By Carol Cratty, CNN Senior Producer

updated 9:50 AM EDT, Wed September 26, 2012

STORY HIGHLIGHTS

Washington (CNN) -- The FBI lab has made strides in cutting down its backlog of forensic DNA cases, according to a report released Tuesday by the Justice Department's Office of Inspector General.

As of March 2012 the backlog stood at 403 cases compared to 3,211 cases two years prior.

The report attributed the improvement to increased use of automation, more staff and a focus on using DNA analysis in situations in which it's most likely to yield useful results.

The FBI lab tests biological evidence found at crime scenes and items like envelopes, drinking glasses and articles of clothing. The lab does the work for not just the FBI but also for local police departments that don't have forensic labs.

FBI, Justice Department reviewing forensic evidence in thousands of cases

The report found the biggest reduction in cases came in the area of nuclear DNA, in which biological fluids like blood and semen are analyzed. There was not as large a drop in the backlog of cases involving mitochondrial DNA, which looks at such things as teeth, hair and highly degraded fragments of bones.

According to the inspector general, the FBI decided not to examine samples in 300 of the backlogged mitochondrial DNA cases that came from the FBI's Terrorist Explosive Device Analytical Center. The report said it had been policy to submit all hairs found on improvised explosive devices. "The FBI told us that there have been no documented instances for which probative results were generated from these mitochondrial DNA examinations," said the report. The FBI changed its policy on analyzing samples from all such cases.

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FBI makes headway on DNA testing backlog, report says