Justice Department officials have known for years that flawed forensic work might have led to the convictions of potentially innocent people, but prosecutors failed to notify defendants or their attorneys even in many cases they knew were troubled.
Officials started reviewing the cases in the 1990s after reports that sloppy work by examiners at the FBI lab was producing unreliable forensic evidence in court trials. Instead of releasing those findings, they made them available only to the prosecutors in the affected cases, according to documents and interviews with dozens of officials.
In addition, the Justice Department reviewed only a limited number of cases and focused on the work of one scientist at the FBI lab, despite warnings that problems were far more widespread and could affect potentially thousands of cases in federal, state and local courts.