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DNA - A Prosecutor’s Practice Notebook Inventory

Expert Witnesses

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Photo of a an expert witness being questioned by a female attorney on a courtroom stand.
National Institute of Justice (NIJ) (see reuse policy).

The prosecution should continue to consult with its own DNA analyst during the course of the trial. Since the analyst testifying as an opinion witness is not bound by the same rules of sequestration as fact witnesses, if possible, prosecutors should have the DNA analyst sit in during the course of the defense expert's testimony for advice on countering the defense arguments. Prosecutors should freely consult with the state's DNA analyst during the presentation of the defense case to determine whether expert rebuttal testimony is warranted.

The overriding principle of cross-examination is to keep it simple. Prosecutors need to ask only leading questions to pin down the defense experts and prevent them from having free reign to discuss their theories on the stand. Prosecutors should use only simple, not compound, questions to limit the scope of the expert's testimony. Finally, they ought to ask the court to control a "runaway" expert whose testimony cannot be otherwise limited.

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