September 25, 2012, 11:17 AM

The Federal Bureau of Investigation’s crime lab has whittled its backlog of DNA cases down to 403 — from more than 3,200 in 2010, according to a new report by the Justice Department’s watchdog.

The backlog is made up of cases in two separate DNA units: nuclear and mitochondrial.

No, not all DNA analysis is created equal. Nuclear DNA analysis can generate a profile of a single person. But nuclear DNA analysis isn’t always possible. Examinations of highly degraded bone fragments, teeth and hair, for example, lend themselves to mitochondrial DNA analysis. Mitochondrial DNA is maternally inherited, so several people can have the same mitochondrial profile.

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