The Oklahoma Bar Journal January 2026

F amily L aw Thirty Years of Thielenhaus : The Dubious Origins of That Case’s Burden of Proof Requirement By Ryan J. Reaves T HERE ARE FEW, IF ANY, CASES IN OKLAHOMA FAMILY LAW more frequently cited than Thielenhaus v. Thielenhaus . 1 This decision was published (as modified) on Sept. 1, 1995 – just over 30 years ago. While Thielenhaus may be cited for a great many issues, its central and most enduring holding is the one related to in-marriage enhancement of a separate asset. After 30 years, it seemed only fitting to take a fresh look at Thielenhaus and consider whether there might be a need for a different approach.

increase in value due to market forces and 3) the increase in value related to the funds, skills and efforts of the parties. 7 This, in effect, created a presumption that the increase in the value of sepa rate property during marriage is separate property. Since this rule was pronounced 30 years ago, it has become the foundation of Oklahoma’s law on in-marriage enhancement of separate assets. However, placing the burden of proof in a manner designed to protect the separate estate from marital claims is highly unusual. Oklahoma marital property law contains a number of evidentiary presumptions, and virtually every one of those supports the acquisi tion of marital property rather than the protection of separate prop erty. 8 Oklahoma law presumes that

In Thielenhaus , the late Justice Marion Opala synthesized exist ing case law to create a clear and ostensibly workable rule govern ing the division of premarital property that has increased in value during the marriage: Where, as here, a spouse brings separate property to the mar riage, its increased or enhanced value, produced by investment managed by neither spouse or by appreciation, inflation, changing economic conditions, or circum stances beyond the parties’ control , cannot be treated as a divisible marital asset unless, of course, there be proof that the increase resulted from efforts, skills or funds of either spouse. The non-owning spouse’s interest in the increased separate estate of the

other, when established through efforts, skills or expended funds, stands confined to the enhanced value of that separate property . 2

The rule set forth in Thielenhaus was largely a combination of the rules set out in Templeton v. Templeton , 3 Moyers v. Moyers 4 and May v. May . 5 In that sense, it was largely a restatement of existing law. However, the Thielenhaus opin ion included a far more significant departure from existing law when it advised, “The burden is upon the non-owning spouse to show that the enhancement is the result of either spouse’s endeavors.” 6 Further, Thielenhaus held that this burden of proof extended to the “three critical value-assessment elements,” which are: 1) the value at the date of marriage, 2) the

Statements or opinions expressed in the Oklahoma Bar Journal are those of the authors and do not necessarily reflect those of the Oklahoma Bar Association, its officers, Board of Governors, Board of Editors or staff.

16 | JANUARY 2026

THE OKLAHOMA BAR JOURNAL