I think you are making a great leap of faith here. Even experts cannot say that the defendant's fingerprints were found at the scene of the crime. Fingerprints are invariably smudged and experts usually use a point system to determine a certain number of coinciding features.
However, there are no universal standards of matching points.. "...the FBI has stated that there should be no minimum standard and that the determination of whether there is a sufficient basis for an identification should be left to the subjective judgment of the individual examiner. The same is applied in the United Kingdom. On the contrary, other countries have set standards. For example, Australia has a minimum standard of twelve matching ridge characteristics whereas France and Italy have sixteen."
We need look no further than
the case of Brandon Mayfield who was arrested for terrorism because "A federal judge signed the material witness warrant authorizing Mayfield’s arrest based on a supporting affidavit by FBI agent Richard K. Werder. The affidavit’s lynchpin was the allegation that senior FBI fingerprint examiner Terry Green identified 'in excess of 15 points of identification during his comparison' of Mayfield’s prints on file with the Army and the FBI, and a 'photograph image' of a print recovered from a plastic bag containing several detonators found in a stolen van near where three of the bombed trains departed. 3 The affidavit further alleges that the fingerprint identification was verified by an FBI fingerprint supervisor and a retired FBI fingerprint examiner with 30 years of experience on contract with the lab’s Latent Fingerprint Section."
-----------------------
It sure sounded bad for Brandon. However, he was later exonerated. In fact, he had never travelled to Spain. What was the problem? Why did fingerprint evidence pick him up? I quote:
"How can fingerprint analysis be so unreliable that three FBI experts and an independent analyst could mistake the print of a mild-mannered family man with an expired passport who has never been to Spain, for that of an international terrorist? The answer lies in understanding the foundation of fingerprint theory rests on three assumptions -
two that are scientifically unproven and one that has been empirically disproven....
"The third assumption – that fingerprint examiners have the skill to infallibly determine [whether] print samples from different sources originated from the same person –
has been empirically disproven. The many people falsely implicated in a crime by an erroneous fingerprint ID is
consistent with proficiency tests over the past several decades that have resulted in
failure rates by experienced examiners of over 50%. That lack of expertise is predictable considering fingerprint analysis is an artful technique that depends on a
human interpreter’s subjective evaluation. In 1892, Francis Galton, one of the fathers of fingerprinting, was honest enough to write, “A complex pattern [such as fingerprints] is capable of suggesting various readings, as the figuring on a wallpaper may suggest a variety of forms and faces to those who have such fancies.” 23 One hundred and ten years later Scotland’s Justice Minister echoed Galton’s assessment by
acknowledging fingerprinting “
was not an exact science.” That observation was in response to the
August 2002 reversal of David Asbury’s murder conviction when fingerprint evidence used against him was discredited. The FBI is disingenuous by claiming fingerprinting is scientific, while acknowledging its lab’s dependence on subjective fingerprint examination techniques. The agency claims reliance on “
human experience” and
intuition rather than a rigorous process results in a more accurate analysis."