does not necessarily apply when either the issues or the facts presented in successive appeals are not substantially the same as those involved in the first trial. Pitman v. Lightfoot, 937 S.W.2d 496, 513 (Tex. App.—San Antonio 1996, writ denied). Moreover, it is an exception to the law of the case doctrine that the original decision was clearly erroneous. Briscoe, 102 S.W.3d at 716. Although an original proceeding is not an “appeal,” the law of the case doctrine applies when an issue has been resolved on the merits in a prior mandamus proceeding, even though it does not proceed to a court of last resort or the issues raised have not been resolved by a court of last resort. See In re Guardianship of Cantu de Villarreal, 330 S.W.3d 11, 20-21 (Tex. App.—Corpus Christi 2010, no pet.) (<HOLDING>); BSP Mktg., Inc. v. Standard Waste Sys., Ltd.,
holding law of the case doctrine prevented reconsideration of issue decided in earlier mandamus petition holding that under the law of the case doctrine an issue of fact or law decided on appeal may not be reexamined by the appellate court on a subsequent appeal recognizing in the context of a petition for a writ of mandamus that although the district court retained jurisdiction over the case following the governments mandamus petition the district court justifiably could defer trial until resolution of the appellate proceedings had the government prevailed on the merits of the mandamus petition  the trial strategies of the government as well as the defense would surely have been altered holding that law of the case prevented the new jersey district court from redetermining jurisdictional issue previously decided by the district of columbia district court and noting that the principles of comity among courts of the same level of the federal system provide further reason why  an issue already decided by a court of equal authority should not be reexamined holding that law of the case acts as a bar only when the issue in question was actually considered and decided by the first court