Rule 601. General Rule of Competency

(A) General rule Every person is competent to be a witness except as otherwise provided in these rules.

(B) Disqualification of witness in general A person is disqualified to testify as a witness when the court determines that the person is any of the following:

(1) Incapable of expressing himself or herself concerning the matter as to be understood, either directly or through interpretation by one who can understand him or her;

(2) Incapable of understanding the duty of a witness to tell the truth;

(3) A spouse testifying against the other spouse charged with a crime except when either of the following applies:

(a) A crime against the testifying spouse or a child of either spouse is charged;

(b) The testifying spouse elects to testify.

(4) An officer, while on duty for the exclusive or main purpose of enforcing traffic laws, arresting or assisting in the arrest of a person charged with a traffic violation punishable as a misdemeanor where the officer at the time of the arrest was not using a properly marked motor vehicle as defined by statute or was not wearing a legally distinctive uniform as defined by statute;

(5) A person giving expert testimony on the issue of liability in any medical claim, as defined in R.C. 2305.113, asserted in any civil action against a physician, podiatrist, or hospital arising out of the diagnosis, care, or treatment of any person by a physician or podiatrist, unless all the following apply:

(a) The person testifying is licensed to practice medicine and surgery, osteopathic medicine and surgery, or podiatric medicine and surgery by the state medical board or by the licensing authority of any state;

(b) The person devotes at least one-half of his or her professional time to the active clinical practice in his or her field of licensure, or to its instruction in an accredited school, at either the time the negligent act is alleged to have occurred or the date the claim accrued;

(c) The person practices in the same or a substantially similar specialty as the defendant. The court shall not permit an expert in one medical specialty to testify against a health care provider in another medical specialty unless the expert shows both that the standards of care and practice in the two specialties are similar and that the expert has substantial familiarity between the specialties. If the person is certified in a specialty, the person must be certified by a board recognized by the American board of medical specialties or the American board of osteopathic specialties in a specialty having acknowledged expertise and training directly related to the particular health care matter at issue. Nothing in this division shall be construed to limit the power of the trial court to adjudge the testimony of any expert witness incompetent on any other ground, or to limit the power of the trial court to allow the testimony of any other witness, on a matter unrelated to the liability issues in the medical claim, when that testimony is relevant to the medical claim involved. This division shall not prohibit other medical professionals who otherwise are competent to testify under these rules from giving expert testimony on the appropriate standard of care in their own profession in any claim asserted in any civil action against a physician, podiatrist, medical professional, or hospital arising out of the diagnosis, care, or treatment of any person.

(6) As otherwise provided in these rules.