Breaking NEWz you can UzE...
compiled by Jon Stimac
Experts: Prints Matched Those of Accused
NEW STRAITS TIMES,
MALAYSIA Jun 27, 2006 ...two fingerprint experts confirmed
that the right palm print lifted from the box...
Fingerprints Might be Required to Pawn
NEWS 14 CHARLOTTE, NC
- Jun 26, 2006
...proposed ordinance would require pawnshop owners to
get a fingerprint on each pawn ticket...
Cold Case Unit Charges Suspect in 2 Murders
AUSTIN AMERICAN-STATESMAN, TX
- Jun 26, 2006 ...detectives have arrested
and charged a suspect in connection with the 1984 murder...
Fingerprint Experts Battle it Out Over Disputed McKie Case Evidence
UK - Jun 27, 2006 ...MSPs were faced with radically
different accounts as rival experts lined up to defend their
Recent CLPEX Posting Activity
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Boston Mariott Copley Place - Internet
Steve Everist Sat Jul 01, 2006 11:13 pm
Let's talk about this...
nigeus lowlef Sat Jul 01, 2006 5:13 pm
Latent Print Examiner study at IAI
John Vanderkolk Fri Jun 30, 2006 6:50 pm
One Discrepancy Rule
Michele Triplett Fri Jun 30, 2006 12:46 pm
Bloody Prints on Cloth
jlramirez Thu Jun 29, 2006 7:38 pm
Experiment for Latent Print Examiners (& Trainees) at IA
g. Thu Jun 29, 2006 7:00 pm
ASCLD/LAB accredited Crime Scene Response Units?
Printz S. AndtheP Thu Jun 29, 2006 3:52 pm
Reference: "Development of dermal ridges in the fetus&q
Shaheen Thu Jun 29, 2006 3:23 am
charlton97 Wed Jun 28, 2006 6:30 am
Myths & Truths
Dwayne Dibley Mon Jun 26, 2006 9:51 pm
UPDATES ON CLPEX.com
No major updates this week
we looked at the "One Dissimilarity
Doctrine" from a CLPEX.com forum discussion.
we look at an article critical of AFIS
technology and fingerprint identification.
Cautionary Note About Fingerprint Analysis and Reliance on Digital
by Michael Cherry and Edward Imwinkelried
JUDICATURE Volume 89, Number 6 May-June 2006
Despite the advantages of digital fingerprint technology, its limitations
must be considered.
Every day, the Federal Bureau of Investigation's Integrated Automated
Fingerprint Information System (IAFIS) and its regional Automated
Fingerprint Identification Systems (AFIS) run approximately 130,000 criminal
and employee background checks using digital fingerprint images.
Since March 2005, Homeland Security's US-Visit has conducted fingerprint
searches for over 40 million individuals to determine whether the person who
arrived on U.S. soil is the same person who earlier cleared overseas
departure and whether the person is on the Department's "Watch List."
Given the limited number of trained, competent fingerprint examiners, these
comparisons would not be possible without computers to sort millions of
digital fingerprint images on file and determine whether two images should
be attributed to the same person. But the use of computers to compare
fingerprints raises a host of new issues to consider - issues that, if
unaddressed, will become serious problems.
In an article published in the May/June issue of JUDICATURE, the official
magazine of the American Judicature Society, authors Michael Cherry,
president of Cherry Biometrics, and Edward Imwinkelried, Edward L. Barrett,
Jr., Professor of Law at the University of California, Davis, remind
immigration and terrorism experts, law enforcement and the courts that
digital fingerprint images are "simple, incomplete approximations of the
images they attempt to capture," and that "there are no objective criteria
for determining whether two fingerprint impressions 'match.'"
Today the public is acutely aware of the importance of forensic science. Our
morning papers regularly carry stories about the role of DNA evidence in
both convicting the guilty and exonerating the wrongfully convicted. At
night, the popular CSI television programs dramatize the role that forensic
experts play in criminal investigations.
Although DNA evidence now attracts the greatest attention, for decades
fingerprint analysis was the gold standard in forensic analysis. In
fingerprint analysis, an examiner compares two images or representations of
the friction ridge patterns on fingers. In the past, in criminal cases, one
of the two images, often referred to as the “rolled” image, was typically
produced when a person was arrested. As part of the booking process, the
police rolled the arrestee’s fingertips in ink and then impressed them on a
card. The card was subsequently stored in libraries of such cards maintained
by local, state, and national government agencies. The data on the cards was
classified on the basis of the type of ridge pattern.
The other image, usually termed the “latent,” is typically produced at a
crime scene. If the police suspect that a criminal might have left a
fingerprint impression on a particular surface, such as a glass tabletop,
they can use techniques such as the application of special powders to
visualize the image. When they find an image, they photograph it for
comparison with the images in the library of fingerprint cards.
Again, in the old days, the police used conventional analog cameras and
traditional chemical film to take the photographs. If those administering
the library could classify the type of skin pattern displayed on the latent,
they searched the library for cards of inked images with similar patterns.
An examiner then compared the image of the latent to the fingerprint cards
with the most similar patterns. Based on that comparison, the examiner might
attribute the latent image and the image on a card to the same person. The
fingerprint examiner frequently testified about the comparison at trial.
Thus, in the days of yore, living, breathing fingerprint examiners compared
the images. Several aspects of that paradigm inspired confidence. To begin
with, a human being made a meticulous comparison of the inked and latent
impressions. Moreover, that person was working with the best possible
images. Admittedly, no image perfectly captures a person’s fingerprint
pattern, but some are more complete and therefore more reliable than others.
For the most part, today, that paradigm is passe. We will not and should not
return to the days of yore; but, as we shall see, we need to be far more
aware of the pitfalls lurking in the new paradigm.
Computerized fingerprint analysis
To understand the profound differences between the old paradigm and the new
reality, we must focus on two questions: who and what. Who conducts the
analysis, and what is being analyzed?
Who conducts the analysis—a human being or a computer? During any given year
today, government and business must conduct a huge number of fingerprint
comparisons. Unfortunately, there are not enough examiners to conduct or
verify even 10 percent of the fingerprint analyses that must be completed
annually. Assume hypothetically that you have
1,000 experienced, certified examiners who do nothing but fingerprint
analysis. If those examiners conduct 20 comparisons a day for 365 days, they
will complete only 7,300,000 analyses per year. That number pales in
comparison with the number of analyses that must be conducted.
One government agency alone, Homeland Security’s US-Visit, has conducted
fingerprint searches for over 40 million individuals since March 2005.
US-Visit conducts these searches in order to determine (1) whether the
arrivee on American soil is the same person who earlier cleared the overseas
departure customs and (2) whether that person is on the Watch List.
However, US-Visit is only part of the story. The FBI’s Integrated Automated
Fingerprint Information System (IAFIS) is another important piece of the
picture. On a daily basis, approximately 130,000 employment background and
criminal checks are completed by using IAFIS and its regional Automated
Fingerprint Identification System (AFIS) counterparts. During the course
of a year, those checks could total over 40 million comparisons. Given the
limited number of examiners in the United States, computers have to be
routinely used to conduct the comparisons and determine whether two images
should be attributed to the same person.
The FBI’s IAFIS computerized fingerprint matcher was originally developed by
Lockheed Corporation in the 1990s. In addition, many firms offer combination
fingerprint scanning and enhancement systems that are the building blocks of
our local and regional AFIS systems.
The U.S. Department of Commerce National Institute of Standards and
Technology (NIST) is and has been the primary source for DOJ and Homeland’s
large scale testing of fingerprint matchers. NIST tests these proprietary
matchers for speed and accuracy. The tests have shown instances where the
matchers find more minutia matches than a human examiner could. NIST is
currently contemplating testing the use of fingerprint matchers with latent
It is conceivable that NIST latent fingerprint testing could reveal that
some of the popular matchers that are capable of matching single and
multiple fingerprints lack the appropriate algorithms to accurately match
latent (partial) fingerprints. This would present a problem, since
fingerprint experts have been using the untested matchers with latent
fingerprints to provide them with suspects.
To be sure, in civil settings a computerized match frequently enjoys a major
advantage over the analysis in a criminal case. In many criminal cases, the
comparison is often between a solitary latent image and a ten-print card. In
contrast, in civil cases the comparison is frequently made between two
ten-print cards, decreasing the probability of a misidentification. However,
even in a given civil case that advantage could be absent. The question thus
arises in both civil and criminal cases: In general, does the cost/benefit
analysis favor computerizing fingerprint analysis?
A major benefit of computerization is efficiency. Computerization enables
the examiner to perform identification tasks that were virtually impossible
under the old paradigm. For example, as previously stated, FBI certified
matchers can often find more matches than human examiners.
But there is a price, and here is an example. In a recent interview, Thomas
Bush III, the Assistant Director of Criminal Justice Information Services at
the FBI, conceded that the FBI’s system had missed a fingerprint attribution
for Jeremy B. Jones on three occasions. Jones was a serial killer who was
repeatedly released from custody. Even though the IAFIS library had included
images of Jones’ fingerprint patterns, the computer system failed to “match”
those images to the new images produced each time Jones was re-arrested.
While acknowledging the repeated failures in the Jones case, Mr. Bush noted
that “…. Integrated Automated Fingerprint Information System [is] more than
98 percent accurate and a vast improvement over manually matching
fingerprint cards, a process that used to take 15 to 25 days.” Although
the time saving is desirable and the 98 percent figure is impressive if it
is true, even the 2 percent error figure is distressing. If a computerized
system is involved in 40 million comparisons a year, a “mere” 2 percent
error rate converts into 800,000 erroneous conclusions.
It is no surprise that there is a 2 percent error rate. No system, including
human comparison, is foolproof, but IAFIS takes shortcuts in order to effect
the time saving. For example, even when all 10 fingers of a suspect are
available, in the early prescreening step IAFIS analyzes only the index
fingers. If the prescreening yields a very low score, a non-match decision
is made without analyzing the images of the other fingers. As a result,
the system can fail to identify the person who is the source of the
fingerprint patterns that produced the latent image. The Jeremy Jones
debacle may have been caused by this deficiency in the process.
What is analyzed? The who question is only part of the problem; another key
question is what is analyzed. Again, in the days of yore fingerprint
examiners worked with the best possible images, such as the original inked
exemplars and the original film photographs of the latent crime scene
impressions. Today the original inked exemplars are digital, and the latent
crime scene impressions could also be digital. The latent crime scene
impressions have to be digitized to produce suspects. Once digitized,
fingerprints are run through IAFIS or a regional Automated Fingerprint
Information System (AFIS). The law enforcement community is making extensive
use of digitized technology in its fingerprint systems. In many cases, if
the police succeed in visualizing a latent print at the crime scene, they
use a digital camera to preserve the image. And we must never assume that
once a person is taken into custody a traditional inked exemplar will be
taken. In almost all cases, rather than preparing and preserving an
old-fashioned inked fingerprint card, the police now employ digital
scanners. The suspect places his or her fingers directly on the instrument’s
screen, and the instrument scans the fingers to produce a digital image that
can be printed out later. In subsequent litigation, an inked fingerprint
card will be unavailable because one was never created.
Litigants are not the only persons who might mistakenly assume that they are
dealing with the best possible images of the fingerprint patterns. If an
image has been digitized, it can of course be printed out. Even a
fingerprint examiner might conduct an analysis without realizing that he or
she was working with a digital image.
It is almost impossible to differentiate between traditional inked
fingerprint cards and cards produced by the best available printers.
Simply stated, the reality is that digital evidence is the new paradigm. But
what difference does it make? Although digital photography is in widespread
use, it has its limitations. Digitized images are incomplete. Digitized
fingerprint impressions included in databases are represented by only 500 by
500 pixels per inch out of a minimum 6,000 by 6,000 pixels. In contrast,
conventional 35 mm black and white forensic film employs at least 6,000
pixels per inch (ppi).
Digital printers and screen displays use interpolation techniques to
approximate the appearance of images with 6,000 by 6,000 pixels.
Interpolation is unnecessary when a computer is comparing two images; a
computer does not need to “view” an image in order to compare it. In
contrast, a human examiner does have to view images to compare them, and
that almost always results in interpolated views. Computer experts realize
that the final product of digital photography is not a complete, detailed
reproduction of a 6,000 by 6,000 image; rather, it is an
approximation—nothing less but nothing more.
It is true that database fingerprints of 500 x 500 ppi are thought by some
to contain sufficient information to identify each row and valley of a full
fingerprint. However, images of latent fingerprints are frequently captured
with more detail such as 1,000 x 1,000. Often latent fingerprints of 1,000 x
1000 are matched against AFIS exemplar fingerprints that are 500 x 500. The
detail missing from the 500 x 500 image might be the very detail that
establishes that there is no match between the two images. In short, the
incomplete detail introduces a possibility of error.
The concern is especially acute when the image is of a narrow finger. The
NIST test entitled Pact2002.pdf, using 500 ppi, shows that wider fingers
tend to yield more accurate readings than narrower ones. Wider fingers
touch more of the available sensors and leave more data or dots in a 500 ppi
To appreciate the significance of the number of dots, consider employing
dots to represent numbers. Suppose that we want to represent two numbers,
one and seven. If we use only three dots to represent the numbers, the
representative images will be ambiguous; it will be difficult to distinguish
between the two numbers. Similarly, when we use only 500 dots rather than
6,000 to represent a fingerprint pattern, there can be ambiguity since 6,000
dots are needed to depict a continuous line. By reducing detail, digital
systems increase the likelihood that the database will include “matching”
images for two or more different individuals.
The Mayfield incident
After the March 2004 terrorist attack on Madrid commuter trains, partial
latent prints were discovered and lifted from plastic bags that had
contained detonator caps. Spanish law enforcement authorities sent digital
images of the latents to the FBI for analysis. According to the FBI
statement issued on May 24, 2004, the submitted images were searched through
IAFIS. FBI examiners initially concluded that the latents belonged to
Brandon Mayfield. However, Mayfield was finally released after Spanish
officials conceded that the fingerprints on a bag left near the Madrid
bombing site were not his. The FBI later acknowledged its mistake and at
first explained that, in part, the misidentification was caused by reliance
on “an image of substandard quality,” that is, the digital image.
The later Stacey report stated that the quality of the digital image did not
contribute to the misattribution. The panel concluded that the primary
causes of the misidentification were the extreme pressure of such a high
profile case and the subtle bias created by the realization that other
examiners had already found a match.
Ken Moses, a respected fingerprint expert, and several highly regarded FBI
examiners acknowledged their error in misidentifying Brandon Mayfield as the
Madrid Bomber. A computer imaging expert might consider a different type of
explanation: important details can be lost or distorted when the wrong
settings, components, or combinations of both are used to display images.
Proper alignment is a complex topic. One example is the number of times in a
second that the computer screen is illuminated. The higher the setting the
better the image. Inferior displays are a second example. Better quality
displays are sharper and more accurate as the phosphor dots or LCD cells of
the same color are closer together rather than farther apart.
“Chain of custody”
The use of digital technology in fingerprint analysis is the microcosm.
However, there are broader concerns about reliance on such technology. When
we use our personal digital cameras, the technology seems simple in the
extreme. However, as in many forensic contexts, computerized analysis of
digital fingerprint images to identify a culprit is a multi-step process,
and there is a possibility of error at every step. For instance, there are
potential weaknesses at the following, major steps.
Initially scanning the image into the system. The original latent or
exemplar fingerprint image must first be scanned into the computer. This
raises an input problem. Even the best modern scanners are not accurate
enough to perfectly represent the images they are tasked to scan. (If they
were, we all could have Rembrandts in our living rooms.) In roughly 90
percent of the country, LiveScan scanners have replaced inked-paper based
fingerprint images. Often there are two available settings on LiveScan: 500
dots per inch (dpi) and 1,000 dpi. If the operator chooses the first
setting, the scanned images can omit a critical detail.
Image clean-up (enhancement). Even in this early stage of the conversion
process, it is not uncommon to have a computer operator “clean up” the
scanned image. The operator may exercise subjective judgment in deciding to
delete certain pixels. If there is a later enhancement, the image has been
altered not once, but twice.
Indexing the stored image. Before the image is stored, in many cases it must
be linked (indexed) to a specific person. Some banking and manufacturing
systems automate this step by the use of magnetic ink (MICR) or bar codes,
but others do not. Many public sector systems still rely on fallible human
beings to perform the indexing. In an Oregon case, authorities had assigned
the same electronic fingerprint number to a killer and Miguel Espinoza, a
law-abiding, successful restauranteur in Medford. As a result of the error,
Mr. Espinoza’s liquor license was revoked; and his business was virtually
Storing the scanned image. The indexed, scanned image must be stored for
subsequent retrieval. The image might be stored on a standard hard drive.
However, computer hard drives are vulnerable to hacking, substituting
incorrect information for the correct data. Given the potentially dire
consequences of hacking, each data center should be prepared to detect the
creation of erroneous information and restore the correct information.
However, even some of the largest private companies do not yet have that
technical capability. Similarly, many criminal justice data centers
currently lack that capability.
Retrieving the stored image. Once stored, images can be retrieved or
printed. However, do not assume that the printout is identical to the
original image. Most printers operate on a “best fit” principle. They
sometimes distort the printout of the image in order to avoid black margins
on the printout.
As the preceding discussion indicates, when a film image undergoes the
process of conversion into a digital one, the process may result in
alteration of the image. Some of those changes are inadvertent. However,
there is also the possibility of deliberate manipulation of the image.
Digital enhancement amounts to deliberate manipulation. Image enhancement
technology was developed during the late 1960s and early 1970s for NASA. Due
to the weight and power limitations of spacecraft, it was impractical for
NASA to use state-of-the-art cameras on spacecraft. The cameras used
produced somewhat degraded photographs.
One type of image enhancement reverses the degradation. Initially,
researchers studied the degradation properties of the use of a particular
type of photographic equipment to capture a certain type of image: When this
type of camera is used to photograph distant objects, what type of
degradation can be anticipated? Next, the researchers designed computer
software to compensate for the specific type of foreseeable degradation. The
software improves the sharpness and image contrast of the photograph by
eliminating background patterns and colors.
Before the image on a normal 35 mm photograph can be enhanced, the
photographic image must be digitized. Digital images are composed of
millions of tiny dots, referred to as “pixels.” Based on degradation models
developed in research, computer software manipulates the pixels to filter
out graininess and improve brightness and contrast. Although image
enhancement technology was developed for the space program, the technology
now has a wide variety of applications. The technology has been applied in
numerous areas, including medicine, physics, meteorology, resource
exploration, factory automation, and robotics control. For instance,
forensic scientists utilize the technology to enhance photographs of finger
and palm prints.
In order to “enhance” the image, the computer uses mathematical transforms,
that is, formulae which dictate the alteration of the image. The accuracy of
the enhancement depends on the validity of these formulae. If the formula is
“junk science,” the “enhanced” image will be distorted. A purportedly
enhanced image should not be accepted at face value. Rather, the decision
maker should demand a showing of the validity of the mathematical transforms
programmed into the enhancement software. Unfortunately, if the transforms
introduce distortions into the image, the distortions can be terribly
difficult to detect. A 500 x 500 fingerprint image consists of 25,000
discrete points. Imagine how difficult it would be to detect that the
enhancement program has altered 7 of the 25,000 points.
The focus of this article has been the extensive reliance on computerization
and digital technology in fingerprint analysis. Two caveats are necessary.
First, we are not proposing that we return to the days of yore. Again, there
are significant advantages to computerization.
Secondly, this article is not intended to suggest that all questions about
the reliability of a fingerprint analysis evaporate when a live fingerprint
examiner conducts an analysis of traditional film images of fingerprint
impressions. Some critics have sharply criticized fingerprint analysis on
the ground that there are no objective criteria for determining whether two
fingerprint impressions “match.” In his initial decision in United
States v. Llera Plaza, Judge Milton Pollak took that criticism so
seriously that he ruled that fingerprint examiners may not opine on the
ultimate question of whether both impressions can be attributed to the same
person; the experts would be confined to noting points of similarity between
the two images. Admittedly, in his later decision, Judge Pollak did an about
face; but even in his second opinion he indicated that fingerprint analysis
does not qualify as full-fledged science.
The point of this article is that a further set of troublesome problems is
triggered when a live examiner relies on a less detailed digital image that
may also be interpolated instead of a traditional analog photograph. Until
recently, society, including the public sector, has readily accepted
computerized fingerprint analysis, including reliance on digitized images of
fingerprint patterns. This article has demonstrated that greater skepticism
is warranted. The bottomline is that digital images are simple, incomplete
approximations of the images they attempt to capture.
There are hopeful signs that government agencies and courts are beginning to
take a more critical attitude toward this technology. To its credit,
US-Visit is leading the way. USVisit is now using two exemplar fingerprints
as well as a photograph to verify the identity of arrivees in the United
States; and in close cases, it is having human examiners check the
identification. In the near future, the agency may further upgrade its
system to require a match of all 10 fingerprint patterns. For their part,
some courts are demanding more persuasive showings of the reliability of
digital evidence. Perhaps coincidentally, in May 2004—the very same month as
the Mayfield incident—the Connecticut Supreme Court announced that in the
future Connecticut courts would insist on a more extensive evidentiary
foundation as a condition for accepting digital images.
MICHAEL CHERRY, president of Cherry Biometrics, designs identification
systems. He is Vice Chair, Digital Technology
Committee, National Association of Criminal Defense Lawyers (NACDL). (firstname.lastname@example.org)
EDWARD IMWINKELRIED is the Edward L. Barrett, Jr. Professor at the
University of California, Davis, School of Law.
Editor’s note: The authors would like to thank Jack King for reviewing the
article. Pictures can be viewed at www.cherrybiometrics.com/Images.html
1. NISTIR 7242 Summary of April 2005 ANSI/NIST Fingerprint Standard Update
2. Shaila Dewan, F.B.I. Apologizes for Failing to Identify Murder Suspect,
New York Times, May 5, 2005. www.nytimes.com/2005/05/05/national/05suspect.html?pagew.
5. 35 mm forensic film uses approximately 9600 dots per inch to represent a
7. NISTAPP_Nov02.pdf pages 11,12.
8. Paul C. Giannelli & Edward J. Imwinkelried, Scientific Evidence § 16-4,
at 238 (Supp. 2005) (quoting the May 24, 2004 FBI statement).
9. Robert B. Stacey, Report on the Erroneous Fingerprint Individualization
in the Madrid Train Bombing Case, 54 J. FORENSIC INDENTIFICATION 706
12. Robert Epstein, Fingerprints Meet Daubert: The Myth of Fingerprint
“Science” Is Revealed, 75 S. CAL. L. REV. 605 (2002)).
13. 179 F.Supp.2d 492 (E.D.Pa. 2002).
14. 188 F.Supp. 549 (E.D.Pa. 2002).
15. State v. Swinton, 268 Conn. 781, 847 A.2d 921 (2004); Reni Gertner,
Computer-Enhanced Evidence Requires Detailed Foundation, Lawyers Weekly USA,
June 7, 2004, at 1, 16.
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