FAMILY CODE SECTION 7540-7541
7540. Except as provided in Section 7541, the child of a wife
cohabiting with her husband, who is not impotent or sterile, is
conclusively presumed to be a child of the marriage.
7541. (a) Notwithstanding Section 7540, if the court finds that the
conclusions of all the experts, as disclosed by the evidence based
on blood tests performed pursuant to Chapter 2 (commencing with
Section 7550), are that the husband is not the father of the child,
the question of paternity of the husband shall be resolved
(b) The notice of motion for blood tests under this section may be
filed not later than two years from the child’s date of birth by the
husband, or for the purposes of establishing paternity by the
presumed father or the child through or by the child’s guardian ad
litem. As used in this subdivision, “presumed father” has the meaning
given in Sections 7611 and 7612.
(c) The notice of motion for blood tests under this section may be
filed by the mother of the child not later than two years from the
child’s date of birth if the child’s biological father has filed an
affidavit with the court acknowledging paternity of the child.
(d) The notice of motion for blood tests pursuant to this section
shall be supported by a declaration under oath submitted by the
moving party stating the factual basis for placing the issue of
paternity before the court.
(e) Subdivision (a) does not apply, and blood tests may not be
used to challenge paternity, in any of the following cases:
(1) A case that reached final judgment of paternity on or before
September 30, 1980.
(2) A case coming within Section 7613.
(3) A case in which the wife, with the consent of the husband,
conceived by means of a surgical procedure.