Use of forensic methods under exigent circumstances without full validation.

Forensic science can be instrumental in providing investigative leads or clues to help identify the perpetrators, and those who are innocent, of a chemical, biological, radiological, or nuclear terrorist attack, as well as identify leads during infectious outbreaks or other public health threats. Because of a need to react quickly in exigent circumstances during which the threat of continued attack persists, methods may be used that are not fully validated. A preliminary validation should be performed to evaluate the acquisition of limited test data to ensure that the interpretation of results remains within the limitations of known performance of the method. If results from a preliminarily validated method are used beyond developing an investigative lead, further validation should be considered to support its reliability for adjudication purposes.