Transcript The Detection of Latent Fingermarks on Porous Surfaces


Composition differs between individuals
› Age, health, diet, medication

Ninhydrin reacts with amino acids found
in sweat
› Dependent on pressure, contact time &
quantity
 High
variability, low certainty
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Ninhydrin
› Complete degradation after 60 minutes
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DFO
› Complete deterioration after 3 hours

Indanedione
› 80% degradation after 60 minutes
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Amino Acids are water soluble
› DFO & Ninhydrin cannot be used on surfaces
that have been exposed to high moisture
ESDA Processing and Latent Fingerprint Development: The Humidity Effect
Myriam Azoury M.Sc. ; Rachel Gabbay M.Sc. ; Drorit Cohen B.A. ; Joseph Almog Ph.D.
Journal of Forensic Sciences Volume:48 Issue:3 Dated:May 2003 Pages:564 to 580
“Fingermark detection techniques have
been developed from the knowledge of
the components of human skin
secretions, without regard to the
potential for aging of the print.” (p. 129)

Squalene
› Naturally produced lipid found in fingerprints
› Highly unsaturated, relatively quick oxidation
rate
› Complete degradation after 9 days
Nia E. Archer, Yannis Charles, Julia A. Elliott, Sue Jickells,
Changes in the lipid composition of latent fingerprint residue with time after deposition on a surface, Forensic Science International,
Volume 154, Issues 2–3, 25 November 2005, Pages 224-239, ISSN 0379-0738, 10.1016/j.forsciint.2004.09.120.
No current standard protocol between
crime labs
 Unique environments lead to difficulty in
distinguishing between prints with a set
degree of certainty

Fingerprinting: non-scientific
expert evidence
 No known or recognized error rate

› Claimed to be zero
Latent prints typically partial, smudged or
otherwise distorted
 No qualifications required to be
considered an expert in latent print
examination
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http://cdn-wac.emirates247.com/polopoly_fs/1.285933.1283242587!/image/1491345025.gif
“I’ll preach fingerprints till I die. They’re
infallible.”
- Massey, FBI Fingerprint Examiner
Mayfield Case
“Fingerprints are absolute and infallible.”
- FBI Fingerprint Examiner

Proficiency test for latent fingerprint
identification
› Collaborative Testing Service
› International Association for Identification
Four suspect cards with all ten prints and
seven latent prints given to subjects
 156 people took the test, 68 (44%)
correctly classified all seven latent prints
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MEAGHER: The latent print is, in fact, identical with the known exemplar.
STAHL: It’s identical?
MEAGHER: Yes.
STAHL: You can tell that?
MEAGHER: Yes.
STAHL: What are the chances that it’s still not the right person?
MEAGHER: Zero.
STAHL: Zero.
MEAGHER: It’s a positive identification.
Cole, Simon A., More than Zero: Accounting for Error in Latent Fingerprint Identification.
Journal of Criminal Law and Criminology, Vol. 95, No. 3, 2005. Available at SSRN: http://ssrn.com/abstract=1025772
6 ½ years in jail
 1997, Convicted of attempted murder of
a police officer
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› based on fingerprints and eyewitness
testimony
Real culprit never found
 Exonerated by DNA evidence
 Resulted in the entire fingerprint unit of
the Boston Police Department being shut
down

Cole, Simon A., More than Zero: Accounting for Error in Latent Fingerprint Identification.
Journal of Criminal Law and Criminology, Vol. 95, No. 3, 2005. Available at SSRN: http://ssrn.com/abstract=1025772
Lawyer; Portland, Oregon
 Accused of the May 2004 Madrid
Bombings
 2 weeks in police custody
 Print “positively identified” by three
independent highly qualified latent print
examiners as belonging to Mayfield
 Print later determined by Spanish Police
to belong Ouhnane Daoud

Cole, Simon A., More than Zero: Accounting for Error in Latent Fingerprint Identification.
Journal of Criminal Law and Criminology, Vol. 95, No. 3, 2005. Available at SSRN: http://ssrn.com/abstract=1025772
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Recovery of latent fingerprints from skin
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Fingerprint residue composition
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Aging fingerprints
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Understanding of the mechanisms of chemical
reagents under examination conditions
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Without this work, latent fingerprint recovery will
continue to rely on empirical observations and
experience
“We need to acknowledge that latent
print identification is susceptible to error,
like any other method of source
attribution, and begin to confront and
seek to understand its sources of error.”
- Simon Cole, Criminologist,
University of California
Fingerprint evidence is notoriously
unreliable leading to many wrongful
convictions
 Recovery of latent fingerprints is not a
straightforward chemistry problem but is
a complex scenario requiring the
consideration of many interrelated
factors
 Highly variable science, with no standard
sensitivity, error or protocol
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