According to Rules 701-706 of Federal Rules of Evidence, a witness who is qualified as an expert by knowledge, skill, experience, training, or education may testify in the form of an opinion or otherwise if the expert’s scientific, technical, or other specialized knowledge will help the trier of fact to understand the evidence or to determine a fact in issue (a); the testimony is based on sufficient facts or data (b); the testimony is the product of reliable principles and methods (c); and the expert has reliably applied the principles and methods to the facts of the case (d). (a) On a party’s motion or on its own, the court may order the parties to show cause why expert witnesses should not be appointed and may ask the parties to submit nominations. The court may appoint any expert that the parties agree on and any of its own choosing. But the court may only appoint someone who consents to act. The court must inform the expert of the expert’s duties. The court may do so in writing and have a copy filed with the clerk or may do so orally at a conference in which the parties have an opportunity to participate. The expert must advise the parties of any findings the expert makes; may be deposed by any party; may be called to testify by the court or any party; and may be cross-examined by any party, including the party that called the expert. The expert is entitled to a reasonable compensation, as set by the court. Parties’ Choice of their own experts. This rule does not limit a party in calling its own experts. If a witness is not testifying as an expert, testimony in the form of an opinion is limited to one that is rationally based on the witness’s perception (a); helpful to clearly understanding the witness’s testimony or to determining a fact in issue (b); and not based on scientific, technical, or other specialized knowledge (c).