Article VII. Opinions and Expert Testimony

Rule 701. Opinion testimony by lay witnesses.

If the witness is not testifying as an expert, his testimony in the form of opinions or inferences is limited to those opinions or inferences which are 
    (1)  Rationally based on the perception of the witness; and 
    (2)  Helpful to a clear understanding of his testimony or the determination of a fact in issue. 

Rule 702. Testimony by experts.

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. 

Rule 703. Basis of opinion testimony by experts.

The facts or data in the particular case upon which an expert bases an opinion or inference may be those perceived by or made known to him at or before the hearing. If of a type reasonably relied upon by experts in the particular field in forming opinions or inferences upon the subject, the facts or data need not be admissible in evidence. 

Rule 704. Opinion on ultimate issue.

Testimony in the form of an opinion or inference otherwise admissible is not objectionable because it embraces an ultimate issue to be decided by the trier of fact. 

Rule 705. Disclosure of facts or data underlying expert opinion.

The expert may testify in terms of opinion or inference and give his reasons therefor without prior disclosure of the underlying facts or data, unless the court requires otherwise. The expert may in any event be required to disclose the underlying facts or data on cross-examination. 

Rule 706. Court appointed experts.

(a)  Appointment. The court, on motion of any party or its own motion, may enter an order to show cause why expert witnesses should not be appointed, and may request the parties to submit nominations. The court may appoint any expert witnesses of its own selection. An expert witness shall not be appointed by the court unless he consents to act. A witness so appointed shall be informed of his duties by the court in writing, a copy of which shall be filed with the clerk, or at a conference in which the parties shall have opportunity to participate. A witness so appointed shall advise the parties of his findings, if any; his deposition may be taken by any party; and he may be called to testify by the court or any party. He shall be subject to cross-examination by each party, including a party calling him as a witness. 
    (b)  Compensation. Expert witnesses so appointed are entitled to reasonable compensation in whatever sum the court may allow. The compensation thus fixed is payable from funds which may be provided by law in criminal cases and civil actions and proceedings involving just compensation for the taking of property. In other civil actions and proceedings the compensation shall be paid by the parties in such proportion and at such time as the court directs, and thereafter charged in like manner as other costs. 
    (c)  Disclosure of Appointment. In the exercise of its discretion, the court may authorize disclosure to the jury of the fact that the court appointed the expert witness. 
    (d)  Parties' Experts of Own Selection. Nothing in this rule limits the parties in calling expert witnesses of their own selection.