The Texas Supreme Court reversed a lower court decision in the estate case of *In re Estate of Guadalupe Lopez, Sr.*, ruling that a former family court judge's expert testimony on informal marriage was improperly admitted and warranted a new trial.

The case centered on whether the deceased, Guadalupe Lopez Sr., was informally married to another party, a determination that would affect the distribution of his estate. The dispute reached the Texas Supreme Court after the Fourth District Court of Appeals reviewed the trial court's decision.

At the heart of the court's decision was the testimony of a former family court judge who served as an expert witness. The expert opined on the central disputed issue in the case, testifying before the jury that, in her view, the parties were informally married. The court noted that she expressed this opinion "repeatedly and emphatically" throughout her testimony.

The Texas Supreme Court found multiple problems with allowing this expert testimony. First, the court determined that none of the relevant evidence was "technical, specialized, or otherwise beyond an ordinary person's understanding." The evidence consisted of testimony from witnesses about the couple's relationship, their living arrangements, and their public presentation as a married couple - all matters within the jury's competence to evaluate.

Second, the court emphasized that the expert's background as a former family court judge gave her testimony inappropriate weight with the jury. The court noted that her judicial experience, while impressive, did not qualify her to render expert opinions on factual determinations that were properly within the jury's province.

The court concluded that admitting this expert testimony constituted harmful error that affected the outcome of the trial. As a result, the Texas Supreme Court ordered a new trial in the estate matter, emphasizing the importance of proper gatekeeping regarding expert testimony in civil proceedings.