When a criminal defendant’s fingerprints are at issue, the stakes are high. The person has been accused of a crime, and those fingerprints could theoretically place them at the crime scene or otherwise indicate their involvement. People go to prison in cases where a matching fingerprint is the primary evidence.
We should expect that the standards for fingerprint analyst would be reasonably high, but The Intercept recently found that those standards are surprisingly low.
In fact, a group of three public defenders from Illinois recently passed the proficiency test without getting any training or special knowledge. Each got 11 out of 12 right, seeming to ace the test with no preparation. Yet real fingerprint analysts use the fact that they’ve passed these proficiency tests as proof that they are experts.
Proficiency tests are widely used as evidence of expertise in the field. According to federal data, 98% of forensic science practitioners who work in accredited public crime labs take these tests. Unfortunately, as these public defenders told The Intercept, many practitioners seem to know very little about their work.
Close non-matches could result in false accusations
It’s not that fingerprint analysis is simple. Mistakes are made, and they can have serious consequences. For example, in the 2004 Madrid train bombing case, authorities identified an Oregon lawyer’s fingerprints as those at the scene.
That lawyer was exonerated. The issue was that the fingerprints found on the scene were a “close non-match” to his. This typically means that investigators have a print from the crime scene with no known match, so they run the print through a database like the FBI’s Automated Fingerprint Identification System, which provides a list of possible suspects. These are typically people with similar, although not necessarily identical, fingerprints.
The problem with close non-matches is that they may not match at all, allowing an innocent person to be accused. The reason they are used, however, is that most crime scene fingerprints are messy — bloody, smudged or partial. The analyst’s job is to show whether a messy crime scene print is the same as a clean print taken for identification purposes.
But the fingerprinting proficiency test didn’t include any messy fingerprints to compare. There were no close non-matches, at all.
Indeed, when the public defenders looked into the proficiency tests, nearly everyone who took it over the last several years seemed to have aced it. Passage rates were routinely in the high 90% range. It seemed either that the test takers were unusually proficient or that the tests were quite easy.
We recommend reading The Intercept’s entire report. In the meantime, juries should not be impressed by the fact that a fingerprint analyst has passed a proficiency test.