In City of San Antonio v. Higle, 685 S.W.2d 682 (Tex. App.-San Antonio 1984, writ ref'd n.r.e.) a police officer claimed immunity under TEX. CIV. STAT. ANN. art. 6252-19 14(8) (Vernon 1970 and Vernon Supp. 1982-1983) , which required him to demonstrate his action was in compliance with the laws and ordinances applicable to the emergency action. Id. at 687. The court held that the defendant police officer was not entitled to immunity because he did not show compliance with the laws or ordinances as required. Id. Instead, the evidence demonstrated that the officer acted in violation of prescribed departmental procedures. Id. Generally, government employees are entitled to official immunity from suit arising from the performance of their: (1) discretionary duties in; (2) good faith as long as they are; (3) acting within the scope of their authority. See Chambers, 883 S.W.2d at 653 (emphasis added). Official immunity is an affirmative defense. See id. An "affirmative defense" is a plea in bar or a defense in avoidance, rather than a defense in denial. See Gorman v. Life Ins. Co. of North America, 811 S.W.2d 542, 546 (Tex.), cert. denied, 502 U.S. 824, 116 L. Ed. 2d 60, 112 S. Ct. 88 (1991). The nature of an affirmative defense presupposes a prima facie claim. See id; see also 58 TEX. JUR. 3d Pleading 197 (1996) (citing authorities therein).