sec�ons/front_ma�er#)
An individual characteris�c in an item of footwear, a �re, or ot
her object that occurs as the result of wear and exposure, and th
at can be detected in an imprint or indenta�on of the item.
Analysis, Comparison, Evalua�on, and Verica�on (ACE‐V)
The process followed by fingerprint examiners in their comparis
ons of known and ques�oned fingerprints, as well as foot or pal
m prints.
biometric

Literally, any biological feature that might be used to dis�nguis
h people. Fingerprints are an example of a biometric iden�fier.
bitemark
A mark made in a so� receiving surface by human teeth. Human
teeth, and thus the mark pa�erns they make, are believed to ha
ve individual characteris�cs.
direct physical match

A physical match of pieces of a randomly fractured solid materi
al, such as glass or plas�c, in the manner of a jigsaw fit.
exclusion

A conclusion by an examiner that a ques�oned specimen cannot
have originated from a known specimen with which it has been
compared.
iden�fica�on
In pa�ern evidence comparisons, this term means individualiza
�on, a conclusion that the ques�oned specimen originated from
the known with which it was compared.
impression
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t_matter/books/AUCRJ311.13.1/sections/front_matter/books/AU
CRJ311.13.1/sections/front_matter/books/AUCRJ311.13.1/secti
ons/front_matter/books/AUCRJ311.13.1/sections/front_matter/b
ooks/AUCRJ311.13.1/sections/front_matter/books/AUCRJ311.1
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atter/books/AUCRJ311.13.1/sections/front_matter/books/AUCR
J311.13.1/sections/front_matter/books/AUCRJ311.13.1/sections
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s/AUCRJ311.13.1/sections/front_matter/books/AUCRJ311.13.1/
sections/front_matter#

Any mark made by an object impressing its shape and form into
or onto another object or surface. Impressions can be imprints o
r indenta�ons.

imprint
An effec�vely "two‐dimensional" impression.
inconclusive

In pa�ern evidence comparisons, this conclusion means that the
re is not sufficient informa�on to draw a definite conclusion; th
at is, we cannot say for sure whether the ques�oned is excluded
or there is an
iden�fica�on.
indenta�on
A three‐dimensional impression.
indirect physical match

A physical match of pieces of a non‐solid item or object that ha
s been cut or torn, or of a solid object that fractures in such a w
ay that the pieces cannot be directly realigned.
latent
Literally, "hidden." A latent fingerprint is one that requires proc
essing or development in order to be visible and suitable for co
mparison.

minu�ae
(singular: minu�a) The individualizing characteris�cs of a fing
erprint pa�ern. Primarily, examiners use dots, bifurca�ons, and
ending ridges.
ninhydrin

A chemical that reacts with amino acids to form a visible, violet
‐colored product. It is used to visualize latent fingerprints.
patent
Literally, "visible" or "obvious." A patent fingerprint is visible.
plas�c

An indenta�on fingerprint that has been impressed into a so� r
eceiving surface so as to have depth.
stria�on
A sliding tool mark, resul�ng from one surface sliding on anoth
er and thus crea�ng a mark.
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