The appropriate scope and extent of cross-examination of such experts is dependent on the individual witness. Traditional cross-examination techniques may be most effective. These include the dependency of the expert on income derived from forensic consultation and testimony, as well as the expert's absence of knowledge and experience in forensic DNA typing. Cross-examination of such experts is frequently best devoted to the existence of recent substantial scientific research affirming the validity of the population frequency data calculation procedures employed by DNA typing laboratories. Rebuttal testimony of a disinterested non-forensic DNA scientist may be used to counter defense assertions.
Numerous scientists are available to review laboratory protocols and case-specific data.
The prosecutor may, on rare occasions, be required to cross-examine a defense expert who presents the results of defense DNA testing. The procuring of all data, including reports, bench notes, autoradiographs, written protocols, photographs and related materials in possession of the testing laboratory must precede any such cross-examination. A consulting expert witness should conduct evaluation of any testing results which materially impact the current prosecution. The impact of results of scientific evidence testing which may demonstrate the innocence of a criminal defendant must always be considered and weighed carefully. Effective presentation of DNA evidence at trial will normally resolve questions regarding the identity of depositors of evidentiary biological samples for the trier of fact.