He has conducted studies that show that when working on an identification, fingerprint examiners can be influenced by what else they know about a case. In one experiment, he found that the same examiner can come to different conclusions about the same fingerprint, if the context is changed over time.

The same kinds of contextual biases arise with other decision-makers, said Dr. Dror, who works with the military and with financial and medical professionals. He thinks one reason forensic examiners often do not acknowledge that they make errors is that in these other fields, the mistakes are obvious. “In forensics, they don’t really see it,” he said. “People go to jail.”

Just as police officers conducting lineups should not be told whether the suspect is or isn't among those who are lining up, forensic scientists who are asked to match a fingerprint shouldn't be told whether the print is suspected to have been left by a particular person. Any other standard raises concerns about the objectivity of the analysis.