The Justice Department adopted a new code of professional responsibility for forensic laboratories on Monday and directed its forensic examiners and prosecutors to avoid overstating their findings in court.
New policies set out in a memo from Attorney General Loretta Lynch include greater transparency and access to forensic laboratory quality assurance documents, which are to be posted online within 18 months.
Last year, the FBI formally acknowledged that, for decades, its forensic examiners gave flawed testimony that overstated the findings from microscopic hair comparisons, including in 32 capital trials that ended in death sentences. Nine of those defendants have been executed.
Under the new policies, forensic examiners and prosecutors are to exercise restraint in presenting their findings, and must abstain from using "reasonable scientific certainty" or "reasonable [forensic discipline] certainty" in reports or testimony.
The department said the changes were recommended by the National Commission of Forensic Science, which advises the Attorney General about how to use forensic evidence.
The policies do not guarantee innocent people access to forensic testing, but the new conduct code is an encouraging step towards more fair and reliable forensic evidence. For example, the code requires forensic examiners to preserve evidence so that independent experts can test it, obligates examiners to "honestly communicate" all information relating to their analyses with defense counsel and other expert witnesses, and prohibits altering findings or withholding information "for strategic or tactical advantage."