Following are sample direct and cross examinations of experts, most from cases that Sheldon & Flood, PLC have litigated. Before conducting either a direct or cross-examination of an expert witness, the criminal defense attorney must become an expert in the relevant forensic expertise as well as in the basic principals of forensics.
Firearm Tookmark Expert
Summary: The Assistant United States Attorney conducts a direct examination of Forensic Scientist Gary Arntsen to establish that certain shell casings are connected to a shooting scene. The scientist’s qualifications are substantial and uncontested. Of note during the qualification section is that the prosecutor admits into evidence, without objection, the scientist’s curriculum vitae. While technically relevant, some judges may not allow a CV into evidence over objection, particularly when the expert has discussed the vast majority of his or her qualifications already, and when such qualifications are not contested. The scientist discusses how cartridges are compared with known samples fired from a gun, and how a comparison between samples of known and unknown origin can yield the opinion that a particular cartridge was indeed fired from a particular gun.
As to the case at hand, the scientist is able to identify some of the tested cartridges as matching, while others are “inconclusive.” Defense counsel Lana Manitta makes several points on cross-examination, including, but not limited to, that the scientist cannot determine when any particular cartridges were fired, that any particular cartridges were fired on the same day as each other, and whether any of the cartridges actually passed through a person.