Rule 702 of Article VII of the Federal Criminal Code and Rules states that “If scientific, technical or other specialized knowledge will assist the trier of fact to understand the evidence or to determine a fact in issue, a witness qualified as an expert by knowledge, skill, experience, training, or education, may testify thereto in the form of an opinion or otherwise”. 1 State and local courts in the U.S., as well as most courts in the world, have similar guidelines allowing the opinion testimony by a qualified expert witness.