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LOUISE: I never would have guessed that he was selling fake insurance.
CANEWELL: That's what the whole idea was ... he didn't want you to guess it. If you could have guessed, then he couldn't have sold nobody no insurance.
- August Wilson, Seven Guitars (1996)
INTRODUCTION
The year 2004 witnessed what was probably the most highly publicized fingerprint error ever exposed: the case of Brandon Mayfield, an Oregon attorney and Muslim convert who was held for two weeks as a material witness in the Madrid bombing of March 11, 2004, a terrorist attack in which 191 people were killed. Mayfield, who claimed not to have left the United States in ten years and did not have a passport, was implicated in this attack almost solely on the basis of a latent fingerprint found on a bag in Madrid containing detonators and explosives in the aftermath of the bombing. Unable to identify the source of the print, the Spanish National Police emailed it to other police agencies. Federal Bureau of Investigation (FBI) Senior Fingerprint Examiner Terry Green identified Mayfield as the source of the latent print.1 Mayfield's print was in the database because of a 1984 arrest for burglary and because of his military service. The government's affidavit stated that Green "considers the match to be a 100% identification" of Mayfield.2 Green's identification was "verified" by Supervisory Fingerprint Specialist Michael Wieners, Unit Chief, Latent Print Unit and fingerprint examiner John T. Massey, a retired FBI fingerprint examiner with over thirty years of experience.
Kenneth Moses, a well-known independent fingerprint examiner widely considered a leader in the profession, subsequently testified in a closed hearing that, although the comparison was "quite difficult," the Madrid print "is the left index finger of Mr. Mayfield."3 A few weeks later the FBI retracted the identification altogether and issued a rare apology to Mayfield.4 The Spanish National Police had attributed the latent print to Ouhnane Daoud, an Algerian national living in Spain.
The error occurred at a time when the accuracy of latent print identification has been subject to intense debate. Because the Mayfield case is the first publicly exposed case of an error committed by an FBI latent print examiner and the examiners were highly qualified, it was particularly sensational.