Mackley v. Openshaw, 456 P.3d 742

Adam Mackley conceived a child with Adrienne Openshaw while she remained married to Colton Barney; Mackley filed a paternity petition before the child’s birth.
After birth, genetic testing showed a 99.99% probability the child was Mackley’s. Mother and Mackley executed a stipulation and a Voluntary Declaration of Paternity form; Husband (Barney) also signed the form’s section labeled “Denial of Paternity” at the health department.
The district court initially stayed Mackley’s case, issued declaratory judgment recognizing Husband as the child’s legal father, and dismissed Mackley’s paternity petition. Mackley obtained relief under Rule 60(b) and the prior orders were vacated.
Husband moved to rescind his denial of paternity, claiming mutual and unilateral mistake of fact (and duress); after an evidentiary hearing the district court granted rescission, reinstated declaratory judgment for Husband, and dismissed Mackley’s petition.
The Utah Supreme Court held that the district court erred in allowing rescission because the claimed mistake concerned the legal consequences of signing the form (a mistake of law), not a factual mistake; the rescission was reversed and the denial remains in effect, rendering the standing issue moot.

Issue	Plaintiff's Argument (Mackley)	Defendant's Argument (Mother/Husband)	Held
Whether Husband could rescind his voluntary denial of paternity based on mutual or unilateral mistake	Rescission was improper because any alleged mistake was legal (about consequences), not factual; therefore the denial should remain	Rescission was proper because all parties mistakenly believed the form’s purpose was to add Mackley to the birth certificate and did not understand the legal effect; health-dept conduct contributed to the mistake	Reversed: rescission improperly allowed. The claimed mistake was one of law (legal consequences), not fact; signatory has duty to read/understand the form, so denial remains in effect.
Whether Mackley had standing under the UUPA to challenge presumed paternity	Mackley argued the UUPA grants alleged fathers standing to rebut a presumption of paternity and challenge a presumed father	Mother argued that when a child is born during a marriage and has a presumed father, an alleged father lacks statutory standing (relying on Schoolcraft-type policy)	Moot in this case because the denial remains in effect. Court noted its companion decision (Castro v. Lemus) would grant standing to alleged fathers if rescission had been valid.

Briggs v. Liddell, 699 P.2d 770 (Utah 1985) (elements for rescission based on unilateral mistake)
John Call Eng’g, Inc. v. Manti City Corp., 743 P.2d 1205 (Utah 1987) (duty to read contract; ignorance of law not a defense)
Burningham v. Westgate Resorts, Ltd., 317 P.3d 445 (Utah Ct. App. 2013) (mutual mistake can support equitable rescission)
Deep Creek Ranch, LLC v. Utah State Armory Bd., 178 P.3d 886 (Utah 2008) (standard of review for factual findings and legal conclusions on mistake)
In re J.W.F. (Schoolcraft), 799 P.2d 710 (Utah 1990) (prior common-law test and policy considerations for paternity challenges)
Bergmann v. Bergmann, 428 P.3d 89 (Utah Ct. App. 2018) (mutual mistake requires clear-and-convincing proof)