Ohio Rev. Code Ann. § 3111.03 – Presumption of paternity

(A) A man is presumed to be the natural father of a child under any of the following circumstances:
1. (1) The man and the child's mother are or have been married to each other, and the child is born during the marriage or is born within three hundred days after the marriage is terminated by death, annulment, divorce, or dissolution or after the man and the child's mother separate pursuant to a separation agreement.
2. (2) The man and the child's mother attempted, before the child's birth, to marry each other by a marriage that was solemnized in apparent compliance with the law of the state in which the marriage took place, the marriage is or could be declared invalid, and either of the following applies:
  1. (a) The marriage can only be declared invalid by a court and the child is born during the marriage or within three hundred days after the termination of the marriage by death, annulment, divorce, or dissolution;
  2. (b) The attempted marriage is invalid without a court order and the child is born within three hundred days after the termination of cohabitation.
3. (3) An acknowledgment of paternity has been filed pursuant to section 3111.23 or former section 5101.314 of the Revised Code and has not become final under former section 3111.211 or 5101.314 or section 2151.232, 3111.25, or 3111.821 of the Revised Code.
(B) A presumption that arises under this section can only be rebutted by clear and convincing evidence that includes the results of genetic testing, except that a presumption that is conclusive as provided in division (A) of section 3111.95 or division (B) of section 3111.97 of the Revised Code cannot be rebutted. An acknowledgment of paternity that becomes final under section 2151.232, 3111.25, or 3111.821 of the Revised Code is not a presumption and shall be considered a final and enforceable determination of paternity unless the acknowledgment is rescinded under section 3111.28 or 3119.962 of the Revised Code. If two or more conflicting presumptions arise under this section, the court shall determine, based upon logic and policy considerations, which presumption controls.
(C)
1. (1) Except as provided in division (C)(2) of this section, a presumption of paternity that arose pursuant to this section prior to March 22, 2001, shall remain valid on and after that date unless rebutted pursuant to division (B) of this section. This division does not apply to a determination described in division (B)(3) of this section as division (B)(3) of this section existed prior to March 22, 2001.
2. (2) A presumption of paternity that arose prior to March 22, 2001, based on an acknowledgment of paternity that became final under former section 3111.211 or 5101.314 or section 2151.232 of the Revised Code is not a presumption and shall be considered a final and enforceable determination of paternity unless the acknowledgment is rescinded under section 3111.28 or 3119.962 of the Revised Code.