The appellate standard of review in summary judgment is de novo. Kirkpatrick v. Chrysler Corp., 1996 OK 136, P2, 920 P.2d 122, 124. This means without deference. Hulett v. First Nat. Bank & Trust Co. in Clinton, 1998 OK 21, 956 P.2d 879; see Salve Regina College v. Russell, 499 U.S. 225, 111 S. Ct. 1217, 113 L. Ed. 2d 190 (1991). The pleadings and evidentiary materials will be examined to determine what facts are material and whether there is a substantial controversy as to one material fact. Sperling v. Marler, 1998 OK 81, 963 P.2d 577; Malson v. Palmer Broadcasting Group, 1997 OK 42, 936 P.2d 940. All inferences and conclusions to be drawn from the materials must be viewed in a light most favorable to the non-moving party. Carmichael v. Beller, 1996 OK 48, 914 P.2d 1051. Even though the facts may not be controverted, if reasonable persons may draw different conclusions from these facts, summary judgment must be denied. Bird v. Coleman, 1997 OK 44, 939 P.2d 1123. Summary judgment is proper only if the record reveals uncontroverted material facts failing to support any legitimate inference in favor of the nonmoving party. N.C. Corff Partnership, Ltd. v. OXY USA, Inc., 1996 OK CIV APP 92, 929 P.2d 288. When genuine issues of material fact exist, summary judgment should be denied and the question becomes one for determination by the trier of fact. Brown v. Oklahoma State Bank & Trust Co. of Vinita, 1993 OK 117, 860 P.2d 230; Flowers v. Stanley, 1957 OK 237, 316 P.2d 840. Because the trial court has the limited role of determining whether there are any such issues of fact, it may not determine fact issues on a motion for summary judgment nor may it weigh the evidence. Stuckey v. Young Exploration Co., 1978 OK 128, P15, 586 P.2d 726, 730. One who defends against a claim and who does not bear the burden of proof is not required to negate the plaintiff's claims or theories in order to prevail on motion for summary judgment. When, as here, a defendant moves for summary judgment without relying upon an affirmative defense the defendant must show: that no substantial factual controversy exists as to at least one fact essential to plaintiff's theory of the cause of action; that the fact is in defendant's favor. Once a defendant has introduced evidentiary materials to establish these points, the plaintiff then has the burden of showing that evidence is available which justifies a trial of the issue. Akin v. Missouri Pacific R.R. Co., 1998 OK 102, P8, 977 P.2d 1040, 1044; Stephens v. Yamaha Motor Co., Ltd. Japan, 1981 OK 42, P11, 627 P.2d 439, 441; Runyon v. Reid, 1973 OK 25, PP12-13, 510 P.2d 943, 946.