(a) General Rule. Every person is competent to be a witness except as otherwise provided in these rules. The following witnesses shall be incompetent to testify in any proceeding subject to these rules:
(1) Insane persons. Insane persons who, in the opinion of the court, are in an insane condition of mind at the time when they are offered as a witness, or who, in the opinion of the court, were in that condition when the events happened of which they are called to testify.
(2) Children. Children or other persons who, after being examined by the court, appear not to possess sufficient intellect to relate transactions with respect to which they are interrogated.
(b) “Dead Man Rule” in Civil Actions. In civil actions by or against executors, administrators, or guardians, in which judgment may be rendered for or against them as such, neither party shall be allowed to testify against the others as to any oral statement by the testator, intestate or ward, unless that testimony to the oral statement is corroborated or unless the witness is called at the trial to testify thereto by the opposite party; and, the provisions of this article shall extend to and include all actions by or against the heirs or legal representatives of a decedent based in whole or in part on such oral statement. Except for the foregoing, a witness is not precluded from giving evidence of or concerning any transaction with, any conversations with, any admissions of, or statement by, a deceased or insane party or person merely because the witness is a party to the action or a person interested in the event thereof. The trial court shall, in a proper case, where this rule prohibits an interested party or witness from testifying, instruct the jury that such person is not permitted by the law to give evidence relating to any oral statement by the deceased or ward unless the oral statement is corroborated or unless the party or witness is called at the trial by the opposite party.