 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

 Ninhydrin › Complete degradation after 60 minutes  DFO › Complete deterioration after 3 hours  Indanedione › 80% degradation after 60 minutes  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 , ISSN , /j.forsciint

 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

“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

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, Available at SSRN:

 6 ½ years in jail  1997, Convicted of attempted murder of a police officer › 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, Available at SSRN:

 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, Available at SSRN:

 Recovery of latent fingerprints from skin  Fingerprint residue composition  Aging fingerprints  Understanding of the mechanisms of chemical reagents under examination conditions  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