Georgia Code Title 9. Civil Practice § 9-14-51

All grounds for relief claimed by a petitioner for a writ of habeas corpus shall be raised by a petitioner in his original or amended petition. Any grounds not so raised are waived unless the Constitution of the United States or of this state otherwise requires or unless any judge to whom the petition is assigned, on considering a subsequent petition, finds grounds for relief asserted therein which could not reasonably have been raised in the original or amended petition.