Expert comparisons of hair, handwriting, marks made by firearms on bullets, and patterns such as bite marks and shoe and tire prints are in some ways unscientific and subject to human bias, a National Academy of Sciences panel chartered by Congress found. Even fingerprint identification is partly a subjective exercise that lacks research into the role of unconscious bias or even its error rate, the panel's 328-page report said. Since 2002, failures have been reported at about 30 federal, state and local crime labs serving the FBI, the Army and eight of the nation's 20 largest cities. A 2009 study of post-conviction DNA exonerations - now up to 289 nationwide - found invalid testimony in more than half the cases. FBI examiners claimed until recently that they can match fingerprints to the exclusion of any other person in the world with 100 percent certainty. The academy report found that assertion was "not scientifically plausible" and had chilled research into error rates. In 1999, a Justice Department official, Richard Rau, told a federal court that the department delayed such a study because of the legal ramifications. Meanwhile, errors occur. In 2004, DNA for the first time exonerated a person convicted with a fingerprint match and, separately, the FBI made its first publicly acknowledged fingerprint misidentification. Brandon Mayfield, a Portland, Ore., lawyer, mistakenly was arrested in connection with the terrorist train bombings in Madrid that killed 191 people.