IN CONTRAST TO ORDINARY WITNESSES, WHO ARE PRECLUDED FROM AN OPINION ON A MATTER AT ISSUE IN A TRIAL, WITNESSES QUALIFIED BY SOME SPECIAL SKILL, TRAINING, OR EXPERIENCE, CAN BE ASKED FOR OPINIONS ON MATTERS THEY HAVE INVESTIGATED IN THEIR PROFESSIONAL CAPACITY. EXPERTS ARE CALLED BOTH TO PROVIDE BASIC INFORMATION ON TECHNICAL MATTERS AND BECAUSE THE COURT ALONE CANNOT INTERPRET THE TECHNICAL FACTS. THE TRIAL JUDGE DETERMINES WHETHER THE WITNESS QUALIFIES AS AN EXPERT. QUALIFICATIONS MAY INCLUDE WORK HISTORY, EDUCATION, SPECIAL COURSES, AWARDS, SPEECHES OR ARTICLES, TEACHING EXPERIENCES, MEMBERSHIP IN PROFESSIONAL SOCIETIES, PRIOR COURT EXPERIENCE AND QUALIFICATION, AND PRIOR WORK AND TRAINING UNDER RECOGNIZED SPECIALIZED EXPERTS. IN COURT, ATTACKS ON EXPERTS' QUALIFICATIONS ARE BASED ON THE RELATIONSHIP BETWEEN THE MATTER UNDER REVIEW AND THE EXPERT'S WORK HISTORY, EDUCATION, EXPERIENCE, AND TRAINING. USUAL METHODS OF IMPEACHING EXPERT TESTIMONY THROUGH CROSS-EXAMINATION INCLUDE EXPLORING LIMITATIONS OF THE FIELD OF EXPERTISE, ATTACKING CREDENTIALS, ATTACKING THE PHYSICAL SAMPLE'S ADEQUACY OR IDENTITY, USING TEXTS OR TREATISES TO PROVIDE CONTRADICTORY VIEWS, AND QUESTIONING ADEQUACY OF TESTING PROCEDURES ADOPTED. IF A WITNESS USES WRITTEN NOTES, THEY MUST BE PREPARED AT OR NEAR THE TIME WHEN THE MATTERS WERE OBSERVED. NOTES OR DEPOSITIONS MAY USUALLY BE USED DURING THE TRIAL, BUT DENYING THE TRUTH OF PRIOR WRITTEN STATEMENTS WILL JEOPARDIZE THE WITNESS' CREDIBILITY. ADEQUATE COMMUNICATION AND PREPARATION BY BOTH THE EXPERT WITNESS AND COUNSEL ARE ESSENTIAL IF THE TESTIMONY IS TO PROVIDE MAXIMUM BENEFIT. USE OF DEMONSTRATIVE EVIDENCE (MAPS, MODELS, ETC.), AND DETAILED EXPLANATIONS BY EXPERT WITNESSES ALSO ARE RECOMMENDED. FOOTNOTES INCLUDING REFERENCES ARE INCLUDED. (CFW)