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DNA - A Prosecutor’s Practice Notebook Inventory

Obtaining Confirmatory Testing

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Photo of a woman swabbing saliva and obtaining a blood sample from her arm.
National Institute of Justice (NIJ) (see reuse policy).

A CODIS hit may provide probable cause for an arrest. The prosecutor should remember, however, that the CODIS hit is rarely admissible at trial, in part for chain of custody issues.  Additionally, not bringing the cold hit before the jury avoids potential issues regarding databases of convicted persons and corresponding population statistics. 

New or "fresh" reference samples need to be lawfully obtained from the suspect so that confirmatory typing may be done. Most forensic labs have protocols which require a suspect's sample be obtained either by written consent or by warrant or other court order. In many states, a search warrant can only be executed and served within the jurisdiction where the suspect is located. If the suspect resides outside the jurisdiction, the prosecutor may need to assist the lead investigating officer in making certain the warrant is properly executed in the jurisdiction in which the suspect resides.

Once the "fresh reference samples" have been obtained, they, together with the evidence collected (including the victim's standards, where applicable), need to be

transported to the lab for confirmatory typing.  This process can take weeks before the test results and lab reports are finalized.  If the suspect is already in custody on other charges, it is preferable to make the arrest on the new charges and commence the prosecution after the confirmatory typing is completed.  However, if the suspect is at large, an arrest may be needed before the confirmatory typing can begin.  In this case, it is advisable to obtain the suspect's reference samples at or as close to the time of arraignment as possible.

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