Introduction to Presenting Cases Involving DNA

Cases involving DNA evidence are complex in preparation as well as presentation. Prosecutors must diligently work with the state's DNA analyst to prepare for all evidentiary phases of the case. Ultimately, it is the prosecutor's responsibility to insure the DNA analyst communicates the relevant information clearly to the jury and is prepared for potential issues in cross-examination. Making the scientific evidence understandable to the jury can be challenging, and may require limiting the amount of scientific detail presented. Prosecutors should also be aware of statutes of limitations and issues of admissibility.

It is important to show the jury that DNA can do more than identify a person; it can also corroborate the prosecution's theory of a case. The closing argument is a prosecutor's last opportunity to summarize the lab results and remind the jury of the connection between the DNA evidence, the crime charged, and the defendant.

When a prosecutor begins to develop a theory of a case involving DNA evidence, certain questions should be considered:

• How does the DNA evidence support the case theory?
• What must necessarily be true for the DNA evidence to have been recovered where and when it was ultimately recovered?
• How did the evidence come to be located where it was found?
• What other evidence does the DNA evidence corroborate?  
• What else does the location of a person or an item containing DNA evidence reveal about what occurred?
• Alternatively, what does its absence reveal?
• Is its presence or absence consistent with the crime description or narrative of events of a fact witness?

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