Mateer earned his Bachelor of Artswith honors from Dickinson College and his Juris Doctor with honors from the Dedman School of Law. He spent nearly 20 years litigating in private practice, where he handled a range of trial and appellate matters. He then became general counsel and executive vice president of the First Liberty Institute. In two 2015 speeches, he described the issue of transgender children as a deception and "part of Satan's plan". He also spoke in opposition to state bans on conversion therapy at a conference hosted by Kevin Swanson, a pastor who preaches that the Biblical punishment for homosexuality is death. Mateer said that the legalization of same-sex marriage could lead to the legalization of polygamy and bestiality. Mateer currently serves as the First Assistant Attorney General of Texas, where he oversees the Office of Attorney General of Texas, including supervision of the state's active litigation matters.
Failed nomination to District Court
On September 7, 2017, President Donald Trump nominated Mateer to serve as a United States District Judge of the United States District Court for the Eastern District of Texas, to the seat vacated by Judge Richard A. Schell, who assumed senior status on March 10, 2015. Mateer was recommended to the White House by Senators John Cornyn and Ted Cruz. After Mateer's remarks about transgender children being part of "Satan's plan" and his support for conversion therapy were publicized in late September 2017, John Cornyn, the senior Republican Senator from Texas and then- Senate Majority Whip, expressed skepticism about Mateer's suitability to sit on the federal bench. Cornyn and members of a committee that screens Texas judicial candidates said that Mateer had not disclosed the statements. Cruz said that he still supported Mateer's nomination. In December 2017, Mateer's nomination for the federal judiciary was withdrawn. On January 3, 2018, his nomination was returned to the President under Rule XXXI, Paragraph 6 of the United States Senate. On January 8, 2018, the White House renominated 21 of 26 federal judicial nominees who had been returned by the U.S. Senate. Mateer was not among the 21 individuals who were renominated.
