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Forensic DNA Education for Law Enforcement Decisionmakers

Handling Cold Hits in the Laboratory

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Handling Cold Hits in the Laboratory

A doctor and child looking at a computer screen
National Institute of Justice (NIJ) (see reuse policy).

For cold hits between an unsolved case and a person convicted of or arrested for an offense, the laboratory working the unsolved case notifies the laboratory that analyzed the sample in the database of the hit, which then warrants follow-up. The laboratory with the database sample then conducts a series of quality control measures designed to minimize the risk that an innocent person will be implicated in a crime. These measures may include reanalysis of the DNA sample or use of other forensic information such as comparison of an inked print or biographical information checks.

Upon completion of the quality control steps, the database sample laboratory will notify the casework laboratory (or law enforcement agency in some jurisdictions) of the person contributing the data sample's identification. Depending on the jurisdiction, this may be sufficient probable cause for arrest.

The FBI encourages collection of a new standard sample from the implicated individual for direct comparison to the evidence. This is an important step, as it provides a sample with proper chain of custody from a properly identified subject. Since the new sample is analyzed in the same laboratory as the casework sample, it avoids potential technical questions that may arise at trial.

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