FBI investigators in a file photo. REUTERS/Phil Klein

WASHINGTON (Reuters) - The FBI’s laboratory has a backlog of more than 3,200 forensic DNA cases, which can prevent timely capture of criminals and prolong incarceration of innocent people, according to a U.S. Justice Department report released on Monday.

The report by the department’s inspector general said the backlog, which has increased sharply in the past year, can cause delays in legal proceedings that must await DNA analysis results.

The DNA evidence typically comes from forensic samples from crime scenes or from such items as clothing, envelopes and drinking glasses.

Of the backlog, more than 2,700 cases are in the laboratory unit that primarily examines biological fluid stains, such as blood and semen. Nearly 500 cases are in the unit that analyzes evidence such as hair, bones, and teeth.

The report said the delays can prolong the incarceration of innocent people who could be exonerated by DNA evidence and can adversely affect families of missing persons waiting for positive identification of remains.

The time it takes to receive the FBI laboratory results varies from about 150 days to more than 600, depending on the type of DNA evidence submitted for analysis.

The FBI has adopted a number of measures in an effort to reduce the backlog and minimize laboratory bottlenecks, the report said.

The FBI is in the process of adding 17 additional forensic examiners, but their hiring and training could take as long as 18 months.

The backlog of cases has been considered a problem for a number a years, as the federal law enforcement agency seeks to come up with an electronic evidence tracking system, according to the report.