When firearms examiners are called to the witness stand to be qualified as to their expertise, their present occupation, academic and professional background, experience, honors, and publications should be fully developed. Objections to the competency of the witness should be made by voir dire out of the presence of the jury. If the court sustains the objection, the witness will be prohibited from testifying. However, courts are very liberal in receiving qualified witness's testimony, even if it has slight probative value. Successful cross-examination of a firearms witness is based on thorough pretrial preparation, since the witnesses are not required to disclose the underlying data supporting their opinions. Therefore counsel should take the opposing witness's disposition before trial to assure adequate familiarity with the data. Counsel should also consider obtaining advice from a consultant who possesses expertise on the correct and effective methods needed to question an opposing witness. Demonstrative evidence involving firearms is an important aid in simplifying the witness's opinion. After having the physical item properly marked, counsel should lay the foundation for the admission of the physical evidence and have the item properly marked at a pretrial conference to avoid going through the identification process at trial. Counsel should also be prepared to produce proper foundation evidence and be prepared to meet any objection the opposing counsel may make to a particular exhibit. Opposing counsel should be prepared to state any objections to the receipt of the proffered evidence. The objections can be predicated on such grounds as the inability of the witness to swear to the authenticity of the evidence or to locate its source, and because counsel has failed to lay a proper foundation demonstrating that the exhibit could explain a fact important to the inquiry. Three references are included. For related articles, see NCJ 75559-61.