NEW YORK — FBI agents in every region of the country have mishandled, mislabeled, and lost evidence, according to a highly critical internal investigation that discovered errors with nearly half the pieces of evidence it reviewed.
The evidence collection and retention system is the backbone of the FBI’s investigative process, which the report said it is beset by problems. It also found that the FBI was storing more weapons, less money and valuables, and 2 tons more of drugs than its records had indicated.
The report’s findings, based on a review of more than 41,000 pieces of evidence in FBI offices around the country, could affect criminal investigations and prosecutions. Lawyers can use even minor record-keeping discrepancies to get evidence thrown out of court, and the FBI was alerting prosecutors Friday that they may need to disclose the errors to defendants.
Many of the problems cited in the report appear to be hiccups in the FBI’s transition to a computer system known as Sentinel, which went online in 2012 and was intended to replace a system based on paper files. Other problems, including materials that disappeared or were taken from evidence rooms and not returned, are more serious.
“A majority of the errors identified were due in large part to human error, attributable to a lack of training and program management oversight,” auditors wrote in the report, which was obtained by The New York Times.
The bureau issued a statement saying the review had “yielded several valuable proposals to increase the effectiveness and efficiency of the FBI’s corporate tracking system for evidence, and the FBI is currently in the process of implementing same.”
The FBI is separately dealing with the fallout from a case at its Washington office, where an agent is under investigation for tampering with evidence. That has led to the dismissal of convictions in some drug cases.
Although the internal review is unrelated to that matter, the issues are so entwined that the FBI plans to distribute the report to dozens of lawyers involved whose cases were affected by the Washington office, officials said.
The errors cited in the audit range in severity from computer glitches and duplicate bar codes to evidence that could not be located.
The investigation found that federal agents had removed 1,600 pieces of evidence from storage and had not returned them for more than four months. One piece of evidence in a drug case has been signed out since 2003.
Because the audit was based on a sample, the actual number of items that have been checked out and not returned is probably higher.
Meanwhile, a separate report found that the FBI used flawed scientific methods to investigate the 2001 anthrax attacks that killed five people and sickened 17 others, federal auditors said Friday. The report will fuel skepticism over the FBI’s conclusion that Army researcher Bruce Ivins was the sole perpetrator.
The 77-page report from the Government Accountability Office says the FBI’s research, including novel microbial forensic tests, did not provide a full understanding of how bacteria change in their natural environment and in a laboratory.
This failure to grasp the reason for genetic mutations that were used to differentiate between samples of anthrax bacteria was a ‘‘key scientific gap’’ in the investigation, the report says.
The GAO also found a lack of rigorous controls over sampling procedures and a failure to cite the degree of uncertainty in measurement tools used to identify genetic markers.
The GAO didn’t take a position whether Ivins, who worked at Fort Detrick in Maryland, made and mailed the anthrax-filled envelopes.
This is the second government report to find fault with the FBI’s methods. The National Research Council said in 2011 that federal investigators overstated the scientific case against Ivins but that the evidence was consistent with the FBI’s conclusions.
The new report doesn’t shake the FBI’s confidence in its decision to formally close in early 2010 the investigation it dubbed Amerithrax, spokesman Christopher Allen said.
‘‘Our conclusions weren’t based solely on the science but the full evidence before us,’’ he wrote in an e-mail. Investigators have acknowledged that the evidence is circumstantial.
The FBI said in a written response to the report that in the past decade it has helped develop a national microbial forensics laboratory to conduct ‘‘validated and accredited’’ investigations.
Ivins died in July 2008 of an apparently intentional Tylenol overdose as the Justice Department prepared to indict him for the attacks. He had denied involvement, and his lawyer and some colleagues said he was hounded to self-destruction.
Material from the Associated Press was used in this report.