If a hearing is granted, the burden of proof lies with the proponent of the evidence. The burden of proof that the proponent must bear is proof by a preponderance of the evidence [Bourjaily v. U.S., 483 U.S. 171; 107 S. Ct. 2775; 97 L. Ed. 2d 144 (1987)]. Prosecutors should note that in states following the Federal Rules of Evidence, the routine rules of evidence do not apply at admissibility hearings. F.R.E. Rule 104(a) (rules governing admissibility).

Even when DNA evidence is admitted, the prosecutor may still face challenges to the interpretation of the typing results. With all DNA typing methods, there are certain artifacts that may occur during the course of the typing. Lab analysts are aware of such artifacts (e.g., pull-up, stutter, etc.) and are adept at identifying them. Lab analysts can explain these anomalies, how they occur, how they are detected, and what effect, if any, they may have on the interpretation of the results.

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